T1 vs T4 vs SM vs AS pace at Buttonwillow Raceway Park
Quickest here:T1 1:46.465 Ian Barberi, Cal Club 2025 qualifying · T4 1:58.339 Oscar Jackson, Cal Club 2025 qualifying · SM 2:00.831 William Wallis, Cal Club 2025 qualifying · AS 1:55.849 Roger Eagleton, Cal Club 2025 race
T1T4SMASsolid race · dashed qualifying · slower is lower
T1T4SMASsolid race · dashed qualifying · each class's best lap as a share of T1's at the same event (the reference class, changeable above); 100% is level, higher is quicker
Event
T1
T4
SM
AS
Qual best
Race best
Trap
Qual best
Race best
Trap
vs T1
% of T1
Qual best
Race best
Trap
vs T1
% of T1
Qual best
Race best
Trap
vs T1
% of T1
Cal Club 2026 CALCL262026-02-21
1:59.760Ed Gless · only car+13.295s (+12.49%)
1:59.123Ed Gless · only car+11.689s (+10.88%)
120.7Ed Gless-18.6 mph (-13.3%)
2:01.678Izzy Sanchez · fastest of 5 · top 5 within 5.9s+3.339s (+2.82%)
2:01.157Izzy Sanchez · fastest of 5 · top 5 within 7.2s+1.235s (+1.03%)
135.5Izzy Sanchez+27.2 mph (+25.1%)
+2.034squal +1.918s
101.7%qual 101.6%
2:01.392Ryan Busk · fastest of 18 · top 5 within 0.8s+0.561s (+0.46%)
2:02.486William Rasmussen · fastest of 18 · top 5 within 1.3s+0.836s (+0.69%)
127.3Sam Rezai+23.4 mph (+22.6%)
+3.363squal +1.632s
102.8%qual 101.4%
1:56.812Ross Murray · fastest of 2+0.367s (+0.32%)
1:56.314Ross Murray · fastest of 2+0.465s (+0.40%)
135.2Ross Murray+26.5 mph (+24.4%)
-2.809squal -2.948s
97.6%qual 97.5%
46 rule changes (T1: 13, T4: 19, SM: 3, AS: 11)7 cars added · 7 weight · 5 induction · 4 tyres & wheels · 2 removed · 2 suspension & brakes · 1 aero · 18 wording · AS Chevy LS adds Edelbrock Performer RPM 71187 intake manifold with MSD 6014 ignition and 4776 Holly carburetor as spec line option. · T1 Corvette C6 LS1/LS6 Spec Line reinstated: 3200 lbs minimum weight, 70mm restrictor required. · Ford Mustang V6 (05-14) removed from T4 Spec Lines. · T4 Mustang 4.0 V6 tire size increases from 245 to 255. · T2-T4 adjustable toe links now allow performance alternative bushings and spherical bearings, previously prohibited except in specified examples. · AS Ford Mustang Restricted Prep engines lose 3 mm restrictor plate, from 64 mm to 61 mm. · T1 Spec Line restrictor changes from 70mm flat plate to unspecified new specification. · T2, T3, T4 cars may relocate under-dash electronics and fuse boxes for access after roll cage installation. · T4 Performance now permits 1-piece alternative rotors matching spec line sizes; alternate brake kits allowed same. · AS Ford Mustang GT 94-04 Restricted Prep Engine now permits Ford Motorsport M-6250-F303 camshaft. · Unable to summarize: letter states intent but provides no actual rule changes to S2000 specification. · T1 non-GT4 cars: multiple restrictors enlarged (70mm to 73mm, 75mm to 78mm, 55mm to 60mm, 61mm to 70mm); one weight increased to 3600. · T1 BMW M3 E92 (08-13) Spec Line 1090 removed entirely. · Dodge/Plymouth Neon ACR SOHC/DOHC 95-99 newly classified T4 at 2350 lbs minimum weight. · AS Cadillac CTS-V 04-07 Restricted Prep weight reduced 50 lbs to 3400. · T4 Mini Cooper S R53 02-06 gear ratios changed to 12.79, 7.79, 5.65, 4.62, 3.83, 3.13 or 11.42, 7.18, 5.39, 4.40, 3.65, 2.96. · Chevrolet Cobalt SS Sport Coupe 06-10 reinstated to T4 with 2384cc engine, 2628 restrictor, 2700 lbs minimum weight. · Mercedes C230 Kompressor 2002-2005 classified in T4 at 3240 lbs with 17-inch wheels and 300/290 mm brakes. · T3 and T4 Mazda MX-5 Miata models add approved gear kit PT#-0000-02-6100 to notes. · T4 Mazda MX-5 Miata/Club 16-18 wheel size changed to 17 x 7.5 inches. · T4 Mazda MX-5 Miata/Club/RF (19-24) and (16-18) remove discontinued hardtop part #0000-07-5901; T3 MX-5 Miata (16-18) and Global Cup ND (16-21) same. · T2, T3, T4 Spec Lines table header changed from T2 to ET. · AS Ford Mustang GT 5.0 2018- weight reduced from 3600 to 3525 lbs. · T4 now permits B-Spec and C-Spec cars to compete in the class. · AS Ford Mustang GT 05-14 Restricted Prep Engine gains alternative gear ratios: 3.66, 2.43, 1.69, 1.32, 1.00, .65 · SMX drivers must submit data acquisition files on time or face suspension and $250 fine. · SMX penalty language clarified: level 1 and 3 infractions may carry $1,000 fine; level 2 and 4 may carry $500 fine. · T4 Ford Mustang V6 05-14 weight drops from 3400 to 3300 lbs. · T4 Scion FR-S and Subaru BRZ Solo Spec allow any 200TW 225/45/17 or 215/45/17 DOT tire. · AS Ford Mustang GT 5.0L (15-17) flat plate restrictor reduced from 67mm to 64mm. · AS LS1/LS6 5.3L truck engine gains four approved intake part numbers: 12561269, 88894095, 89017363, 89017364. · SM cars limited to one set of Hoosier SM 7.5 P205/50/ZR17 per Super Tour event weekend for dry sessions. · Porsche 981 GT4 Clubsport added to T1 as spec line 4085, minimum weight 3100 lbs with driver. · T1 Honda S2000 minimum weight reduced from 2950 lbs to 2900 lbs. · T1 BMW E46 M3 permits BMW #GS7D36SG aftermarket sequential transmission in SL# 1060 and 1070. · T1 BMW M3 E92 minimum weight reduced to 3300 lbs. · T1 Mustang Darkhorse R gets 315 front and rear tyres, loses 500 lbs minimum weight to 3600. · T4 Ford Mustang V6 05-14 allows GT 8.8 rear axle or 7.5 axle with 3.45:1 ratio. · T4 Ford Mustang V6 05-14 now permits OEM style rear deck spoiler similar to Laguna/CS packages. · AS Flotek Head plunge cut dimensions figure updated in GCR Section 9.1.6. · AS class notes cleanup: multiple Camaro, Firebird, CTS-V, Challenger, Mustang specs and fuel cell/ECM/head restrictions removed. · Cadillac CT4-V Blackwing added to T1 Spec Line 1115, 3564cc, 3750 lbs minimum weight. · AS Spec Lines removes ECM flexibility restriction from five Cadillac and Chevrolet/Pontiac V8 models. · T1 Mustang Spec 1430 restrictor opens 60mm to 65mm; Spec 1460 weight rises to 3500 lbs, restrictor 70mm; Corvette 1190 restrictor opens 67mm to 70mm; BMW 1090 restrictor narrows 40mm to 35mm; BMW 1100 weight rises to 3350 lbs.showhide
AS Edelbrock manifold (& timing kit) to Chevy LS Spec Lines Request #39055cars addedcars addedAS Chevy LS adds Edelbrock Performer RPM 71187 intake manifold with MSD 6014 ignition and 4776 Holly carburetor as spec line option.
T1 LS1 into Corvette C6 Spec Line Request #39716cars addedcars addedT1 Corvette C6 LS1/LS6 Spec Line reinstated: 3200 lbs minimum weight, 70mm restrictor required.
T4 T4 and T3 Feedback #39230removedremovedFord Mustang V6 (05-14) removed from T4 Spec Lines.
T4 T4 Mustang 4.0 #39489tyres & wheelsfasterT4 Mustang 4.0 V6 tire size increases from 245 to 255.
T4 Allow Alt Bushing Material in Toe Links #39607suspension & brakesfasterT2-T4 adjustable toe links now allow performance alternative bushings and spherical bearings, previously prohibited except in specified examples.
AS Restrictor Plate Change for Gen 2 Ford Coyote Engine #39501inductionslowerAS Ford Mustang Restricted Prep engines lose 3 mm restrictor plate, from 64 mm to 61 mm.
T1 additional T1 adjustment #39520inductionunclearT1 Spec Line restrictor changes from 70mm flat plate to unspecified new specification.
T4 Alternate Placement of Fuse Panel and Electronics Request #39370wordingwordingT2, T3, T4 cars may relocate under-dash electronics and fuse boxes for access after roll cage installation.
T4 Clarify T4 Brake Rotor Allowance #39503suspension & brakessuspension & brakesT4 Performance now permits 1-piece alternative rotors matching spec line sizes; alternate brake kits allowed same.
AS 1994 Mustang Spec Line Request #39104wordingunclearAS Ford Mustang GT 94-04 Restricted Prep Engine now permits Ford Motorsport M-6250-F303 camshaft.
T1 Keep S2000 Classification #39344wordingunclearUnable to summarize: letter states intent but provides no actual rule changes to S2000 specification.
T1 Correcting and updating T1 GT4 spec lines #39394weight
T1 BOP adjustments to non GT4 T1 cars #39406induction +100 lbsfasterT1 non-GT4 cars: multiple restrictors enlarged (70mm to 73mm, 75mm to 78mm, 55mm to 60mm, 61mm to 70mm); one weight increased to 3600.
T1 Remove T1 Spec Line #39407removedremovedT1 BMW M3 E92 (08-13) Spec Line 1090 removed entirely.
AS Cadillac CTS-V BOP Weight Change #38640weight -50 lbsfasterAS Cadillac CTS-V 04-07 Restricted Prep weight reduced 50 lbs to 3400.
T4 02-06 Mini Cooper Gear Ratios #38966wordingunclearT4 Mini Cooper S R53 02-06 gear ratios changed to 12.79, 7.79, 5.65, 4.62, 3.83, 3.13 or 11.42, 7.18, 5.39, 4.40, 3.65, 2.96.
T4 Reinstatement of the 2005-2010 Cobalt into T4 #38987cars addedcars addedChevrolet Cobalt SS Sport Coupe 06-10 reinstated to T4 with 2384cc engine, 2628 restrictor, 2700 lbs minimum weight.
T4 Request to Classify Mercedes C230K #39080cars addedcars addedMercedes C230 Kompressor 2002-2005 classified in T4 at 3240 lbs with 17-inch wheels and 300/290 mm brakes.
T4 ND Gearset Request for T4 #39166wordingwordingT3 and T4 Mazda MX-5 Miata models add approved gear kit PT#-0000-02-6100 to notes.
T4 E&O wheel size on ND #39168tyres & wheelsunclearT4 Mazda MX-5 Miata/Club 16-18 wheel size changed to 17 x 7.5 inches.
T4 ND Spec Lines Wrong PT#'s #39170wordingwordingT4 Mazda MX-5 Miata/Club/RF (19-24) and (16-18) remove discontinued hardtop part #0000-07-5901; T3 MX-5 Miata (16-18) and Global Cup ND (16-21) same.
T4 Incorrect Touring Heading #38451wordingwordingT2, T3, T4 Spec Lines table header changed from T2 to ET.
AS RE: Previous Letter 37695 Update #38245weight -75 lbsfasterAS Ford Mustang GT 5.0 2018- weight reduced from 3600 to 3525 lbs.
T4 Allow B-Spec cars to run in T4 #38439wordingwordingT4 now permits B-Spec and C-Spec cars to compete in the class.
AS Errors and Omissions #38234wordingwordingAS Ford Mustang GT 05-14 Restricted Prep Engine gains alternative gear ratios: 3.66, 2.43, 1.69, 1.32, 1.00, .65
SM SMX Data Submission - Penalties #38248wordingwordingSMX drivers must submit data acquisition files on time or face suspension and $250 fine.
SM Committee) SMX Penaly Clarification updated language #38337wordingwordingSMX penalty language clarified: level 1 and 3 infractions may carry $1,000 fine; level 2 and 4 may carry $500 fine.
T4 T4 Mustang #38059weight -100 lbsfasterT4 Ford Mustang V6 05-14 weight drops from 3400 to 3300 lbs.
T4 SSC tire allowance #38216tyres & wheelstyres & wheelsT4 Scion FR-S and Subaru BRZ Solo Spec allow any 200TW 225/45/17 or 215/45/17 DOT tire.
AS Errors and Omission #38055inductionslowerAS Ford Mustang GT 5.0L (15-17) flat plate restrictor reduced from 67mm to 64mm.
AS Request to Add LS1/LS6 Intakes for 5.3L Truck Engine EnO #38197wordingwordingAS LS1/LS6 5.3L truck engine gains four approved intake part numbers: 12561269, 88894095, 89017363, 89017364.
SM Clarify Tire Marking Regs #38005wordingwordingSM cars limited to one set of Hoosier SM 7.5 P205/50/ZR17 per Super Tour event weekend for dry sessions.
T1 Acceptance of Porsche 981 GT4 Clubsport into T1 #36664cars addedcars addedPorsche 981 GT4 Clubsport added to T1 as spec line 4085, minimum weight 3100 lbs with driver.
T1 Request to Restore T1 Honda S2000 to Proper Weights #37644weight -50 lbsfasterT1 Honda S2000 minimum weight reduced from 2950 lbs to 2900 lbs.
T1 DCT Transmission in E46 #37964wordingwordingT1 BMW E46 M3 permits BMW #GS7D36SG aftermarket sequential transmission in SL# 1060 and 1070.
T1 Reduce E92 M3 Minimum Weight to 3050 #38092weightfasterT1 BMW M3 E92 minimum weight reduced to 3300 lbs.
T1 Finalize Spec Line for T1 Darkhorse #38106tyres & wheelsfasterT1 Mustang Darkhorse R gets 315 front and rear tyres, loses 500 lbs minimum weight to 3600.
T4 Correct Ring and Pinion Ratio to T3, Sorry I Mean T4 3.7 V6 Stang #38041wordingwordingT4 Ford Mustang V6 05-14 allows GT 8.8 rear axle or 7.5 axle with 3.45:1 ratio.
T4 T4 Mustang #38058aeroaeroT4 Ford Mustang V6 05-14 now permits OEM style rear deck spoiler similar to Laguna/CS packages.
AS Flotek Head Plunge Cut Inconsistencies #37502wordingunclearAS Flotek Head plunge cut dimensions figure updated in GCR Section 9.1.6.
AS Notes clean up #37693wordingwordingAS class notes cleanup: multiple Camaro, Firebird, CTS-V, Challenger, Mustang specs and fuel cell/ECM/head restrictions removed.
T1 Cadillac CT4-V Blackwing #38003cars addedcars addedCadillac CT4-V Blackwing added to T1 Spec Line 1115, 3564cc, 3750 lbs minimum weight.
AS Race memo #37902wordingunclearAS Spec Lines removes ECM flexibility restriction from five Cadillac and Chevrolet/Pontiac V8 models.
T1 Correct and make new T1 BOP adjustments. #37737weight +75 lbsunclearT1 Mustang Spec 1430 restrictor opens 60mm to 65mm; Spec 1460 weight rises to 3500 lbs, restrictor 70mm; Corvette 1190 restrictor opens 67mm to 70mm; BMW 1090 restrictor narrows 40mm to 35mm; BMW 1100 weight rises to 3350 lbs.
Cal Club 2025 CALCL252025-02-22
1:46.465Ian Barberi · fastest of 2
1:47.434Ian Barberi · fastest of 3 · top 3 within 11.8s
139.3Drew Delmonico
1:58.339Oscar Jackson · fastest of 5 · top 5 within 8.3s
1:59.922Oscar Jackson · fastest of 4 · top 4 within 7.3s
108.4Tony Kiratsous
+12.488squal +11.874s
111.6%qual 111.2%
2:00.831William Wallis · fastest of 16 · top 5 within 0.9s
2:01.650Nick Leverone · fastest of 16 · top 5 within 0.3s
103.9Evan Jacobs
+14.216squal +14.366s
113.2%qual 113.5%
1:56.445Roger Eagleton · fastest of 3 · top 3 within 4.0s
1:55.849Roger Eagleton · fastest of 4 · top 4 within 5.3s
108.7Roger Eagleton
+8.415squal +9.980s
107.8%qual 109.4%
128 rule changes (T1: 42, T4: 62, SM: 5, AS: 19)28 cars added · 17 weight · 8 tyres & wheels · 7 engine · 7 induction · 6 suspension & brakes · 3 aero · 2 removed · 44 wording · 6 other · T1 Mustang gains 125 lbs to 3600, restrictor shrinks 65mm to 60mm. Corvette gains 50 lbs to 3500, restrictor shrinks 70mm to 67mm. BMW deleted. · T1 E46 M3 Spec Line 1050 allows VAC Motorsports throttle body VAC-TB-S54 on 3.250L engine instead of Dinan. · T1 Chevrolet Corvette C8 (2023-23) minimum weight reduced from 3600 lbs to 3500 lbs. · T1 Chevrolet Camaro Gen 5 restrictor increases from 75mm to 80mm flat plate. · T1 Audi R8 GT4 Spec Line #4020 maximum tyre size changes to 315 DOT, 305/645, or 30/65-18 (f), 33/68-18 (r) Non-DOT. · T4 Ford Mustang V6 (05-14) final drive set to 3.45, GT/CS front bumper cover permitted with front fascia. · Ford SCCA Club Spec Mustang classified T3 at 3350 lbs with driver; Mazda SCCA Club Spec MX-5 classified T4 at 2500 lbs with driver. · AS Ford Mustang Coyote engines increase restrictor to 80mm from 64mm or 67mm. · AS Mustang GT 05-14 4.6L loses 300 lbs; 15-17 and 2018+ models lose 61mm and 60mm restrictors respectively. · AS class gear ratio options specified for multiple American muscle cars, including Cadillac CTS-V, Chevrolet Camaro, Ford Mustang, Dodge Challenger, and Pontiac GTO. · AS LS-engine cars gain ECU freedom; Camaro/Firebird 93-02 LS1 removes fuel cell location restriction. · T2, T3, T4 remove nine, nine, and thirty-six expired spec lines respectively, effective 2025-01-01. · T4 2016-2018 Mazda Miata MX-5 minimum weight reduced to 2575 lbs from 2650 lbs. · SMX allows OE instrument cluster relocation for aftermarket dash mounting, with wiring re-routed only; alternate gauges now permitted. · T1 GT4 tire sizes adjusted across ten cars: most non-DOT rear to 305/660, Audi and McLaren 305/645, Camaro and Mustang 305/680. · BMW M4 GT4 (G82) added to T1 GT4 at 3525 lbs minimum weight with Red power stick control. · T1 Spec Lines now permits 5.5 inch clutch in Engine Notes. · T1 GT4 Spec Line 4020 restrictor opens from 44mm to 45mm, minimum weight drops to 3400 lbs. · Mustang Darkhorse R added to T1 homologated cars at 3,250 lbs minimum with 305/315 tires, ineligible for Runoffs until 3 Super Tour events. · T1 Corvette may roll or flatten wheel opening lips for tire clearance; plastic fenders may remove lips if edge thickness matches basic material. · T1 E46 M3 S54 can now use Dinan Throttle Body #D760-3400 on 3.250L engine. · T2 and T3 Mustang spec lines remove redundant driveshaft alternate/aluminum allowance wording. · T4 Mini Cooper S R53 now allows Alta 15% Pulley #AMPENG20X. · T4 removes restriction on aftermarket wheel weight minimum of 15 lbs. · T2, T3, T4 fuel cell installations may remove charcoal canisters, emissions valves, and sensors. · Mazda 3 (19-24) newly classified in T4 at 2850 lbs with 17×8 wheels and 245 tires. · T2, T3, T4 brake component wording clarified: 2-piece rotors allowed in T2 within 5% OE diameter, T3 within 2% OEM diameter. · T2, T3, T4 fuel cell cars may remove charcoal canisters, emissions valves, and sensors. · T3 and T4 Mazda RX-8 and MX-5 permit transmission kit #0000-02-5700. · Porsche Spec Boxster moves to T4, minimum weight 2750 lbs, requires 3 Super Tour events before Runoffs eligibility. · Ford Mustang V6 (05-14) newly classified to T4 with 50mm restrictor, 3400 lbs minimum weight. · T4 BMW 320i 14-15 Spec Line expires 12/31/24 removed; Turner Motorsports intercooler #024703TMS02 allowed. · Unable to summarize: rule changes specified in letter #37281, not provided. · Cadillac CTS 02-07 3.6L classified in T3. · T4 Honda Civic Si 06-11 minimum weight drops 50 lbs to 2900, restrictor clarified. · T4 NC MX-5 06-15 removes SM5 suspension allowance, clarifies Mazda Motorsports LSD part number, adds weight penalty for other LSDs. · T4 Mazda MX-5 Miata/Club (16-18) wheel size changes to 17 x 7.5 inches. · T4 Mazda RX-8 gets 59mm restrictor and 3200 lbs; MX-5 Club drops to 2550 lbs. · T4 Mazda MX5 Miata/Club/RF 19-24 wheel size changes to 17 x 7.5. · T4 Honda Civic Si 06-11 permitted to use LSD per category rules. · AS Ford Mustang GT models gain alternate transmission ratio options for 2024-09-01. · SMX Spec MX-5 camera requirement wording changed; non-functioning recorder now grounds for penalty or disqualification. · SMX Spec MX-5 must run latest AIM Data Logger Spec MX-5 ECU Protocol; wording clarification for technical compliance. · SMX Mazda Miata OE versus OEM definitions clarified in GCR Section 9.1.7.1. · SM and SMX shifter bushing rules clarified: alternate bushing at shift lever bottom now allowed. · T4 Chevrolet Camaro V-6 (96-02) weight reduced from 3250 lbs to 3150 lbs. · T4 Mazda MX-5 Miata/Club 16-18 drops 50 lbs to 2650; 19-24 RF drops 50 lbs to 2750. · Ford Mustang GT 5.0L and V6 now permit Track/Performance Package parts in T2 and T3. · Mercedes C300 4Matic 2008-2011 homologated to T4 at 3,725 lbs with 18x8.5 wheels, 245 max tires, 3.27 final drive. · T2-T4 Ford Mustangs: remove 25 lbs penalty for non-OEM driveshaft, clarify alternate driveshaft allowances. · T4 Mini Cooper S (02-04) deleted; (05-06) model year corrected to R53; (07-13) R56 simplified specs; (2014-2023) added with spring rates. · T4 OEM intake chambers, resonators and acoustic devices may be removed if ports sealed and before restrictor. · Audi S4 (2000-2002) moves to T3 with 3400 lbs minimum weight, 38mm turbo inlet restrictor required. · AS Ford Mustang GT 5.0L (2018-) classified at 3600 lbs with 60mm restrictor, Brembo BBK permitted. · T4 Mazda MX-5 Club 06-15 now permits OEM front spoiler NF51-V4-900F. · T4 Ford Mustang V6 (05-10) weight reduced 50 lbs to 3225. · T4 Mini Cooper S 02-04 and 05-06 now allow Milltek exhaust manifold #SSXM459 and 25mm rear sway bar. · AS Chevrolet Camaro 1LE (2016-) classified with 3600 lbs minimum weight, 60mm restrictor, 275 tires. · AS Chevrolet/Pontiac Camaro & Firebird 82-92 5.7L LS1 classified at 3200 lbs with 65mm restrictor plate required. · AS Chevrolet Camaro, Firebird, and Ford Mustang models permitted to use Flo Tek cylinder heads. · Mercedes AMG-C63 S (2023) classified in T1 with 4000 lbs minimum weight and 3700 restrictor. · T3 and T4 Mazda RX-8 may remove or disable factory oil injection system. · T4 Mazda MX5 Miata/Club/RF year range extended to 2024, suspension package permitted with 100 lbs weight increase. · T4 Volkswagen Rabbit 2.5 (06-09) front brakes increase from 228 to 288 vented disc. · T2, T3, T4 driveshafts may use alternative materials or one-piece units; non-OEM adds 25 lbs. · T4 Mazda MX-5 Miata/Club 16-18 removes differential stock requirement, allows up to 500lb front and 300lb rear springs. · AS Camaro/Firebird and GTO LS1 connecting rods approved: Callies CSC6100DS6A2AH, Scat 2-1CR6100-944, GM 12649190. · AS Cadillac CTS-V, Chevrolet Camaro SS, Dodge Challenger, Ford Mustang GT, Pontiac GTO allowed 11" wheels until 3/1/25. · T1 Honda S2000 classified with 2400 lb minimum weight, 2950 cc displacement, 4.75" supercharger pulley. · T4 Mazda RX-8 allows Mazdaspeed radiator, coil spring kit, OE rear spoiler, front air dam, springs to 700 lb front/400 lb rear, oil metering pump bypass, sway bars to 32 mm front/19 mm rear. · Chevrolet Camaro, Pontiac Firebird 70-81 Full Prep classified AS at 3400-3600 lbs with 250 lb weight reduction. · AS class: multiple cars gain fuel cell placement note allowing 24 inches from standard tank, unrestricted filler location. · Chevrolet Camaro 16- Full Prep classified into AS at 3400 lbs with 250 lb weight reduction. · AS adds Ford Mustang GT 05-14 Restricted prep Engine with 62mm FPR, 3400 lbs minimum, 18-inch wheels. · Pontiac GTO 2006-2009 LS1 added to T1 as Spec Line 1590, 5700 cc, 3400 lbs minimum. · T2-T4 Spec Lines remove wheelbase requirement, replace with Required Restrictor specification. · T4 Mazda RX-8 rear spring opens to any 400lb, was specific part numbers only. · T2 and T3 Nissan 370Z brake rotors enlarged: front 320x28 to 355x32mm, rear 320x16 to 350x20mm vented. · C8 Corvette T1 restrictor plate increases from 70mm to 72mm flat plate. · T1 NEW class removes 23 spec lines including Acura NSX, Ferrari, Porsche 996, Nissan Z cars, and others; Porsche 997 spec line 1680 expiration removed. · T2, T3, T4 battery replacement wording simplified; OEM weight tolerance requirement removed. · T4 Mazda MX-5 Miata/Club (16-18) and (19-21) permitted to replace 3rd and 4th gears with specific parts. · T4 now permits C-Spec cars to compete alongside B-Spec cars. · T2-T4 spec lines for 46 cars expire 12/31/24; appeal required to continue. · T1-GT4 batch adjustments: five cars lighter, two heavier, restrictors and ECU maps changed, five models now eligible for Runoffs. · T1 spec lines 1000, 1010, 1020, 1040, 1360, 1400–1410, 1520–1680, 1700–1720 deleted entirely. · T4 Mazda MX-5 ND1 minimum weight increases 50 lbs to 2700; suspension springs now allow up to 500 lb front, 300 lb rear. · T4 BRZ/FRS/86 spring allowance clarified: 225 lb front and 300 lb rear springs permitted; non-OEM LSD allowed with +50 lbs penalty. · T4 Acura TSX 2004-2008 now allows header. · T3 Nissan 370Z model years expanded to include NISMO Edition through 2022. · T1 Chevrolet Corvette C5 LS2 added with 6000cc displacement, 3300 lbs minimum weight, 72mm flat plate restrictor. · T1 Chevrolet Corvette C7 (14-19) including Z51, Grandsport newly classified as homologated car. · T1 Gen 5 Camaro minimum weight drops 75 lbs to 3475; restrictor increases 70mm to 75mm. · T1 Aston Martin Vantage permitted to use OEM Sportshift II transmission. · Pontiac GTO 2006-2009 re-integrated into T1 with LS2 at 3400 lbs, 72mm restrictor, and LS3 at 3500 lbs, 61mm restrictor. · T1 Porsche 997-1 GT3 Cup added at spec line 4210, minimum weight 3050 lbs. · T4 Mercedes Benz CLK 320 Coupe model years expand to 2000-2007, C320 Sedan added. · AS crate motor part number specified: GM Performance CT400 P/N 19370604 engine assembly for GM vehicles. · AS Spec Lines Ford Mustang GT 5.0L (15-17) max wheel size increases to 19.0 inches. · AS Dodge Challenger 5.7L/6.1L/6.4L V8 now permits SPC-66045 alternate front upper control arms. · AS Dodge Challenger 5.7L/6.1L/6.4L V8 allows alternate front brake caliper adapters for updated or backdated components. · Chevrolet Camaro GT4-R classified in T1 GT4 Spec Line 4035, minimum weight 3375 lbs, 315 max tire, 63mm restrictor, ineligible for Runoffs. · T1 Dodge Viper ACR / SRT RT-10 and ACR/ACR-X spec lines 1350 and 1370 remove 12/23 expiration. · T1 GT4 McLaren 570S, Mercedes AMG GT4, and Porsche 718 Cayman GT4 CS MR now eligible for Runoffs competition. · T1 GT4 BMW M4 Spec Line Number changed from 4050 to 4030. · T1 Corvette C5 gains approved aero parts: carbon rear spoiler, vented front splitter, side skirts, with 50 lb weight reduction allowed. · T3 Mazda RX-8 removes transmission/final drive pairing requirement; T4 removes same requirement, adds Mazdaspeed radiator and coil spring kit. · T3 BMW 320i (14-15) gains aftermarket intercooler permission; T4 loses it. · T3 Pontiac Solstice GXP minimum ride height set to 3 inches. · T1 Dodge Viper ACR/ACR-X restrictor increases from 50mm to 60mm flat plate. · T1 Dodge Viper ACR/ACR-X: Spec Line 1370 restrictor increases to 55mm, Line 1390 decreases to 55mm. · T1 Ford Mustang S197 05-14 now requires OEM 8.8 differential housing. · T1 Chevrolet Camaro Gen 5 LS7 gets two spec lines: 1131 with 70mm restrictor, 1136 with 53mm restrictor, both 3450 lbs minimum. · T1 Chevrolet Camaro Gen 5, Corvette C5 and C6: engine resleeve restricted to stock parameters only, no longer LS3 bore/stroke. · T4 Mini Cooper S R53 loses 50 lbs, to 2700 for both 02-04 and 05-06 model years. · T1 Ford Mustang S197 (05-14) reinstated with 3550 lbs minimum weight, 75mm restrictor, Voodoo engine permitted. · T4 Mini Cooper S all years now run 17-inch wheels, up from 16, with wider rims to 8 inches. · T4 Volkswagen Rabbit 2.5 (06-09) consolidates 06-07 and 08-09 models; Integrated Engineering intake allowed with 25lb penalty. · T4 Audi A4 2.8 V6 wheels grow to 17x8, tyres to 245, springs now 800lb with 32mm sway bars. · T1 GT4 weights clarified for nine cars, ranging from 3200 lbs Porsche 718 Cayman to 3575 lbs Aston Martin. · T1-GT4 McLaren 570S and Mercedes AMG GT4 front tires widen to 315 mm. · T1 Chevrolet Camaro Gen5 LS3-6160 adds 70mm flat plate restrictor, weight 3550 lbs. · Acura TSX 2004-2008 newly classified in T4 at 3000 lbs minimum weight with 2354cc engine. · T4 Mustang rear sway bar increases from 22mm to 28mm permitted. · T1 cars with aftermarket sequential transmissions get 10-inch max bellhousing; non-sequential cars gain 100 lbs weight break. · T1 GT4 all nine cars lose 125 lbs minimum weight with driver, from 3200–3575 to 3075–3450. · T1 removes GCR Section 9.1.9.1.A. and T1 Spec Lines entirely, sunsetting pre-2023 Touring 1 rules. · T3 BMW 320I now permitted to use aftermarket intercooler.showhide
T1 T1 Parity Compared to GT4 #37170weight +125 lbsslowerT1 Mustang gains 125 lbs to 3600, restrictor shrinks 65mm to 60mm. Corvette gains 50 lbs to 3500, restrictor shrinks 70mm to 67mm. BMW deleted.
T1 Clarification of Request Approval #37273 #37399engineunclearT1 E46 M3 Spec Line 1050 allows VAC Motorsports throttle body VAC-TB-S54 on 3.250L engine instead of Dinan.
T1 C8 Corvette Facts #37400weight -100 lbsfasterT1 Chevrolet Corvette C8 (2023-23) minimum weight reduced from 3600 lbs to 3500 lbs.
T1 Camaro Gen 5 Competitive Disadvantage #37440inductionfasterT1 Chevrolet Camaro Gen 5 restrictor increases from 75mm to 80mm flat plate.
T1 Tire Changes in the Rules for GT4 #37497tyres & wheelsunclearT1 Audi R8 GT4 Spec Line #4020 maximum tyre size changes to 315 DOT, 305/645, or 30/65-18 (f), 33/68-18 (r) Non-DOT.
T4 Ford Mustang V6 (05-14) #37516wordingwordingT4 Ford Mustang V6 (05-14) final drive set to 3.45, GT/CS front bumper cover permitted with front fascia.
T4 Request to Classify Club Spec in Appropriate Touring Classes #37523cars addedcars addedFord SCCA Club Spec Mustang classified T3 at 3350 lbs with driver; Mazda SCCA Club Spec MX-5 classified T4 at 2500 lbs with driver.
AS Increase Coyote Engine Restrictor to 80mm #36177inductionfasterAS Ford Mustang Coyote engines increase restrictor to 80mm from 64mm or 67mm.
AS Performance Pack for 2015+ Mustang #36867enginefasterAS Mustang GT 05-14 4.6L loses 300 lbs; 15-17 and 2018+ models lose 61mm and 60mm restrictors respectively.
AS Gear Ratios #37131wordingwordingAS class gear ratio options specified for multiple American muscle cars, including Cadillac CTS-V, Chevrolet Camaro, Ford Mustang, Dodge Challenger, and Pontiac GTO.
AS ECU specs for LS engine #37208enginefasterAS LS-engine cars gain ECU freedom; Camaro/Firebird 93-02 LS1 removes fuel cell location restriction.
T4 Remove spec lines that have expired #37269removedremovedT2, T3, T4 remove nine, nine, and thirty-six expired spec lines respectively, effective 2025-01-01.
SM E&O SMX Regs 9.1.7.1.D.5.u-.w #37070wordingwordingSMX allows OE instrument cluster relocation for aftermarket dash mounting, with wiring re-routed only; alternate gauges now permitted.
T1 Changes to T1 Tires for GT4 and Other Cars #35383tyres & wheelsunclearT1 GT4 tire sizes adjusted across ten cars: most non-DOT rear to 305/660, Audi and McLaren 305/645, Camaro and Mustang 305/680.
T1 G82 M4 GT4 inclusion in T1 #35864cars addedcars addedBMW M4 GT4 (G82) added to T1 GT4 at 3525 lbs minimum weight with Red power stick control.
T1 Alt. Clutch Allowance #36606wordingwordingT1 Spec Lines now permits 5.5 inch clutch in Engine Notes.
T1 BOP Changes Need Updates #36667weight -150 lbsfasterT1 GT4 Spec Line 4020 restrictor opens from 44mm to 45mm, minimum weight drops to 3400 lbs.
T1 Request Ford Performance Darkhorse R in T1 #37136cars addedcars addedMustang Darkhorse R added to T1 homologated cars at 3,250 lbs minimum with 305/315 tires, ineligible for Runoffs until 3 Super Tour events.
T1 Car Mods for T1 Corvette under line item 1150 #37173wordingwordingT1 Corvette may roll or flatten wheel opening lips for tire clearance; plastic fenders may remove lips if edge thickness matches basic material.
T1 Increased Bore Throttle Bodies for E46 M3 S54 Engine #37273enginefasterT1 E46 M3 S54 can now use Dinan Throttle Body #D760-3400 on 3.250L engine.
T4 Redundant Verbiage Regarding Mustang Spec Lines for Driveshaft #36484wordingwordingT2 and T3 Mustang spec lines remove redundant driveshaft alternate/aluminum allowance wording.
T4 R53 Mini Cooper S Weight Reduction Request #36612enginefasterT4 Mini Cooper S R53 now allows Alta 15% Pulley #AMPENG20X.
T4 Allowable Wheel Offset #36855wordingwordingT4 removes restriction on aftermarket wheel weight minimum of 15 lbs.
T4 Fuel Emissions Components #37076wordingwordingT2, T3, T4 fuel cell installations may remove charcoal canisters, emissions valves, and sensors.
T4 2019-2024 Mazda 3 for T4 #37077cars addedcars addedMazda 3 (19-24) newly classified in T4 at 2850 lbs with 17×8 wheels and 245 tires.
T4 fix brake wording #37129wordingwordingT2, T3, T4 brake component wording clarified: 2-piece rotors allowed in T2 within 5% OE diameter, T3 within 2% OEM diameter.
T4 Evaporative emissions systems #37130wordingwordingT2, T3, T4 fuel cell cars may remove charcoal canisters, emissions valves, and sensors.
T4 Allow Spec MX5 upgrade kit for 2009-11 RX8 S2 Transmision #37140wordingwordingT3 and T4 Mazda RX-8 and MX-5 permit transmission kit #0000-02-5700.
T4 Move Spec Boxster to T4 #37158cars addedcars addedPorsche Spec Boxster moves to T4, minimum weight 2750 lbs, requires 3 Super Tour events before Runoffs eligibility.
T4 3.7 Mustangs to T4 #37188cars addedcars addedFord Mustang V6 (05-14) newly classified to T4 with 50mm restrictor, 3400 lbs minimum weight.
T4 BMW 320i Spec Line #37204wordingwordingT4 BMW 320i 14-15 Spec Line expires 12/31/24 removed; Turner Motorsports intercooler #024703TMS02 allowed.
T4 MX5 2006-2015 NC Help #37221otherunclearUnable to summarize: rule changes specified in letter #37281, not provided.
T4 Classification for a 2005 Cadillac CTS 3.6 liter 6 speed manual #37224cars addedcars addedCadillac CTS 02-07 3.6L classified in T3.
T4 Civic SI in T4 #37248weight -50 lbsfasterT4 Honda Civic Si 06-11 minimum weight drops 50 lbs to 2900, restrictor clarified.
T4 2006-2015 T4 NC Mx5 spec line #37278wordingwordingT4 NC MX-5 06-15 removes SM5 suspension allowance, clarifies Mazda Motorsports LSD part number, adds weight penalty for other LSDs.
T4 ND MX-5 wheel allowance #37279tyres & wheelsunclearT4 Mazda MX-5 Miata/Club (16-18) wheel size changes to 17 x 7.5 inches.
T4 T4 BOP #37281weight +75 lbsslowerT4 Mazda RX-8 gets 59mm restrictor and 3200 lbs; MX-5 Club drops to 2550 lbs.
T4 Allow 7.5 #37286tyres & wheelstyres & wheelsT4 Mazda MX5 Miata/Club/RF 19-24 wheel size changes to 17 x 7.5.
T4 Bop Request 06-11 Honda Civic Si #37013wordingwordingT4 Honda Civic Si 06-11 permitted to use LSD per category rules.
AS Mustang transmission ratios #36662wordingunclearAS Ford Mustang GT models gain alternate transmission ratio options for 2024-09-01.
SM SMX Camera Rule Correction #36496wordingwordingSMX Spec MX-5 camera requirement wording changed; non-functioning recorder now grounds for penalty or disqualification.
SM Committee) AIM ECU Protocol #36556wordingwordingSMX Spec MX-5 must run latest AIM Data Logger Spec MX-5 ECU Protocol; wording clarification for technical compliance.
SM Committee) OE versus OEM Definitons #36608wordingwordingSMX Mazda Miata OE versus OEM definitions clarified in GCR Section 9.1.7.1.
SM Committee) Shifter Bushing #36611wordingwordingSM and SMX shifter bushing rules clarified: alternate bushing at shift lever bottom now allowed.
T4 T4 Camaro V6 weight reduction #36232weightfasterT4 Chevrolet Camaro V-6 (96-02) weight reduced from 3250 lbs to 3150 lbs.
T4 BOP adjustment for ND MX5s #36345weight -50 lbsfasterT4 Mazda MX-5 Miata/Club 16-18 drops 50 lbs to 2650; 19-24 RF drops 50 lbs to 2750.
T4 Mustang T2/T3 #35877wordingunclearFord Mustang GT 5.0L and V6 now permit Track/Performance Package parts in T2 and T3.
T4 Homologation of car to T4 #36030cars addedcars addedMercedes C300 4Matic 2008-2011 homologated to T4 at 3,725 lbs with 18x8.5 wheels, 245 max tires, 3.27 final drive.
T4 T2-T4 Driveshaft Mistake...? #36050weightfasterT2-T4 Ford Mustangs: remove 25 lbs penalty for non-OEM driveshaft, clarify alternate driveshaft allowances.
T4 MINI Cooper S Spec Lines Corrections. #36086wordingwordingT4 Mini Cooper S (02-04) deleted; (05-06) model year corrected to R53; (07-13) R56 simplified specs; (2014-2023) added with spring rates.
T4 Allow Removal of Sound Tubes #36130inductionfasterT4 OEM intake chambers, resonators and acoustic devices may be removed if ports sealed and before restrictor.
T4 B8/8.5 Audi S4 T3 and T2 #36195cars addedcars addedAudi S4 (2000-2002) moves to T3 with 3400 lbs minimum weight, 38mm turbo inlet restrictor required.
AS Request for Classification of 2018-2023 mustang In #35764cars addedcars addedAS Ford Mustang GT 5.0L (2018-) classified at 3600 lbs with 60mm restrictor, Brembo BBK permitted.
T4 Allow OEM Front Spoiler 06-08 Miata in T4 #35941aerofasterT4 Mazda MX-5 Club 06-15 now permits OEM front spoiler NF51-V4-900F.
T4 T4 Mustang Weight Reduction In T4 Spec #36051weight -50 lbsfasterT4 Ford Mustang V6 (05-10) weight reduced 50 lbs to 3225.
T4 R53 Mini Cooper S spec line request In #36056otherfasterT4 Mini Cooper S 02-04 and 05-06 now allow Milltek exhaust manifold #SSXM459 and 25mm rear sway bar.
AS 6th gen Camaro limited prep #35733cars addedcars addedAS Chevrolet Camaro 1LE (2016-) classified with 3600 lbs minimum weight, 60mm restrictor, 275 tires.
AS Chevrolet/Pontiac Camaro & Firebird (82-92) 5.7L V8 LS1 Alum BLK #35825cars addedcars addedAS Chevrolet/Pontiac Camaro & Firebird 82-92 5.7L LS1 classified at 3200 lbs with 65mm restrictor plate required.
AS Full Prep Head #35891otherotherAS Chevrolet Camaro, Firebird, and Ford Mustang models permitted to use Flo Tek cylinder heads.
T1 Please Expedite classing the C63 Mercedes #35987cars addedcars addedMercedes AMG-C63 S (2023) classified in T1 with 4000 lbs minimum weight and 3700 restrictor.
T4 Allow T4 and T3 RX8 to Disable/Remove Factory Oil Inj. #35761engineunclearT3 and T4 Mazda RX-8 may remove or disable factory oil injection system.
T4 2023 ND2 Miata Classification and Allowances #35837weightslowerT4 Mazda MX5 Miata/Club/RF year range extended to 2024, suspension package permitted with 100 lbs weight increase.
T4 Errors and Omissions for 06-09 VW Rabbit Rotor #35851suspension & brakesfasterT4 Volkswagen Rabbit 2.5 (06-09) front brakes increase from 228 to 288 vented disc.
T4 Driveshafts #35916weightslowerT2, T3, T4 driveshafts may use alternative materials or one-piece units; non-OEM adds 25 lbs.
T4 GCR ERROR - letter not properly applied to GCR #35999suspension & brakesfasterT4 Mazda MX-5 Miata/Club 16-18 removes differential stock requirement, allows up to 500lb front and 300lb rear springs.
AS Restricted Prep Aftermarket Parts Request #35682wordingwordingAS Camaro/Firebird and GTO LS1 connecting rods approved: Callies CSC6100DS6A2AH, Scat 2-1CR6100-944, GM 12649190.
AS Allowance of 11 #35824tyres & wheelsfasterAS Cadillac CTS-V, Chevrolet Camaro SS, Dodge Challenger, Ford Mustang GT, Pontiac GTO allowed 11" wheels until 3/1/25.
T1 Honda S2000 #35582cars addedcars addedT1 Honda S2000 classified with 2400 lb minimum weight, 2950 cc displacement, 4.75" supercharger pulley.
T4 Corrections to T4 RX8 Spec line #35767wordingwordingT4 Mazda RX-8 allows Mazdaspeed radiator, coil spring kit, OE rear spoiler, front air dam, springs to 700 lb front/400 lb rear, oil metering pump bypass, sway bars to 32 mm front/19 mm rear.
AS Request to Classify 1970-1981 Camaro and Firebird in AS #33659cars addedcars addedChevrolet Camaro, Pontiac Firebird 70-81 Full Prep classified AS at 3400-3600 lbs with 250 lb weight reduction.
AS Fuel Cell 12 #34194wordingwordingAS class: multiple cars gain fuel cell placement note allowing 24 inches from standard tank, unrestricted filler location.
AS Please Classify the 6th Gen Into AS. #35448cars addedcars addedChevrolet Camaro 16- Full Prep classified into AS at 3400 lbs with 250 lb weight reduction.
AS spec lines #35713cars addedcars addedAS adds Ford Mustang GT 05-14 Restricted prep Engine with 62mm FPR, 3400 lbs minimum, 18-inch wheels.
T1 9.1.9.1 T1 new category item/ line 26 rule to expire Jan 1 2023 #35411cars addedcars addedPontiac GTO 2006-2009 LS1 added to T1 as Spec Line 1590, 5700 cc, 3400 lbs minimum.
T4 Allow any 400lb rear spring in the RX8 #35433suspension & brakessuspension & brakesT4 Mazda RX-8 rear spring opens to any 400lb, was specific part numbers only.
T4 370Z Brake Rotor Size Correction #35487suspension & brakessuspension & brakesT2 and T3 Nissan 370Z brake rotors enlarged: front 320x28 to 355x32mm, rear 320x16 to 350x20mm vented.
T1 C8 Corvette T1 Restrictor Plate Request #35213inductionfasterC8 Corvette T1 restrictor plate increases from 70mm to 72mm flat plate.
T1 The Cars Have Expired #35379removedremovedT1 NEW class removes 23 spec lines including Acura NSX, Ferrari, Porsche 996, Nissan Z cars, and others; Porsche 997 spec line 1680 expiration removed.
T4 More Car Lightening Stuff #35319weightfasterT2, T3, T4 battery replacement wording simplified; OEM weight tolerance requirement removed.
T4 ND Missed Items #35352wordingwordingT4 Mazda MX-5 Miata/Club (16-18) and (19-21) permitted to replace 3rd and 4th gears with specific parts.
T4 Inclusion of B-C spec cars in T4 #35374cars addedcars addedT4 now permits C-Spec cars to compete alongside B-Spec cars.
T4 T2-T4 Set expiration dates on spec lines #35378wordingwordingT2-T4 spec lines for 46 cars expire 12/31/24; appeal required to continue.
T1 GT4 batch adjustment in T1 #35162other -85 lbsunclearT1-GT4 batch adjustments: five cars lighter, two heavier, restrictors and ECU maps changed, five models now eligible for Runoffs.
T4 Mazda MX-5 ND1 Spec Line Request #34232weight +50 lbsslowerT4 Mazda MX-5 ND1 minimum weight increases 50 lbs to 2700; suspension springs now allow up to 500 lb front, 300 lb rear.
T4 BRZ/FRS/86 Spring Allowance #35038wordingwordingT4 BRZ/FRS/86 spring allowance clarified: 225 lb front and 300 lb rear springs permitted; non-OEM LSD allowed with +50 lbs penalty.
T4 TSX Allowance #35219aerofasterT4 Acura TSX 2004-2008 now allows header.
T4 Requested Update of Model Years of 370Z #35231wordingwordingT3 Nissan 370Z model years expanded to include NISMO Edition through 2022.
T1 New T1 add spec line for C5 corvette LS2 engines (Copy from C6) #33764cars addedcars addedT1 Chevrolet Corvette C5 LS2 added with 6000cc displacement, 3300 lbs minimum weight, 72mm flat plate restrictor.
T1 C7 Corvette Rule Change Request #34897cars addedcars addedT1 Chevrolet Corvette C7 (14-19) including Z51, Grandsport newly classified as homologated car.
T1 Camaro Gen 5 Weight Reduction Due to Competitive Disadvantage #35092weight -75 lbsfasterT1 Gen 5 Camaro minimum weight drops 75 lbs to 3475; restrictor increases 70mm to 75mm.
T1 Addendum to Letter #35022: Drivetrain Rule #35105wordingwordingT1 Aston Martin Vantage permitted to use OEM Sportshift II transmission.
T1 2004 - 2006 Pontiac GTO Re-Integration Back Into T1 #34403cars addedcars addedPontiac GTO 2006-2009 re-integrated into T1 with LS2 at 3400 lbs, 72mm restrictor, and LS3 at 3500 lbs, 61mm restrictor.
T1 Request to Classify Porsche 997-1 GT3 Cup #34561cars addedcars addedT1 Porsche 997-1 GT3 Cup added at spec line 4210, minimum weight 3050 lbs.
T4 Inclusion of similar car. (CLK 320) #34626cars addedcars addedT4 Mercedes Benz CLK 320 Coupe model years expand to 2000-2007, C320 Sedan added.
AS Crate Motor Part Numbers #32944wordingwordingAS crate motor part number specified: GM Performance CT400 P/N 19370604 engine assembly for GM vehicles.
AS Request wheel size change #33007tyres & wheelsfasterAS Spec Lines Ford Mustang GT 5.0L (15-17) max wheel size increases to 19.0 inches.
AS Alternative Upper Front Control Arms for Dodge Challenger #33352wordingwordingAS Dodge Challenger 5.7L/6.1L/6.4L V8 now permits SPC-66045 alternate front upper control arms.
AS Front Brake Caliper Adapters for Dodge Challenger #33353wordingwordingAS Dodge Challenger 5.7L/6.1L/6.4L V8 allows alternate front brake caliper adapters for updated or backdated components.
T1 Why no Camaro? #34421cars addedcars addedChevrolet Camaro GT4-R classified in T1 GT4 Spec Line 4035, minimum weight 3375 lbs, 315 max tire, 63mm restrictor, ineligible for Runoffs.
T1 Request to Remove Expiration from T1 spec lines #1350 & #1370 #34470wordingwordingT1 Dodge Viper ACR / SRT RT-10 and ACR/ACR-X spec lines 1350 and 1370 remove 12/23 expiration.
T1 Remove #34475wordingwordingT1 GT4 McLaren 570S, Mercedes AMG GT4, and Porsche 718 Cayman GT4 CS MR now eligible for Runoffs competition.
T1 Error in T1 GT4 numbering scheme- #34578wordingwordingT1 GT4 BMW M4 Spec Line Number changed from 4050 to 4030.
T1 C5 Approved Aero That Was Mistakenly Deleted #34374aerofasterT1 Corvette C5 gains approved aero parts: carbon rear spoiler, vented front splitter, side skirts, with 50 lb weight reduction allowed.
T4 Rules Clarification for Mazda RX8 Spec Line #34395wordingwordingT3 Mazda RX-8 removes transmission/final drive pairing requirement; T4 removes same requirement, adds Mazdaspeed radiator and coil spring kit.
T4 rule book corrections #34437otherfasterT3 BMW 320i (14-15) gains aftermarket intercooler permission; T4 loses it.
T4 Ride Height Correction for the T3 Solstice. #34615wordingwordingT3 Pontiac Solstice GXP minimum ride height set to 3 inches.
T1 Viper Cleanup #34107inductionfasterT1 Dodge Viper ACR/ACR-X restrictor increases from 50mm to 60mm flat plate.
T1 Viper 8300 OEM FPR Size #34268inductionunclearT1 Dodge Viper ACR/ACR-X: Spec Line 1370 restrictor increases to 55mm, Line 1390 decreases to 55mm.
T1 Ford Mustang S197 (05-14) Clarification #34450wordingwordingT1 Ford Mustang S197 05-14 now requires OEM 8.8 differential housing.
T1 Gen 5 Camaro Engine #33875cars addedcars addedT1 Chevrolet Camaro Gen 5 LS7 gets two spec lines: 1131 with 70mm restrictor, 1136 with 53mm restrictor, both 3450 lbs minimum.
T1 Inquiry to letter #33682 #34071engineslowerT1 Chevrolet Camaro Gen 5, Corvette C5 and C6: engine resleeve restricted to stock parameters only, no longer LS3 bore/stroke.
T4 2002-2006 Mini Cooper S R53 Spec Line Request #34336weight -50 lbsfasterT4 Mini Cooper S R53 loses 50 lbs, to 2700 for both 02-04 and 05-06 model years.
T1 Request to reinstate T1 S197 Mustang #34048cars addedcars addedT1 Ford Mustang S197 (05-14) reinstated with 3550 lbs minimum weight, 75mm restrictor, Voodoo engine permitted.
T4 05-06 Mini Wheel Weight #34112tyres & wheelsfasterT4 Mini Cooper S all years now run 17-inch wheels, up from 16, with wider rims to 8 inches.
T4 96-01 Audi a4 2.8 Spring Rate #34217suspension & brakesfasterT4 Audi A4 2.8 V6 wheels grow to 17x8, tyres to 245, springs now 800lb with 32mm sway bars.
T1 T1 GT4 adjustments #33786wordingwordingT1 GT4 weights clarified for nine cars, ranging from 3200 lbs Porsche 718 Cayman to 3575 lbs Aston Martin.
T1 Touring 1 Tire Sizes #34191tyres & wheelsfasterT1-GT4 McLaren 570S and Mercedes AMG GT4 front tires widen to 315 mm.
T1 Clarification for Camaro Gen5 2010-2015 #33739inductionslowerT1 Chevrolet Camaro Gen5 LS3-6160 adds 70mm flat plate restrictor, weight 3550 lbs.
T4 Request to Classify 2004-2008 Acura TSX in T4 #33590cars addedcars addedAcura TSX 2004-2008 newly classified in T4 at 3000 lbs minimum weight with 2354cc engine.
T4 T4 Mustang Brakes/Swaybar #34036suspension & brakesfasterT4 Mustang rear sway bar increases from 22mm to 28mm permitted.
T1 Sequential Gearbox Limitations in T1 #33691wordingwordingT1 cars with aftermarket sequential transmissions get 10-inch max bellhousing; non-sequential cars gain 100 lbs weight break.
T1 T1 GT4 adjustments #33786weightfasterT1 GT4 all nine cars lose 125 lbs minimum weight with driver, from 3200–3575 to 3075–3450.
T1 Sunset of pre 2023 Touring 1 Rules. #33916wordingwordingT1 removes GCR Section 9.1.9.1.A. and T1 Spec Lines entirely, sunsetting pre-2023 Touring 1 rules.
T4 BMW 320I intercooler #33762otherfasterT3 BMW 320I now permitted to use aftermarket intercooler.
Cal Club 2023 CALCL232023-02-24
213 earlier rule changes on record, in force before Cal Club 2023 (from 2019)38 weight · 34 cars added · 23 suspension & brakes · 13 tyres & wheels · 8 engine · 8 induction · 7 aero · 77 wording · 5 other · GT4 McLaren 570S maximum tire size changes to 285 front, 315 rear. · T4 Mazda MX-5 ND2 (19-21) classified: 1998cc, 2309mm wheelbase, 225 max tires, 2800 lbs. · T2/T3 Mustang GT 5.0L and V6 (11-14) may remove upper grille fog lights, replace with mesh or screen. · T4 Mazda MX-5 Club Model 06-15 Mazda Motorsports LSD part number corrected from 32655 to 0000-02-5564. · SM Mazda MX-5 Miata 01-05 weight increases to 2450 lbs, or 2465 with alternate bore. · Eight GT4 models added to T1 with weights from 3200 to 3575 lbs and restricted power per SRO 2022 rules. · T4 Honda Civic Si 06-11 now permits 32mm sway bars front and rear and 700 pound springs. · T5 class added as regional-only; T5 tyres maximum width 225, minimum aspect ratio 45. · T2-T5 Touring front and rear suspension maximum negative camber changed to 3.5 degrees. · T4 Ford Mustang V6 (05-10) wheels widen to 18x9, front brakes grow to 314mm vented, weight drops to 3275 lbs. · T4 Mazda MX-5 Club (06-15) minimum weight drops 25 lbs to 2600; Mazda LSD #32655 now permitted without penalty. · T3 Subaru BRZ 2022- minimum weight up to 2975 lbs; spring rate to 1000 F/R, brake parts allowed without penalty. · AS allows Hoosier W2 tyre option in addition to R7, R6, WET/H20. · AS Dodge Challenger 08-20 adds two transmission ratio options: 2.97, 2.10, 1.45, 1.00, 0.74, 0.50 or 2.26, 1.58, 1.19, 1.00, 0.77, 0.63. · T1 Cadillac CTS/CTS-V, Chevrolet Camaro, Pontiac Firebird, Pontiac GTO 6162 OEM minimum weight reduced to 3475 lbs. · T4 Mazda3 04-09 now permits Corksport balance shaft delete kit GEN-6-504-10. · AS Cadillac CTS-V 6.0L V8 removes 50 lbs weight penalty for 295 tire size. · T1-LP Ford Mustang FP350S restrictor increases from 70mm to 75mm. · Mercedes Benz AMG GT4 2017-2021 classified T1 Maximum at 3400 lbs minimum weight with HP-controlled SRO Power Level 2 engine. · T4 Hyundai Tiburon V-6 wheel width increases from 7 to 8 inches at 17-inch diameter. · T4 Mazda3 i 2.0L added as spec line with 1999cc displacement and 2425 lbs minimum weight. · T2-T4 Touring cars with alternative springs may use performance top hats with spherical bearings on shocks and struts. · SM Majors must run authorized Penske shock and mount; Regional competitors' requirement eligibility clarified. · T1 Dodge Viper ACR displacement rises to 8400 OEM, minimum weight drops to 3550 lbs. · T1 Limited T1 wording changed to clarify all T1 cars permitted specifications. · T1 Mazda RX-7 classified: 2700 lbs minimum weight, 44mm restrictor, 13B Rotary with single Garrett Turbo #3076. · T2-T4 cars model year 2018+ may use non-OEM ECU with 75 lb weight penalty via spec line adjustment. · T4 Nissan Sentra SE-R Spec V 02-06 now permits balance shaft removal kit OQR25-NOBAL. · T4 BMW 323 (98-00) wheelbase increases to 2725 mm, final drive ratio changes to 3.07. · T4 Mazda RX-8 04-12 gains Eibach spring alternatives to Mazda Motorsports springs front and rear. · T4 Mazda3 04-09 tire size increases from 235 to 245. · T4 Ford Mustang V6 05-10 shock part numbers corrected to 8741-1494SPORT front and 8241-1240SPORT rear. · T4 Scion FR-S and Subaru BRZ Solo Spec Coupes updated to 2020 specifications Rev 7/20. · T4 2016–18 Mazda MX-5 Miata/Club gains 100 lbs. for approved suspension package with specific springs. · T1 Cadillac CTS/CTS-V, Chevrolet Camaro, Pontiac Firebird, Pontiac GTO LS3 minimum weight reduced to 3475 lbs. · T1 Camaro maximum displacement 7011 loses 50 lbs, to 3500. · T1 removes 33mm brake rotor thickness limit; rotors now unrestricted on thickness. · T2-T4 grill openings may remove non-metallic webbed false sections; 16 square inch limit removed. · T3 Spec Lines Subaru BRZ TS (13-21) added to class specification wording. · T4 Mazda MX-5 Club 06-15 allows non-OEM LSD with +50 lbs penalty; removes stock transmission and differential requirements. · T4 2005-2010 Ford Mustang V6 now specifies Koni damper part numbers 8741.1494 front and 8741.1240 rear. · SMG long tube headers: Borla PN 17237 discontinued, Kooks PN 11312000 and American Racing PN MT3-05134300LSNC approved alternatives. · AS Mercury Capri (79-86) removed as individual spec line, merged into Ford Mustang (79-93) spec line. · AS Spec Mustang SMG loses 3.73 gear ratio and 355/300 mm brake specification. · AS Chevrolet, Pontiac, Ford full prep engines now permit alternate cylinder heads with restrictor plate ALL26180 and 1.250 inserts ALL26186 for regional competition. · T2-T4 clarified: grill opening area may increase max 16 sq in for radiator cooling only, retaining factory mesh shape. · T4 BMW 323 98-00 minimum weight drops to 3250 lbs, 50mm restrictor removed. · T4 Honda Civic Si consolidates 12-13 and 14-15 into single 12-15 spec line with updated suspension allowances. · T2, T3, T4 radiator and coolant hoses may be replaced with aftermarket options; coolant temp sensor modification permitted. · T2, T3, T4 clarify that spec lines listing permitted or allowed parts are alternatives to category rules, not replacements. · T4 Acura RSX/RSX Type-S 02-06 removes requirement that original wheels must remain stock. · T4 Chevrolet Camaro V-6 (96-02) removes requirement that shock/struts, mounts, and transmission differential remain stock. · T1 Mazda MX-5 Miata MazdaSpeed minimum weight rises to 2550 lbs, restrictor increases to 42mm. · T1 Chevrolet Corvette Cadillac XLR classified for model years through 2019. · Nissan Sentra SE-R Spec V (2007–2012) newly classified in T4 at 3000 lbs minimum weight. · T4 Mazda RX-8 04-12 allows alternate sway bars max 32mm front, 19mm rear; removes 60mm restrictor requirement. · T4 BMW 320i (14-15) now allows GFB T9357 aluminum diverter valve. · T4 Honda Civic FWD gets wider 8-inch wheels, 245 tyres max, and sway bar allowances to 29mm front, 22mm rear. · T4 multiple cars: Volkswagen Rabbit 2.5 (08-09) to 2675 lbs; Mazda MX-5/Club (06-15) to 2625 lbs; RX-8 to 3125 lbs; Honda/Acura/Chevy/Mazda wheel widths 7 to 8 inches. · T4 Volkswagen Passat, Jetta 1.8T adds 2014 model year to eligible years. · AS Chevrolet/Pontiac Camaro & Firebird 93-02 now allow BMR AA004 or UMI 2310 adjustable front upper control arms. · AS Pontiac GTO 04-06 LS1 to 3300 lbs, LS2 to 3350 lbs on 295 tire. · T1 BMW E46/E36/Z3 minimum weight increases to 2700 lbs, 3.4L engine car to 2750 lbs. · T1 Dodge Viper SRT-10 restrictor increases from 45mm to 57mm. · T1 Chevrolet Corvette Cadillac XLR LS6 engine now permits Casting #799 heads with no other head modifications. · T4 BMW 320i 14-15 part number corrected from 20121.140 to E10-20-031-01-22. · AS Cadillac CTS-V 6.0L V8 removes 50 lbs tire size penalty, making it lighter. · AS consolidates seven SN95 Mustang spec lines into three: 94-04 including Cobra, 94-95 5.0/5.8, and 96-04 4.6L two/four valve. · AS Camaro/Firebird LT1/LS1 transmission code changes to 6362; Mustang GT 4.6L/5spd changes to 5.0L/6spd with 300 lbs weight reduction. · AS Camaro/Firebird and Mustang GT gear ratio specifications restored with alternate sets permitted. · AS Chevrolet Camaro & Firebird, Ford Mustang variants, Mercury Capri minimum weights increase 50 lbs across all model years. · T1 Ford Mustang Shelby/GT350/GT500 5.0L Coyote restrictor opens from 65mm to 70mm flat plate. · T1 Dodge Viper SRT-10 restrictor increases from 45mm to 57mm. · T1-LP Chevrolet Corvette C7 restrictor increases from 70 to 73 mm. · T1-LP Corvette Z06 06-13 now allows aluminum chassis replacement with equivalent OE steel chassis. · T3 Honda Civic Type-R 2020+ allows brake rotor 45251-TGH-A01 with 25 lb penalty. · T1 Chevrolet Camaro with 6162 displacement minimum weight reduced to 3500 lbs. · T1-LP Chevrolet Corvettes C5 Z06, C6 Grand Sport, and Z06 dry sump kit notes clarified to remove contradictions. · T4 Mini Cooper S (02-04, 05-06) suspension/wheel rules simplified; (07-13) gear ratios changed to 3.31, 2.13, 1.48, 1.14, 0.95, 0.82, final drive to 3.65, brakes to 280 mm. · T4 Ford Mustang V6 05-10 now allows cold air intake. · SM adds procedures for testing obsolete part replacements and BOP updates in sanctioned events with CRB approval. · T2-T4 clutch disc and pressure plate must be at least 95% of factory OEM weight. · AS Mustang 4.6L/5spd loses 300 lbs; 5.0L/6spd gains 56mm restrictor requirement. · AS CTS-V LS6 and LS2 may now use Driveshaft Shop carbon fiber driveshaft for durability. · AS Chevrolet Camaro SS V8 6.2L model years extended from 10-13 to 10-15. · T1 LP removes 50 lbs weight allowance for stock headers, adds aero device allowance up to 100 lbs, permits headers. · T4 Ford Mustang V6 05-10 wheels increase from 17 to 18 inches. · T1 Ford Mustang Challenge 3-valve maximum displacement changes to 4600/5000. · T1 BMW E46 now allows carbon or fiberglass OEM-style dashboards with 25 pound penalty. · T1 Ford Mustang/Thunderbird limited to Shelby/Shelby GT350/GT500 models through 2018. · Dodge Viper ACR classified in T1 with 8400cc displacement, 3600 lbs minimum weight, 55mm restrictor. · BMW M2CS Club Sport classified in T1-LP Spec Lines effective 2021-02-01. · Porsche 997.1 GT3 Cup (2006-2011) classified in T1 at 3600cc, 3150 lbs minimum weight. · Toyota Supra 2020- newly classified in T2 at 3450 lbs minimum weight with 295 tire and 19-inch wheels. · T4 Mazda MX-5 durability rule now applies to T2-T4 instead of T2-T3 only. · T4 Chevrolet Sonic (2011-) spec clarified: 28mm TIR restrictor placement, PCV plug requirement, and allowed suspension parts listed. · T4 Mazda MX-5 06-15 removes front and rear end links from suspension package spec. · T4 BMW Z4 2.5L (03-05) minimum weight reduced from 3100 to 3050 lbs. · T4 2016+ Mazda MX-5 Miata gains allowance for 29mm front and 16mm rear sway bars. · T4 Scion FR-S, Subaru BRZ, and Toyota 86 replace Eibach part 4.10582.880 with 82105.320, 4.10582 and SPC 67660. · T4 Ford Mustang V6 05-10 allows GT 8.8 rear axle with 3.45 or 3.55 ratio at +25 lb penalty. · Ford Mustang GT 5.0L 15-17 Restricted Preparation classified in AS with 55mm flat plate restrictor required. · AS underhood bracing on stock hoods, trunks, and rear decks may be modified or removed. · AS Cadillac CTS-V 04-07 with 295 tire drops to 3450 lbs; Camaro SS V8 10-13 275 tire removed; Challenger 08-20 gains 315 tire option at 3600 lbs. · AS Camaro & Firebird (93-02) and Mustang GT (05-14) specifications restored with 200 lb weight reduction for permitted heads. · T1 Chevrolet Corvette Z06 years extended from 06-12 to 06-13. · BMW M2 CS Cup 2020+ classified in T2 at 3625 lbs with 2979cc engine, 10.5x18 wheels, 295 tires. · T3 and T4 Mazda MX-5 06-15 now allow Mazda Transmission kit part # 0000-02-5700. · T4 Ford Mustang V6 05-10 allows GT 8.8 rear axle with 3.55 final drive, adds 25 lb penalty. · T3 and T4 FR-S, 86, and BRZ year ranges capped: T3 at 2021, T4 at 2017-2021. · AS Dodge Challenger 08-20 gains 6.1L and 6.4L V8 options; 5.7L weight rises to 3500 lbs on 295 tyres, 3600 on 315 tyres. · AS Camaro/Firebird (93-02) and Mustang Coupe GT (05-14) consolidated into single specs with 100 lb and 300 lb weight reductions respectively. · T1 Corvette C8 Z51 gets wider wheels and tyres, weight drops 100 lbs to 3550. · T3 Alfa Romeo 4C Launch Edition now allowed in Spec Lines. · SM aftermarket radiators must mount in original location, maintain core plane, require no body modifications, block openings, keep one OEM fan in stock location; 1990-1997 cars may install upper radiator seal NA75-50-OK7A. · AS Dodge Challenger 5.7L V8 gets iron block requirement, 10.5:1 compression max, intake valve 12.7 mm, exhaust 12.3 mm, intake duration 188°, exhaust duration 205°. · AS Dodge Challenger 08-14 rear spoiler part number changes from 1GL20RXF to 1GL20TZZAB. · SM rear brake calipers may use single bracket under upper retaining bolt to prevent pin failure. · T1 rear wing Gurney flap wording clarified: Gurney flap in chord length and mounting height rules. · T4 Scion FRS and Subaru BRZ Solo Spec Coupe final drive ratio changed from 4.30 to 4.10. · AS class pursues specified list of eligible tires; details of tire changes not provided in letter. · AS class pursuing specified list of eligible tires; details pending further communication. · No restrictor plate change implemented; 2021 AS Mustang Coyote under evaluation. · AS 2005-2009 Restricted Prep 4.6 3V now permits conversion to 2 valve configuration. · AS Ford Mustang Coupe GT 4.6L 3V Restricted Prep now permits Ford Performance camshaft kit P/N-M-6550-3V. · 2010-2014 Camaro reclassified to AS; full preparation classification approved effective 2020-07-01. · AS class cylinder head replacement options under review; implementation planned for 2021 season. · AS Mustang, Camaro, Firebird, Capri max brake rotor diameter increases from 12.2 to 13.1 inches. · AS rotor diameter increase approved; see Fastrack letter #28748 for details. · T4 Mazda RX-8 04-12 now allows OE rear spoiler #F151-V4-920F and OE front air dam #F151-V4-900f-BB. · T4 2006-2015 Mazda MX-5 Club Model now allows non-stock wheels; transmission, differential, LSD remain stock. · Cannot read: letter references external document #27663 not provided. · T1 and T2 Corvettes may convert leaf spring suspension to coilover with 800 lb max spring rate allowed. · 2004 Mercedes Benz CLK 320 Coupe classified in T4 at 3200 lbs with 3299cc engine and Eibach PN# 2563.140 springs allowed. · AS Chevrolet/Pontiac Camaro & Firebird (82-92) loses 50 lbs, to 3500. · T1 Porsche 996 GT3 Cup eligible model years changed from 2002-2005 to 1998-2004. · T1 Corvette and Cadillac XLR permitted to install SCRSPLR-001 rear spoiler with OE bodywork. · T1 Gen 5 Camaro allowed 366mm OEM rear rotor and caliper without weight penalty. · T4 06-15 Mazda MX-5 now allows header part numbers 0000-06-5407 or 0000-06-5407-NC. · T3 BMW Z3 M & Coupe 1998-1999 weight reduced from 3350 to 3150 lbs. · T1 Porsche 996 Spec Lines now allows 996 Cup Replica Rear deck lid. · T1 Acura NSX Turbo World Challenge and Audi TTRS GTS 2011 now require DOT tires per GCR section 9.3. · T1 BMW E46 wagon with S54 engine allowed; displacement corrected from 3200 to 3250cc. · T4 Honda Civic Si 12-13 and 14-15 now allow H&R and HPD springs up to 700 pounds with 47mm restrictor. · T4 Ford Mustang V6 05-10 springs now permitted max 500 lbs front and 400 lbs rear. · AS rear trailing arms may be replaced with tubular arms maintaining stock length and axle location purpose only. · AS Ford and GM full-prep cars get 200 lb weight reduction, up from 150 lb. · 05-10 Ford Mustang Coupe GT 4.6L OHC classified AS with 3200 lbs minimum weight, HR cam restricted prep. · AS 10-15 Chevrolet Camaro Full Prep classified with 3400 lbs base weight, over 313 CID engine 3700 lbs maximum. · T1 adds Subaru WRX/WRX STI 2005-2020 at 3000 lbs minimum weight with 46 mm restrictor. · T1 Ford Mustang GT (15-17) and GT5.0L (2018-) weight raised to 3500 lbs; Brembo BBK 380mm now at no penalty; restrictors removed from notes. · T1 Ford Mustang/Thunderbird 5000 Coyote OEM reclassified to include 2015–2017 and 2018+ model years with 65mm restrictor for 18+. · T1 BMW M3 E92 carbon dash allowed with 25 lb penalty. · T1 Corvette C5 Z06, C6 coupe, C6 Grand Sport, and Z06 may convert leaf springs to conventional coilover suspension. · T4 Ford Mustang V6 05-10 allowed aluminum driveshaft, any LSD, and Ford brake kit M-2300-D. · Pontiac Solstice GXP and Saturn Sky move from T2 to T3; wheels widen to 18 x 9.5 inches, Sky weight drops to 3200 lbs. · Mazda RX-8 Base/R3/Sport/GT (04-12) classified in T3 effective 2020-02-01. · T4 Mazda3 14-18 gains permitted modifications: springs to 800/1000 lbs, 15 lb wheels, cold air intake, camber plates, 25mm rear bar, mirrors, CorkSport arms, header, specific calipers and rotor. · T4 allows aftermarket OEM coolant expansion tanks with no other functional purpose. · T4 Mazda MX-5 Club Model 06-15 now allows aftermarket power steering reservoir. · T4 Subaru BRZ and Scion FR-S allowed factory installed wings. · T4 now permitted to use any OEM diameter clutch disc and pressure plate, previously T2-T3 only. · Chevrolet Sonic 2011+ added to T4 at 2800 lbs with 1364 cc engine and 225 max tire size. · T4 Mazda MX-5/Miata 1999-2005 minimum weight reduced 50 lbs to 2400. · T2 requires onboard fire system; T3 and T4 may have one per GCR 9.3. · T3 Ford Mustang EcoBoost 2015- gains three transmission gear ratio options. · T4 BRZ, FR-S, and 86 maximum tire size reduced from 245 to 225. · T4 Mazda MX-5 Club Model 06-15 minimum weight cut from 2625 to 2550 lbs. · Mazda RX-8 Base/R3 (04-12) reclassified in T3 and T4 to include Sport and GT variants. · Toyota 86 GT (2017-) added to T3 and T4 Spec Line. · AS Spec Mustang (SMG) added as Restricted Prep class. · T1-LP Chevrolet Camaro 1LE 2016- weight drops to 3500 lbs, restrictor increases to 70mm flat plate. · T2-T4 spare tire/wheel rules clarified: removable covers can be removed with hardware and bracketry. · T4 Mazda MX-5 Club (06-15) gains suspension package with 100 lbs weight increase, allows RX8 hubs and SM5 suspension, permits non-OEM LSD with 50 lbs penalty. · AS class minimum ride height clarified to 5 inches measured at rocker panel, excluding seams and cladding. · Ford Mustang Challenge returns to T1 as E&O, 4600 cc, 3300 lbs minimum, no restrictor. · T1 Chevrolet Corvette Cadillac XLR year range corrected from 04-09. · T1 Camaro, CTS, Firebird, GTO restrictor increases from 67mm to 70mm flat plate. · T4 Toyota MR-2 Spyder 16V DOHC years corrected from 01-05 to 00-07. · AS Ford Mustang (79-93) 313 CID and under loses 100 lbs to 3150; over 313 CID loses 100 lbs to 3450. · T2-T4 clarifies DOT tire requirements; must have minimum U speed rating and be DOT certified; touring spec line supersedes other rules. · T4 Mazda Protégé ES 2000 now allows piggyback ECU tuning device; OBD2 requirement waived. · T4 Mazda MX5 Club Model 06-15 allows suspension package with 100 lbs weight increase including helper springs. · Ford Mustang EcoBoost 3.5L classified in T1 at 3300 lbs minimum weight with 31mm restrictor. · T1 Corvette C5 body allowed C7 carbon aero parts, plus 50 lbs. · T1 Audi TTRS must conform to July 24th, 2015 revision 7 GTS rules instead of December 14th, 2011 revision 3. · T1 minimum ride height established at 3.5 inches, measured at rocker panel without driver. · T1 Porsche 928 S4/GTS-R minimum weight reduced to 3200 lbs, throttle restrictor removed. · Porsche 928 S4/928 GTS-R newly classified in T1 at 3500 lbs minimum with 60mm flat plate restrictor. · T4 BMW 323 (98-00) newly classified at 3450 lbs with 50mm flat plate restrictor and M52TUB25 engine required. · SM fuel pump and filter must be Mazda or OEM Equivalent part. · T1-LP Ford Mustang GT 5.0L 2018+ classified at 3400 lbs with 65mm flat plate restrictor. · T4 Mazda MX-5 Club (06-15) and (2016-), T3 MX-5 Cup and Miata (2016-) hardtop rules clarified; wording changes to permitted parts and specifications. · T2, T3, T4 now allow any thermostat serving only OE intent, previously restricted. · T3 and T4 Mazda MX-5 Miata eligibility capped at 2018 model year, effective 2019-03-01. · AS Spec Mustang (SMG) newly classified with 107.1 wheelbase, 3.73 gears, 355mm front brakes, 300mm rear. · SM 1999-2000 model year cars may use replacement Mazda ECU and injector harnesses, unmodified. · SM electrical rules reorganized and clarified; alternator external regulation now prohibited except via OEM ECU/kill switch. · SM removes tire tread protrusion beyond fender opening requirement from GCR 9.1.7.C.5. · T4 Honda Civic Si 2012-2015 permitted sway bars increased to 32mm front and rear. · T1-LP Mustang GT350(R) spec line replaced with 2015+ model parameters including 5163cc engine, 3650 lbs curb weight, 315 tire size. · Ford Mustang FP350S (2018) classified in T1-LP at 3600 lbs with 18×11 wheels and 315 tires. · T1 suspension rules clarified: spherical bearings and bushings now explicitly permitted, alternate control arms allowed. · T1 Porsche 996 drops 200 lbs to 3000; 996 GT3 Cup drops 150 lbs to 3000; 997 drops 50 lbs to 3100. · Porsche 997 T1 Maximum now allows OEM PDK transmission alongside existing drivetrain options. · T1 Acura NSX Turbo World Challenge weight to 3100 lbs, restrictor to 44mm. · T1-T3 spec cars receive clarifications on permitted modifications, documentation requirements, and rule conformance; no performance changes. · T4 Ford Fiesta ST years corrected to 14-; T4 Fiat 124/Abarth Edition years added 16-18; battery rule clarified. · T4 Fiat 124 Abarth Edition restrictor changes from 29mm flat plate to 30mm TIR. · T1-T3 spec cars receive clarifications on permitted modifications, documentation requirements, and rule conformance; no performance changes. · T2-T4 subframe bushings may now be replaced with non-spherical bushings of any material. · Scion FR-S and Subaru BRZ 13-16 Solo Spec Coupes added to T4, both 1998cc, 2570 lbs, 225/45/17 tires.showhide
T1 Corrections to T1 Spec Lines #33678tyres & wheelsunclearGT4 McLaren 570S maximum tire size changes to 285 front, 315 rear.
T4 Mustang OEM Grill Request #33333aeroaeroT2/T3 Mustang GT 5.0L and V6 (11-14) may remove upper grille fog lights, replace with mesh or screen.
T4 Mazda OEM LSD was letter 32655 typo #33666wordingwordingT4 Mazda MX-5 Club Model 06-15 Mazda Motorsports LSD part number corrected from 32655 to 0000-02-5564.
SM BOP for NB1 and NB2 #32309weightslowerSM Mazda MX-5 Miata 01-05 weight increases to 2450 lbs, or 2465 with alternate bore.
T1 GT4 section to Current T1 Rules. #33632cars addedcars addedEight GT4 models added to T1 with weights from 3200 to 3575 lbs and restricted power per SRO 2022 rules.
T4 Allowable Springs and Sway Bars for 06-11 Civic si Spec Line #33294suspension & brakesfasterT4 Honda Civic Si 06-11 now permits 32mm sway bars front and rear and 700 pound springs.
T4 Touring (T2-T5) Category #33617cars addedcars addedT5 class added as regional-only; T5 tyres maximum width 225, minimum aspect ratio 45.
T4 ENO 9.1.9.2.D.1.e.1.a. #33651suspension & brakessuspension & brakesT2-T5 Touring front and rear suspension maximum negative camber changed to 3.5 degrees.
T4 T4 mustang #32789tyres & wheels -25 lbsfasterT4 Ford Mustang V6 (05-10) wheels widen to 18x9, front brakes grow to 314mm vented, weight drops to 3275 lbs.
T4 Mazda OEM LSD was letter 32655 #32933weight -25 lbsfasterT4 Mazda MX-5 Club (06-15) minimum weight drops 25 lbs to 2600; Mazda LSD #32655 now permitted without penalty.
T4 Another 2022 BRZ/86 T3 request #32945weight +225 lbsslowerT3 Subaru BRZ 2022- minimum weight up to 2975 lbs; spring rate to 1000 F/R, brake parts allowed without penalty.
AS Request to add Hoosier W2 #33031tyres & wheelstyres & wheelsAS allows Hoosier W2 tyre option in addition to R7, R6, WET/H20.
AS correction of Dodge Challenger specification line #33151wordingwordingAS Dodge Challenger 08-20 adds two transmission ratio options: 2.97, 2.10, 1.45, 1.00, 0.74, 0.50 or 2.26, 1.58, 1.19, 1.00, 0.77, 0.63.
T1 Correct Camaro Spec Line From Letter #30791 response to 3475lbs #32824weight -25 lbsfasterT1 Cadillac CTS/CTS-V, Chevrolet Camaro, Pontiac Firebird, Pontiac GTO 6162 OEM minimum weight reduced to 3475 lbs.
AS Request CTS-V Spec Line Error Correction #30242weightfasterAS Cadillac CTS-V 6.0L V8 removes 50 lbs weight penalty for 295 tire size.
T1 Fix FP350S limited prep and Shelby 350 full prep issues #31680inductionfasterT1-LP Ford Mustang FP350S restrictor increases from 70mm to 75mm.
T1 Request to Classify AMG GT4 #32610cars addedcars addedMercedes Benz AMG GT4 2017-2021 classified T1 Maximum at 3400 lbs minimum weight with HP-controlled SRO Power Level 2 engine.
T4 Request Wider Wheels for Hyundai Tiburon #32536tyres & wheelsfasterT4 Hyundai Tiburon V-6 wheel width increases from 7 to 8 inches at 17-inch diameter.
T4 Request to Add Spec Line for 2004-2009 Mazda3 i 2.0 #32395cars addedcars addedT4 Mazda3 i 2.0L added as spec line with 1999cc displacement and 2425 lbs minimum weight.
T4 Request Alternate Front & Rear Strut/Shock Top Hats #32452suspension & brakessuspension & brakesT2-T4 Touring cars with alternative springs may use performance top hats with spherical bearings on shocks and struts.
SM Update GCR Section 9.1.7.3.A.1. #32217wordingwordingSM Majors must run authorized Penske shock and mount; Regional competitors' requirement eligibility clarified.
T1 Viper/Z06 Parity #31942weight -50 lbsfasterT1 Dodge Viper ACR displacement rises to 8400 OEM, minimum weight drops to 3550 lbs.
T1 Discrepancy in T1 allowances #32293wordingwordingT1 Limited T1 wording changed to clarify all T1 cars permitted specifications.
T4 Request to Allow the Use of Aftermarket ECU's in Touring #31067weightslowerT2-T4 cars model year 2018+ may use non-OEM ECU with 75 lb weight penalty via spec line adjustment.
T4 Request JWT BSR Kit for 02-06 Nissan Sentra SE-R/Spec V #31685enginefasterT4 Nissan Sentra SE-R Spec V 02-06 now permits balance shaft removal kit OQR25-NOBAL.
T4 Please Confirm Touring 4 (98-00) BMW 323 is E46 generation #31972wordingunclearT4 BMW 323 (98-00) wheelbase increases to 2725 mm, final drive ratio changes to 3.07.
T4 RX-8 Spring Part Numbers (E&O) #32151suspension & brakessuspension & brakesT4 Mazda RX-8 04-12 gains Eibach spring alternatives to Mazda Motorsports springs front and rear.
T4 04-09 Mazda3 Tire Limit Clarification #32249tyres & wheelsfasterT4 Mazda3 04-09 tire size increases from 235 to 245.
T4 Shock Part Number Errors & Omissions #32252wordingwordingT4 Ford Mustang V6 05-10 shock part numbers corrected to 8741-1494SPORT front and 8241-1240SPORT rear.
T4 Update Solo Spec Coupe to latest '20 specs for Road Racing #32262wordingunclearT4 Scion FR-S and Subaru BRZ Solo Spec Coupes updated to 2020 specifications Rev 7/20.
T4 Request 2016 Mazda MX5 springs #32265suspension & brakesslowerT4 2016–18 Mazda MX-5 Miata/Club gains 100 lbs. for approved suspension package with specific springs.
T4 Reply to letter #31486/29879 T2-T4 Grill openings #31935aerofasterT2-T4 grill openings may remove non-metallic webbed false sections; 16 square inch limit removed.
T4 BRZ vs BRZ TS #32022wordingwordingT3 Spec Lines Subaru BRZ TS (13-21) added to class specification wording.
T4 MX-5 Durability Detailed #31102weightslowerT4 Mazda MX-5 Club 06-15 allows non-OEM LSD with +50 lbs penalty; removes stock transmission and differential requirements.
T4 Request Allowances for 2005 - 2010 Mustang #31624suspension & brakessuspension & brakesT4 2005-2010 Ford Mustang V6 now specifies Koni damper part numbers 8741.1494 front and 8741.1240 rear.
AS Proposed Revisions to SCCA GCR 2021 Appendix M, Part 3 #30295wordingwordingSMG long tube headers: Borla PN 17237 discontinued, Kooks PN 11312000 and American Racing PN MT3-05134300LSNC approved alternatives.
AS specification line consolidation and correction #31846wordingwordingAS Mercury Capri (79-86) removed as individual spec line, merged into Ford Mustang (79-93) spec line.
AS correction of SMG specification line #31847wordingunclearAS Spec Mustang SMG loses 3.73 gear ratio and 355/300 mm brake specification.
AS Alternate cylinder heads for full prep engine builds - Evaluation #31851engineunclearAS Chevrolet, Pontiac, Ford full prep engines now permit alternate cylinder heads with restrictor plate ALL26180 and 1.250 inserts ALL26186 for regional competition.
T4 Reply to letter 29879 T2-T4 Grill Openings #31486aerofasterT2-T4 clarified: grill opening area may increase max 16 sq in for radiator cooling only, retaining factory mesh shape.
T4 Please Adjust 98-00 BMW 323 Min Weight to Reflect Current Class #31595weight -200 lbsfasterT4 BMW 323 98-00 minimum weight drops to 3250 lbs, 50mm restrictor removed.
T4 Consolidate 12-13 and 14-15 Honda Civic Si spec lines for T4 #31596wordingwordingT4 Honda Civic Si consolidates 12-13 and 14-15 into single 12-15 spec line with updated suspension allowances.
T4 Request to clarify radiator hoses #31682wordingwordingT2, T3, T4 radiator and coolant hoses may be replaced with aftermarket options; coolant temp sensor modification permitted.
T4 Clarify Permitted/Allowed #31743wordingwordingT2, T3, T4 clarify that spec lines listing permitted or allowed parts are alternatives to category rules, not replacements.
T4 Correct RSX wording #31746wordingfasterT4 Acura RSX/RSX Type-S 02-06 removes requirement that original wheels must remain stock.
T4 Camaro #31751suspension & brakesfasterT4 Chevrolet Camaro V-6 (96-02) removes requirement that shock/struts, mounts, and transmission differential remain stock.
T1 Turbo Miata Help #31315weight +200 lbsslowerT1 Mazda MX-5 Miata MazdaSpeed minimum weight rises to 2550 lbs, restrictor increases to 42mm.
T1 Fix the T1 Corvette heading #31528wordingwordingT1 Chevrolet Corvette Cadillac XLR classified for model years through 2019.
T4 Nissan Sentra SE-R Spec. V #30958cars addedcars addedNissan Sentra SE-R Spec V (2007–2012) newly classified in T4 at 3000 lbs minimum weight.
T4 Mazda RX-8 Spec Line Suspension Parts #31113suspension & brakesfasterT4 Mazda RX-8 04-12 allows alternate sway bars max 32mm front, 19mm rear; removes 60mm restrictor requirement.
T4 Diverter Valve Plunger Upgrade #31307wordingwordingT4 BMW 320i (14-15) now allows GFB T9357 aluminum diverter valve.
T4 Adjust Honda FWD in T4 to encourage more Drivetrain Diversity #31472tyres & wheelsfasterT4 Honda Civic FWD gets wider 8-inch wheels, 245 tyres max, and sway bar allowances to 29mm front, 22mm rear.
T4 Touring 4 BOP adjustments for 2022 #31482weight -175 lbsslowerT4 multiple cars: Volkswagen Rabbit 2.5 (08-09) to 2675 lbs; Mazda MX-5/Club (06-15) to 2625 lbs; RX-8 to 3125 lbs; Honda/Acura/Chevy/Mazda wheel widths 7 to 8 inches.
T4 Request to Classify 2014 VW Jetta 1.8t TSI #30436cars addedcars addedT4 Volkswagen Passat, Jetta 1.8T adds 2014 model year to eligible years.
AS Request for adjustable Front Upper Control Arms on 4th Gen F-Body #30457suspension & brakessuspension & brakesAS Chevrolet/Pontiac Camaro & Firebird 93-02 now allow BMR AA004 or UMI 2310 adjustable front upper control arms.
AS Request Pontiac GTO tire size change #30881weightslowerAS Pontiac GTO 04-06 LS1 to 3300 lbs, LS2 to 3350 lbs on 295 tire.
T1 T1 E46 BOP E&O for Letter # 29970 #30934weight +100 lbsslowerT1 BMW E46/E36/Z3 minimum weight increases to 2700 lbs, 3.4L engine car to 2750 lbs.
T1 Request BoP for the Viper in 1 LP #29968inductionfasterT1 Dodge Viper SRT-10 restrictor increases from 45mm to 57mm.
T1 LS6 Alternative Head Question #30074wordingwordingT1 Chevrolet Corvette Cadillac XLR LS6 engine now permits Casting #799 heads with no other head modifications.
T4 Wrong Part Number on 320i Spec Line #30645wordingwordingT4 BMW 320i 14-15 part number corrected from 20121.140 to E10-20-031-01-22.
AS Request CTS-V Spec Line Error Correction #30242weightfasterAS Cadillac CTS-V 6.0L V8 removes 50 lbs tire size penalty, making it lighter.
AS Request to consolidate SN95 Mustang '94-'04 Mustang spec lines #30428wordingwordingAS consolidates seven SN95 Mustang spec lines into three: 94-04 including Cobra, 94-95 5.0/5.8, and 96-04 4.6L two/four valve.
AS American Sedan Transmission Rule Change Request #30595enginefasterAS Camaro/Firebird LT1/LS1 transmission code changes to 6362; Mustang GT 4.6L/5spd changes to 5.0L/6spd with 300 lbs weight reduction.
AS Correction to specifications inadvertently deleted #30691wordingwordingAS Camaro/Firebird and Mustang GT gear ratio specifications restored with alternate sets permitted.
AS weight adjustments #30700weight +50 lbsslowerAS Chevrolet Camaro & Firebird, Ford Mustang variants, Mercury Capri minimum weights increase 50 lbs across all model years.
T1 T1-LP - Add Performance Pack, Bullet, Mach 1 to 18+ Mustang #29849inductionfasterT1 Ford Mustang Shelby/GT350/GT500 5.0L Coyote restrictor opens from 65mm to 70mm flat plate.
T1 Request BoP for the Viper in 1 LP #29968inductionfasterT1 Dodge Viper SRT-10 restrictor increases from 45mm to 57mm.
T1 Request to classify C7 and 13Viper in T1 LP #29969inductionfasterT1-LP Chevrolet Corvette C7 restrictor increases from 70 to 73 mm.
T1 Request LP Z06 steel chassis #30589wordingwordingT1-LP Corvette Z06 06-13 now allows aluminum chassis replacement with equivalent OE steel chassis.
T4 Civic Type R Brake Rotors #29817weightslowerT3 Honda Civic Type-R 2020+ allows brake rotor 45251-TGH-A01 with 25 lb penalty.
T1 Request For Reduction in Weight/Penalties for Camaro #30443weightfasterT1 Chevrolet Camaro with 6162 displacement minimum weight reduced to 3500 lbs.
T1 Fix dry sump Contradictions in T1-LP vs T2 #30596wordingwordingT1-LP Chevrolet Corvettes C5 Z06, C6 Grand Sport, and Z06 dry sump kit notes clarified to remove contradictions.
T4 Mini Cooper Spec Line Anomalies #30478suspension & brakesunclearT4 Mini Cooper S (02-04, 05-06) suspension/wheel rules simplified; (07-13) gear ratios changed to 3.31, 2.13, 1.48, 1.14, 0.95, 0.82, final drive to 3.65, brakes to 280 mm.
T4 Request CAI Mustang in T4 #30562inductionfasterT4 Ford Mustang V6 05-10 now allows cold air intake.
SM Updates - Obsolete Parts & BOP Parts #30438wordingwordingSM adds procedures for testing obsolete part replacements and BOP updates in sanctioned events with CRB approval.
T4 Request consistency review in GCR #30263wordingslowerT2-T4 clutch disc and pressure plate must be at least 95% of factory OEM weight.
AS AS Mustang LP 4.6 3V Classification Transmission Request #29886weightfasterAS Mustang 4.6L/5spd loses 300 lbs; 5.0L/6spd gains 56mm restrictor requirement.
AS Request CF driveshaft on CTS-V for durability improvement #30117otherotherAS CTS-V LS6 and LS2 may now use Driveshaft Shop carbon fiber driveshaft for durability.
AS Adjustment to model years of 5th generation RP Camaro #30348wordingwordingAS Chevrolet Camaro SS V8 6.2L model years extended from 10-13 to 10-15.
T1 T1 LP Aero adjustments #30196aerounclearT1 LP removes 50 lbs weight allowance for stock headers, adds aero device allowance up to 100 lbs, permits headers.
T4 E & O T4 Mustang Wheels #30245tyres & wheelsfasterT4 Ford Mustang V6 05-10 wheels increase from 17 to 18 inches.
T1 Request to Clarify Miller Mustang Classification #28728engineunclearT1 Ford Mustang Challenge 3-valve maximum displacement changes to 4600/5000.
T1 BMW E46 Carbon Dash #29806weightslowerT1 BMW E46 now allows carbon or fiberglass OEM-style dashboards with 25 pound penalty.
T1 Request to Update T1 Mustang Spec Line #30001wordingwordingT1 Ford Mustang/Thunderbird limited to Shelby/Shelby GT350/GT500 models through 2018.
T1 Class BMW M2CS Club Sport #30195cars addedcars addedBMW M2CS Club Sport classified in T1-LP Spec Lines effective 2021-02-01.
T1 997.1 GT3 Cup #30229cars addedcars addedPorsche 997.1 GT3 Cup (2006-2011) classified in T1 at 3600cc, 3150 lbs minimum weight.
T4 2021 Toyota Supra #29567cars addedcars addedToyota Supra 2020- newly classified in T2 at 3450 lbs minimum weight with 295 tire and 19-inch wheels.
T4 06-15 MX-5 Durability #29781wordingwordingT4 Mazda MX-5 durability rule now applies to T2-T4 instead of T2-T3 only.
T4 Request for Update to T4 Spec Line for Chevrolet Sonic (2011-) #29838wordingwordingT4 Chevrolet Sonic (2011-) spec clarified: 28mm TIR restrictor placement, PCV plug requirement, and allowed suspension parts listed.
T4 NC MX-5 06-15 Part Number updates for 2021 #29921wordingwordingT4 Mazda MX-5 06-15 removes front and rear end links from suspension package spec.
T4 BMW Z4 2.5L (03-05) Spec Line #30037weight -50 lbsfasterT4 BMW Z4 2.5L (03-05) minimum weight reduced from 3100 to 3050 lbs.
T4 Sway Bars for T4 2016+ MX5 Mazda #30063suspension & brakessuspension & brakesT4 2016+ Mazda MX-5 Miata gains allowance for 29mm front and 16mm rear sway bars.
T4 Change part numbers on BRZ, FRS lines in T4 #30104wordingwordingT4 Scion FR-S, Subaru BRZ, and Toyota 86 replace Eibach part 4.10582.880 with 82105.320, 4.10582 and SPC 67660.
T4 T4 Mustang Axle Ratio and Wheels #30149weightslowerT4 Ford Mustang V6 05-10 allows GT 8.8 rear axle with 3.45 or 3.55 ratio at +25 lb penalty.
AS Request for 2015 -2017 Ford Mustang Spec Line #29514cars addedcars addedFord Mustang GT 5.0L 15-17 Restricted Preparation classified in AS with 55mm flat plate restrictor required.
AS Request Trunk lid / Rear Hatch clarification #29591wordingwordingAS underhood bracing on stock hoods, trunks, and rear decks may be modified or removed.
AS Common Weight for CTS-V Tire #29759weightfasterAS Cadillac CTS-V 04-07 with 295 tire drops to 3450 lbs; Camaro SS V8 10-13 275 tire removed; Challenger 08-20 gains 315 tire option at 3600 lbs.
AS Correction to specifications inadvertently deleted #30041weightfasterAS Camaro & Firebird (93-02) and Mustang GT (05-14) specifications restored with 200 lb weight reduction for permitted heads.
T1 Correct T1 Limited Prep Years #29708wordingwordingT1 Chevrolet Corvette Z06 years extended from 06-12 to 06-13.
T4 Request to Classify BMW M2 CS #29523cars addedcars addedBMW M2 CS Cup 2020+ classified in T2 at 3625 lbs with 2979cc engine, 10.5x18 wheels, 295 tires.
T4 Allow the SpecMX-5 Update Kit Into Touring 4 for the MX-5 #29681wordingunclearT3 and T4 Mazda MX-5 06-15 now allow Mazda Transmission kit part # 0000-02-5700.
T4 Request Mustang 8.8†rear axle replacement #29860weightslowerT4 Ford Mustang V6 05-10 allows GT 8.8 rear axle with 3.55 final drive, adds 25 lb penalty.
T4 Cap year range on all 86s #29908wordingwordingT3 and T4 FR-S, 86, and BRZ year ranges capped: T3 at 2021, T4 at 2017-2021.
AS Request Additional Engine Options for Dodge Challenger Spec Line #29543engineslowerAS Dodge Challenger 08-20 gains 6.1L and 6.4L V8 options; 5.7L weight rises to 3500 lbs on 295 tyres, 3600 on 315 tyres.
AS Rule simplification spec line communization #29824wordingfasterAS Camaro/Firebird (93-02) and Mustang Coupe GT (05-14) consolidated into single specs with 100 lb and 300 lb weight reductions respectively.
T1 Changes to Corvette C8 #29898tyres & wheels -100 lbsfasterT1 Corvette C8 Z51 gets wider wheels and tyres, weight drops 100 lbs to 3550.
T4 Alfa Romeo 4C Launch Edition #29531wordingwordingT3 Alfa Romeo 4C Launch Edition now allowed in Spec Lines.
T4 Post Runoffs Feedback for T4 #29752tyres & wheels -50 lbs
SM Radiator E&O Clarifications #29294wordingwordingSM aftermarket radiators must mount in original location, maintain core plane, require no body modifications, block openings, keep one OEM fan in stock location; 1990-1997 cars may install upper radiator seal NA75-50-OK7A.
AS Dodge Challenger AS Spec Line Clarification #28698engineslowerAS Dodge Challenger 5.7L V8 gets iron block requirement, 10.5:1 compression max, intake valve 12.7 mm, exhaust 12.3 mm, intake duration 188°, exhaust duration 205°.
AS Dodge Challenger AS Spec Line Clarification #2 #28699wordingwordingAS Dodge Challenger 08-14 rear spoiler part number changes from 1GL20RXF to 1GL20TZZAB.
SM Modifications to prevent failures of Rear Brake Caliper Pin #28953suspension & brakessuspension & brakesSM rear brake calipers may use single bracket under upper retaining bolt to prevent pin failure.
T4 Scion FRS Solo Spec Coupe Gear Ratio #29021otherfasterT4 Scion FRS and Subaru BRZ Solo Spec Coupe final drive ratio changed from 4.30 to 4.10.
AS Support for R-Type Specification Tires #27450tyres & wheelsunclearAS class pursues specified list of eligible tires; details of tire changes not provided in letter.
AS Spec Tire Request #27519tyres & wheelsunclearAS class pursuing specified list of eligible tires; details pending further communication.
AS Restrictor Plate Change for RP 2011+ Mustang with Coyote Engine #27675wordingunclearNo restrictor plate change implemented; 2021 AS Mustang Coyote under evaluation.
AS 2005-2009 Restricted Prep 4.6 3V #27908engineunclearAS 2005-2009 Restricted Prep 4.6 3V now permits conversion to 2 valve configuration.
AS Request for 2005-2009 Restricted Prep 4.6 3V Parts #27909wordingunclearAS Ford Mustang Coupe GT 4.6L 3V Restricted Prep now permits Ford Performance camshaft kit P/N-M-6550-3V.
AS Request for Full Preparation Classification for 2010-2014 Camaro #28030cars addedunclear2010-2014 Camaro reclassified to AS; full preparation classification approved effective 2020-07-01.
AS Cylinder Heads #28696wordingunclearAS class cylinder head replacement options under review; implementation planned for 2021 season.
AS Request for Max Rotor Diameter Change #28748suspension & brakesfasterAS Mustang, Camaro, Firebird, Capri max brake rotor diameter increases from 12.2 to 13.1 inches.
AS Request increase rotor diameter #28797suspension & brakessuspension & brakesAS rotor diameter increase approved; see Fastrack letter #28748 for details.
T4 T4 RX8 bodywork clarification #28941aeroaeroT4 Mazda RX-8 04-12 now allows OE rear spoiler #F151-V4-920F and OE front air dam #F151-V4-900f-BB.
T4 2006-2015 MX-5 Clarification #28942otherfasterT4 2006-2015 Mazda MX-5 Club Model now allows non-stock wheels; transmission, differential, LSD remain stock.
T4 Request to Add a Vehicle to the Roster (contd.) #27698cars addedunclearCannot read: letter references external document #27663 not provided.
T1 Consider coil spring conversion Corvette in T2 #28824suspension & brakessuspension & brakesT1 and T2 Corvettes may convert leaf spring suspension to coilover with 800 lb max spring rate allowed.
T4 Request to Classify 2004 Mercedes Benz 320 CLK #27663cars addedcars added2004 Mercedes Benz CLK 320 Coupe classified in T4 at 3200 lbs with 3299cc engine and Eibach PN# 2563.140 springs allowed.
AS weight adjustments for 2020 season #28785weight -50 lbsfasterAS Chevrolet/Pontiac Camaro & Firebird (82-92) loses 50 lbs, to 3500.
T1 Additional Clarification on 996 Cup in T1 From Letter #28040 #28060wordingwordingT1 Porsche 996 GT3 Cup eligible model years changed from 2002-2005 to 1998-2004.
T1 Request SPEC Corvette Rear Spolier #28182aeroaeroT1 Corvette and Cadillac XLR permitted to install SCRSPLR-001 rear spoiler with OE bodywork.
T1 T1 Rear Brake Rotor Size Exemption for Gen 5 Camaro #28402wordingwordingT1 Gen 5 Camaro allowed 366mm OEM rear rotor and caliper without weight penalty.
T4 Request to change allowed header part # for T4 06-15 Miata #28223wordingwordingT4 06-15 Mazda MX-5 now allows header part numbers 0000-06-5407 or 0000-06-5407-NC.
T4 Z3M Roadster Weight #28437weightfasterT3 BMW Z3 M & Coupe 1998-1999 weight reduced from 3350 to 3150 lbs.
T1 Request 996 GT3 Trunk for Wing Allowance. #28153wordingwordingT1 Porsche 996 Spec Lines now allows 996 Cup Replica Rear deck lid.
T1 All Touring, Change DOT Tire Language 9.1.9.1, 9.3.45 #28452wordingwordingT1 Acura NSX Turbo World Challenge and Audi TTRS GTS 2011 now require DOT tires per GCR section 9.3.
T1 Request for E46 wagon with S54 engine in T1 #27427wordingwordingT1 BMW E46 wagon with S54 engine allowed; displacement corrected from 3200 to 3250cc.
T4 Request for 12-13 and 14-15 Honda Civic Springs #27848wordingwordingT4 Honda Civic Si 12-13 and 14-15 now allow H&R and HPD springs up to 700 pounds with 47mm restrictor.
T4 Request to Clarify T4 05-10 Mustang Spring Allowance #27899suspension & brakessuspension & brakesT4 Ford Mustang V6 05-10 springs now permitted max 500 lbs front and 400 lbs rear.
AS Rear Trailing Arms #28007suspension & brakessuspension & brakesAS rear trailing arms may be replaced with tubular arms maintaining stock length and axle location purpose only.
AS Weight reduction for cars running iron heads #28010weightfasterAS Ford and GM full-prep cars get 200 lb weight reduction, up from 150 lb.
AS 05-10 Mustang with HR cam classification #28226cars addedcars added05-10 Ford Mustang Coupe GT 4.6L OHC classified AS with 3200 lbs minimum weight, HR cam restricted prep.
AS 10-15 Camaro Full Prep classification #28227cars addedcars addedAS 10-15 Chevrolet Camaro Full Prep classified with 3400 lbs base weight, over 313 CID engine 3700 lbs maximum.
T1 Request to include Subaru WRX/STI 02-18 in T1 #24916cars addedcars addedT1 adds Subaru WRX/WRX STI 2005-2020 at 3000 lbs minimum weight with 46 mm restrictor.
T1 Request Ford Mustang FP350S T1-LP weight and restrictor change #26662weight +100 lbsslowerT1 Ford Mustang GT (15-17) and GT5.0L (2018-) weight raised to 3500 lbs; Brembo BBK 380mm now at no penalty; restrictors removed from notes.
T1 Request to classify Ford Coyote 3rd Gen OEM #27145cars addedslowerT1 Ford Mustang/Thunderbird 5000 Coyote OEM reclassified to include 2015–2017 and 2018+ model years with 65mm restrictor for 18+.
T1 Request alternate dashboard #27276weightslowerT1 BMW M3 E92 carbon dash allowed with 25 lb penalty.
T1 Request for Allowance of Coil Springs on Limited Prep C6 Corvette #27713suspension & brakesfasterT1 Corvette C5 Z06, C6 coupe, C6 Grand Sport, and Z06 may convert leaf springs to conventional coilover suspension.
T4 Request to Allow Brake Upgrade on T4 Mustang #27329otherotherT4 Ford Mustang V6 05-10 allowed aluminum driveshaft, any LSD, and Ford brake kit M-2300-D.
T4 Please Switch the Solstice GXP as Specified in T2, to T3 #27413cars added -50 lbsfasterPontiac Solstice GXP and Saturn Sky move from T2 to T3; wheels widen to 18 x 9.5 inches, Sky weight drops to 3200 lbs.
T4 Request to Classify all Mazda RX8 Models in T3/T4 #27606cars addedcars addedMazda RX-8 Base/R3/Sport/GT (04-12) classified in T3 effective 2020-02-01.
T4 Request for 2014-2018 Mazda 3 GT Brakes #27659suspension & brakesfasterT4 Mazda3 14-18 gains permitted modifications: springs to 800/1000 lbs, 15 lb wheels, cold air intake, camber plates, 25mm rear bar, mirrors, CorkSport arms, header, specific calipers and rotor.
T4 Request to allow aftermarket OEM coolant expansion tank #27763wordingwordingT4 allows aftermarket OEM coolant expansion tanks with no other functional purpose.
T4 Request to allow aftermarket OEM power steering reservoir #27764wordingwordingT4 Mazda MX-5 Club Model 06-15 now allows aftermarket power steering reservoir.
T4 Request for Factory Installed Wings on Subaru BRZ #27831wordingwordingT4 Subaru BRZ and Scion FR-S allowed factory installed wings.
T4 Request for Replacement Clutches #27892wordingwordingT4 now permitted to use any OEM diameter clutch disc and pressure plate, previously T2-T3 only.
T4 Request to Classify Chevy Sonic 1.4 In T4 #27906cars addedcars addedChevrolet Sonic 2011+ added to T4 at 2800 lbs with 1364 cc engine and 225 max tire size.
T4 Clarification of On-Board Fire System for T2 #27183wordingwordingT2 requires onboard fire system; T3 and T4 may have one per GCR 9.3.
T4 Mustang Ecoboost and GT Transmission #27439otherunclearT3 Ford Mustang EcoBoost 2015- gains three transmission gear ratio options.
T4 BRZ/FRS/86 Tire Size in T4 #27660tyres & wheelsslowerT4 BRZ, FR-S, and 86 maximum tire size reduced from 245 to 225.
T4 NC MX5 2006-2015 Spec Adjustment Request #27739weight -75 lbsfasterT4 Mazda MX-5 Club Model 06-15 minimum weight cut from 2625 to 2550 lbs.
T4 T4 RX8 Classification Error #27902wordingwordingMazda RX-8 Base/R3 (04-12) reclassified in T3 and T4 to include Sport and GT variants.
T4 Request to add Toyota 86 GT to Spec Line #27910cars addedcars addedToyota 86 GT (2017-) added to T3 and T4 Spec Line.
AS Request to add SMG to 9.1.6.B.1 AS Intent #27140cars addedcars addedAS Spec Mustang (SMG) added as Restricted Prep class.
T1 T1 LP 2016 Camaro and Later #27198weight -100 lbsfasterT1-LP Chevrolet Camaro 1LE 2016- weight drops to 3500 lbs, restrictor increases to 70mm flat plate.
T4 Request spare tire/wheel clarification #27012wordingwordingT2-T4 spare tire/wheel rules clarified: removable covers can be removed with hardware and bracketry.
T4 Research E&O Mazda MX5 #27112suspension & brakesslowerT4 Mazda MX-5 Club (06-15) gains suspension package with 100 lbs weight increase, allows RX8 hubs and SM5 suspension, permits non-OEM LSD with 50 lbs penalty.
AS Request Ride Height Clarification #26598wordingwordingAS class minimum ride height clarified to 5 inches measured at rocker panel, excluding seams and cladding.
T1 Request to return Ford Mustang Challenge Car to T1 #26751cars addedcars addedFord Mustang Challenge returns to T1 as E&O, 4600 cc, 3300 lbs minimum, no restrictor.
T1 Correct years in T1 FP Corvette spec #27023wordingwordingT1 Chevrolet Corvette Cadillac XLR year range corrected from 04-09.
T1 Request BoP Baten - T1 Camaro - Follow up to Letter # 26145 #26900inductionfasterT1 Camaro, CTS, Firebird, GTO restrictor increases from 67mm to 70mm flat plate.
T4 MR2 Spyder Year Correction #26936wordingwordingT4 Toyota MR-2 Spyder 16V DOHC years corrected from 01-05 to 00-07.
AS Request to Revert to 2017 Weights #25885weightfasterAS Ford Mustang (79-93) 313 CID and under loses 100 lbs to 3150; over 313 CID loses 100 lbs to 3450.
T1 Clarify DOT tires touring #26556tyres & wheelstyres & wheelsT2-T4 clarifies DOT tire requirements; must have minimum U speed rating and be DOT certified; touring spec line supersedes other rules.
T4 Request to allow piggy back ECU on 2000 Mazda Protégé #26085enginefasterT4 Mazda Protégé ES 2000 now allows piggyback ECU tuning device; OBD2 requirement waived.
T4 Request helper spring as optional #26678suspension & brakesslowerT4 Mazda MX5 Club Model 06-15 allows suspension package with 100 lbs weight increase including helper springs.
T1 Request to Classify EcoBoost Mustang #25841cars addedcars addedFord Mustang EcoBoost 3.5L classified in T1 at 3300 lbs minimum weight with 31mm restrictor.
T1 Request Corvette aerodynamic aids #26265aeroslowerT1 Corvette C5 body allowed C7 carbon aero parts, plus 50 lbs.
T1 Audi TTRS VTS Documentation Revision #26578wordingunclearT1 Audi TTRS must conform to July 24th, 2015 revision 7 GTS rules instead of December 14th, 2011 revision 3.
T1 Request Ride Height Clarification #26599wordingwordingT1 minimum ride height established at 3.5 inches, measured at rocker panel without driver.
T1 Request to classify the Porsche 928GTS/S4 in Touring 1 #26315cars addedcars addedPorsche 928 S4/928 GTS-R newly classified in T1 at 3500 lbs minimum with 60mm flat plate restrictor.
T4 Request to classify 2000 - 2001 BMW 323 #25096cars addedcars addedT4 BMW 323 (98-00) newly classified at 3450 lbs with 50mm flat plate restrictor and M52TUB25 engine required.
SM Request to allow aftermarket fuel filters. #26370wordingwordingSM fuel pump and filter must be Mazda or OEM Equivalent part.
T1 Request Mustang GT Limited Prep 2018 Classification #24431cars addedcars addedT1-LP Ford Mustang GT 5.0L 2018+ classified at 3400 lbs with 65mm flat plate restrictor.
T4 Correct Mazda MX-5 Hard Top Notes #26137wordingwordingT4 Mazda MX-5 Club (06-15) and (2016-), T3 MX-5 Cup and Miata (2016-) hardtop rules clarified; wording changes to permitted parts and specifications.
T4 Consider opening class rules to allow any thermostat #26187wordingwordingT2, T3, T4 now allow any thermostat serving only OE intent, previously restricted.
T4 Cap 2016 Mazda Miata year at 2018 #26388wordingwordingT3 and T4 Mazda MX-5 Miata eligibility capped at 2018 model year, effective 2019-03-01.
AS SMG Mustang eligibility in American sedan #26224cars addedcars addedAS Spec Mustang (SMG) newly classified with 107.1 wheelbase, 3.73 gears, 355mm front brakes, 300mm rear.
SM Request 99-00 replacement Wire harnesses #25602wordingwordingSM 1999-2000 model year cars may use replacement Mazda ECU and injector harnesses, unmodified.
SM Organize and Clarify 9.1.7.C.1.o. #25913wordingwordingSM electrical rules reorganized and clarified; alternator external regulation now prohibited except via OEM ECU/kill switch.
SM Strike Tire Tread Language #26123wordingwordingSM removes tire tread protrusion beyond fender opening requirement from GCR 9.1.7.C.5.
T4 2012-2015 Honda Civic Si Performance Request #26129suspension & brakesfasterT4 Honda Civic Si 2012-2015 permitted sway bars increased to 32mm front and rear.
T1 Class 2015+ Mustang GT350(R) #21466wordingwordingT1-LP Mustang GT350(R) spec line replaced with 2015+ model parameters including 5163cc engine, 3650 lbs curb weight, 315 tire size.
T1 Request to Classify Ford FP350S in T1-LP #25341cars addedcars addedFord Mustang FP350S (2018) classified in T1-LP at 3600 lbs with 18×11 wheels and 315 tires.
T1 Amendment to Request #25555 #25556wordingwordingT1 suspension rules clarified: spherical bearings and bushings now explicitly permitted, alternate control arms allowed.
T1 Request to balance 996 v 997 T1 weight #25658weightfasterT1 Porsche 996 drops 200 lbs to 3000; 996 GT3 Cup drops 150 lbs to 3000; 997 drops 50 lbs to 3100.
T1 Request to Add PDK Transmission to 997 Porsche Spec Line #25668wordingwordingPorsche 997 T1 Maximum now allows OEM PDK transmission alongside existing drivetrain options.
T1 T1 World Challenge/Grand AM Spec Cars #25687weightslowerT1 Acura NSX Turbo World Challenge weight to 3100 lbs, restrictor to 44mm.
T1 Add Clarification to Spec Car Classifications Vehicle Spec #25774wordingwordingT1-T3 spec cars receive clarifications on permitted modifications, documentation requirements, and rule conformance; no performance changes.
T4 Errors, Omissions, and Updates (Various) #22414wordingwordingT4 Ford Fiesta ST years corrected to 14-; T4 Fiat 124/Abarth Edition years added 16-18; battery rule clarified.
T4 Request for Adjustments to fiat 124 specline #25371inductionfasterT4 Fiat 124 Abarth Edition restrictor changes from 29mm flat plate to 30mm TIR.
T4 Add Clarification to Spec Car Classifications Vehicle Spec #25774wordingwordingT1-T3 spec cars receive clarifications on permitted modifications, documentation requirements, and rule conformance; no performance changes.
T4 Clarify Subframe Bushings Permitted for T2-T4 #25800wordingwordingT2-T4 subframe bushings may now be replaced with non-spherical bushings of any material.
T4 Consider Solo SSC cross over classification into T4 #25802cars addedcars addedScion FR-S and Subaru BRZ 13-16 Solo Spec Coupes added to T4, both 1998cc, 2570 lbs, 225/45/17 tires.
Best is the class's fastest lap in that event's qualifying or race sessions, with the driver who set it, how many cars set a time that session and how close the top five were; a best from fewer than three cars is greyed. With two or more classes, "vs" is the gap of each class's best to the first class's at the same event. "% of T1" is the class's best as a share of T1's best at the same event (100% is level, less is quicker): weather and track condition move every class together, so this compares across years where the raw times do not. It still breaks when T1's own field changes or one session was wet and another dry. Newest event first. The coloured figure under each value is the change from the previous event that has one (green is quicker, red slower). Whole laps only, so events with different sector layouts still compare. Weather and track condition are not accounted for.