STU at Road America

2020-12-01 STU Request clarification on wing measurement

#29640 from Jose De Miguel · Rule change · TB 20-12 (2020-12 Fastrack)

IN ST, GCR Section 9.1.4.D.4.e, add the following:
"Unless otherwise specified in the applicable rules the measurement of aero dynamic devices and reference areas shall include
end plates but not include fasteners as long as the fasteners serve no other purpose. Fasteners may protrude no more than 1/2”
from the mounting surface."

2021-01-01 STU 13B Rules Adjustment

#29333 from Nick Leverone · Rule change · TB 21-01 (2021-01 Fastrack)

In STU, remove Spec Line in entirety, Mazda 13B, weight 2300.
In STU, remove Spec Line in entirety, Mazda 13B Bridge Port, weight 2600.
In STU, classify Mazda 13B Street Port as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Mazda 13B Street Port N/A 2400 Allow any dual throttle
body/bodies. Chokes must be
located within 4” of the throttle
butterfly. Auto-type 2bbl choke(s)

2021-02-01 STU Brake Component Relocation

#29990 from Christopher Childs · Rule change · TB 21-02 (2021-02 Fastrack)

In ST, Section 9.1.4.N.1., add the following:
"ABS actuation hardware and wiring may be relocated anywhere within the engine compartment."

2021-02-01 STU Porsche PDK

#30081 from Michael Kamalian · Rule change · TB 21-02 (2021-02 Fastrack)

In STU, GCR Section 9.1.4.1.C.2., change as follows:
"Transmission and ratios are free. Forward gears are limited to 6 speeds. Cars equipped with automatic transmissions using a
torque converter a re limited to 8 forward speeds. Cars with sequential shift transmissions including factory DCT-type systems
shall increase the required minimum weight by 3.5%."

2021-02-01 STU Reference Letter #29333 Proposed STU 13B Spec Line Changes

#30086 from Scott Peterson · Rule change · TB 21-02 (2021-02 Fastrack)

In STU, Spec Lines, Mazda 13B Street Port 2400 Min Weight, change Notes as follows:
"Allow any dual throttle body/bodies. Chokes must be located within 4” of the throttle butterfly. Auto-type 2bbl choke(s) with
any dual-Y manifold. Unrestricted"

2021-02-01 STU Drive Shaft Request

#30087 from Scott Peterson · Rule change · TB 21-02 (2021-02 Fastrack)

In GCR, Section 9.1.4.L.1., change as follows:
"Alternate differential housings are permitted from the same model of vehicle. Differential may be open, locked, or of a limited-
slip type. The internals of limited-slip type differentials may be modified to change the amount of slip limiting. Differentials with
external, or electric, adjustability are prohibited. Driveshaft and half-shafts may be aftermarket, but shall be the OEM-type and
use the same types of materials as stock steel or aluminum. Drive shafts may be replaced by one piece drive shafts, and
conversely."

2021-03-01 STU Super Touring Alternate Miata Hubs

#30345 from Club Racing Board · Rule change · TB 21-03 (2021-03 Fastrack)

In ST, GCR section 9.1.4.M, add alternate front wheel hubs as follows:
"18. Allow alternate front wheel front hubs for the 90-05 Mazda Miata:
Mazda Motorsports Development Part #0000-04-5HUB-S1"

2021-04-01 STU Provision for Interchangeable Engine Components Already Allowed

#30342 from Justin Taylor · Rule change · TB 21-04 (2021-04 Fastrack)

In STU Spec Lines, Honda S2000, add to Notes as follows:
"F20/F22 K24 Crank Shaft allowed, must use chart weight for achieved displacement."

Applies to Honda S2000 on this page: Rylan Hazelton, James Mullen, Michael Reece

2021-04-01 STU ST Oil Coolers E&O Correction to 9.1.4.2.H

#30388 from Philip Royle · Rule change · TB 21-04 (2021-04 Fastrack)

In ST, section 9.1.4.G.14, change as follows:
"Vents, breathers, and oil filters and oil coolers may be added, or substituted. All emission control devices may be removed and
the resulting holes plugged."

2021-05-01 STU Request for Fender Flare Clarification

#30375 from David Mead · Rule change · TB 21-05 (2021-05 Fastrack)

In STU, section 9.1.4.1.A.4., change as follows:
"The exterior contour of all wheel openings Fenders may be flared up to a maximum of 2” per corner with a total 1% weight
penalty of 1%. The flare must maintain the OEM profile and appearance, seamlessly around the wheel arch. Material may be
added or removed as necessary to create flare. The fender/wheel opening or any other part of the body forming the wheel
opening, when viewed from the top perpendicular to the ground, must cover the portion of the tire that contacts the ground
while the car is at rest. The flaring of the exterior contour of any wheel openings may not alter the basic body configuration or
change the wheel opening size, location or shape when viewed from the side."

2021-07-01 STU STU Fender flares

#30696 from Patrick Lipsinic · Rule change · TB 21-07 (2021-07 Fastrack)

In STU, Section 9.1.4.1.A.4., change as follows:
"The flaring e of the exterior contour of any wheel openings may not change the wheel opening size, location or shape when
viewed from the side. The overall vehicle width may not exceed the manufacture's published width, plus 4"."

2021-07-01 STU Request weight reduction for 12A bridgeport motor in Miata

#30751 from christopher harris · Rule change · TB 21-07 (2021-07 Fastrack)

In STU Spec Lines Table B, Mazda 12A Street Port, change Notes as follows
"Induction: 1 Nikki 4 barrel carburetor with primary chokes bored to match secondary chokes on a stock manifold, or 1 Auto-
type 2 barrel carburetor with 42mm chokes on a "dual-y" manifold."
In STU Spec Lines Table B, Mazda 12A Bridge Port, change weight as follows:
"2550 2350"

2022-01-01 STU Request to Add Honda K23 Spec Line

#30682 from David Mead · Rule change · TB 21-08 (2021-08 Fastrack)

In STU, classify Honda K23 as follows, effective 1/1/2022:
STU Maximum Displacement (cc's) Minimum Weight Notes
Honda K23 2354 Chart May use K24 block. Must maintain all K23
internals. Must use K23 cylinder head.
Maximum bore of 87mm.

2022-01-01 STU RE: Aug FT letter 30682

#31060 from David Mead · Rule change · TB 21-09 (2021-09 Fastrack)

In STU, Honda K23, change Notes as follows, effective 1/1/2022:
"Must maintain all K23 internals. use K23 crankshaft."

2022-01-01 STU Throttling Device Clarification

#31323 from Jose de Miguel · Rule change · TB 22-01 (2022-01 Fastrack)

In GCR, Section 9.1.4.1.B.4., change as follows:
"The intake and exhaust porting on piston engines is free. Porting of intake manifolds and cylinder heads is free on piston
engines."

2022-02-01 STU Request Allowance for Balance Shaft Delete in STU

#31434 from David Fiorelli · Rule change · TB 22-02 (2022-02 Fastrack)

In GCR, Section 9.1.4.G., add as follows"
"29. Any engine balance shafts and associated gears or pulleys may be removed and the resulting openings plugged (including
those in oil passages). Alternate pulleys or gears, of the same number as stock, may be installed in the location of the balance
shaft pulleys or gears if required for timing belt or chain operation; they must serve no other purpose. Any engine balance shafts
and associated gears or pulleys may be removed and the resulting openings plugged (including those in oil passages). Alternate
pulleys or gears, of the same number as stock, may be installed in the location of the balance shaft pulleys or gears if required for
timing belt or chain operation; they must serve no other purpose."

2022-02-01 STU Request Louvers in hood vents

#31916 from David Fiorelli · Rule change · TB 22-02 (2022-02 Fastrack)

In GCR, Section 9.1.4.1 A.2., add as follows:
“Louvers within the 200 sq. inch are allowed.”

2022-03-01 STU Single TB Weight Modifiers

#31449 from John Weisberg · Rule change · TB 22-03 (2022-03 Fastrack)

Effective 5.1.2022 In STU, GCR Section 9.1.4.H.1., change as follows:
"1. Minimum weights for cars with normally aspirated piston engines will be determined by 1.1 lbs/cc displacement for the
installed engine (see following table) the following table. Displacement is the stock displacement for the installed engine. For the
purpose of weight assignment, engine displacement will be rounded to the nearest 50cc (e.g., 2176cc = 2200cc and 2175cc =
2150cc)."
Factory Engine Displacement (cc) Minimum Weight (lbs)

A specification table follows in the original; it is not shown here.

2022-03-01 STU Request to Remove A4 1.8t from STU Spec Line Tables

#31465 from Chip Herr · Rule change · TB 22-03 (2022-03 Fastrack)

In STU Spec Lines, Table B, Audi A4 Turbo, change as follows:
Model: "Audi A4/VW 1.8 Turbo"
Minimum Weight: "Chart 3050"
Notes: "K04 turbocharger permitted. IHI VF30 turbo with 35mm turbo inlet restrictor permitted required."
In STU Spec Lines, Table B, Porsche 944 Max Disp. 1800, change as follows:
Minimum Weight: "Chart 3050"
Notes: "VW/Audi 1.8L 35mm turbo engine permitted inlet restrictor required."

Applies to Audi A4 on this page: Chip Herr

2022-03-01 STU Improved Touring Tires

#32063 from Greg Amy · Rule change · TB 22-03 (2022-03 Fastrack)

In STU Table B, Improved Touring Vehicles (1985-), change Notes as follows:
"Must completely conform to ITCS requirements. Tires must conform to 9.1.4, Tires & Wheels"
In STL Table B, ITA-spec and ITS-spec RX7, change Notes as follows:
"Must completely conform to ITCS requirements. Tires must conform to 9.1.4, Tires & Wheels"
In STL Table B, ITS, ITA, ITB, or ITC vehicles (1985- ), change Notes as follows:
"Must completely conform to ITCS requirements. Tires must conform to 9.1.4, Tires & Wheels"

2022-04-01 STU Request Adjustment to Min Weight for STU BMW E36 M3 (95-99)

#31535 from Griffin Gamcsik-Uly · Rule change · TB 22-04 (2022-04 Fastrack)

In STU Spec Lines, BMW E36 M3 (95-99), change as follows:
Car: "BMW E36 M3 (95-99) S52B32"
Maximum Displacement: "3200 3152"
Weight: "3200 3110"
Notes: "Engines are permitted 0.040 overbore, 0.5 point increase in compression. Engines must use the OEM
camshaft lift and stock intake plenum. "

Applies to BMW M3 on this page: Michal Kuna, Zach Hillmann

2022-04-01 STU BMW E36 M3 Canadian (North American) S50B32 engine

#31866 from Ryan Hameetman · Rule change · TB 22-04 (2022-04 Fastrack)

In STU Spec Lines, BMW S50B32 Euro, classify as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
BMW S50B32 Euro 3201 3300 Engines are permitted 0.040 overbore, 0.5
point increase in compression. Engines
must use the OEM camshaft. Engine must
use stock intake plenum.

2022-04-01 STU Engine Swap Origin Country

#32209 from Jon McLendon · Rule change · TB 22-04 (2022-04 Fastrack)

In ST, GCR Section 9.1.41.G.2., change as follows:
Engines from vehicles not available in a car delivered in North America the United States will be considered and approved on a
case-by-case basis for use in ST. For an engine to be considered, a member must submit a classification request to the CRB with
the following information:

2022-04-01 STU CRX/Civic Del Sol

#32214 from Stephen Wheeler · Rule change · TB 22-04 (2022-04 Fastrack)

In STU, classify Honda CRX (84-91) as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Honda CRX (84-91) Chart Ineligible for front wheel drive weight
reductions.
In STU, classify Honda Civic Del Sol (93-97) as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Honda Civic Del Sol
(93-97)

2022-04-01 STU Error correction

#32383 from Super Touring Committee · Rule change · TB 22-04 (2022-04 Fastrack)

In STU, GCR Section 9.1.4.1.F.1, change as follows:
"Wheels may not exceed 18 inches in diameter and 8.0 inches in width for vehicles under 2950 lbs. base weight. Vehicles over
2951 with base weight equal to or over 2950 may use a 9 inch wide wheel."

2022-04-01 STU Single TB Weight Modifiers Add to Chart

#32393 from Club Racing Board · Rule change · TB 22-04 (2022-04 Fastrack)

Effective 5.1.2022 In STU, GCR Section 9.1.4.H.1., add to chart as follows:
Factory Engine Displacement (cc) Minimum Weight (lbs)
2450 2695 2596
2500 2750 2635
2550 2665 2675

2022-05-01 STU Opposed to the Proposed STU Weight Chart

#32381 from Edwin Soto-Quinones · Rule change · TB 22-05 (2022-04 Fastrack)

In STU, GCR Section 9.1.4.1.H, add the following after weight chart:
"Any STU car that qualified to run 9 inch wheels in 2021, may continue to run 9 inch wheels thru 2022 only."

2022-05-01 STU Clarification request for GCR 9.1.4.D.3.a Splitter Definition

#32414 from Bill Damron · Rule change · TB 22-05 (2022-04 Fastrack)

In ST Category Specifications, GCR Section 9.1.4.D.3.a, change as follows:
"Definition: A horizontal, single-plane aerodynamic device attached to the lower est point of the front of the vehicle, protruding
forward. It is intended to divert air and produce downforce through vertical pressure differential. A splitter shall have no vertical
deviations."

2022-07-01 STU Error in new minimum weight table when combined with other text

#32711 from Super Touring Committee · Rule change · TB 22-07 (2022-07 Fastrack)

In STU Specifications, GCR Section 9.1.4.1.H., eliminate the following in its entirety and renumber:
"2. Normally-aspirated engines with stock displacement 2976cc-3200cc that breathe through a single throttle body may reduce
base engine weight 10%."

2022-07-01 STU Redundant Language in May GCR

#32713 from Super Touring Committee · Rule change · TB 22-07 (2022-07 Fastrack)

In ST, GCR Section 9.1.4.G.29, change as follows:
"Any engine balance shafts and associated gears or pulleys may be removed and the resulting openings plugged (including those
in oil passages). Alternate pulleys or gears, of the same number as stock, may be installed in the location of the balance shaft
pulleys or gears if required for timing belt or chain operation; they must serve no other purpose. Any engine balance shafts and
associated gears or pulleys may be removed and the resulting openings plugged (including those in oil passages). Alternate
pulleys or gears, of the same number as stock, may be installed in the location of the balance shaft pulleys or gears if required
for timing belt or chain operation; they must serve no other purpose."

2022-08-01 STU Request Mazda 13 B turbo

#32668 from Raymond Philibert · Rule change · TB 22-08 (2022-08 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Allowance, classify Mazda 13 B Turbo as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Mazda 13B Turbo N/A Chart Limited to Streetport only. Stock turbos are
not allowed; only alternative turbos listed
in the STU rules are allowed.

2022-08-01 STU Hood Vents and Intercooler Scoops

#32733 from Patrick Lipsinic · Rule change · TB 22-08 (2022-08 Fastrack)

In STU, GCR section 9.1.4.1.A.2., add as follows:
"Louver vents that are OEM do not count in the number of vents allowed or 200 square inch allowance."

2022-08-01 STU Non 4 valve weight reduction removed

#32808 from Bjorn Stange · Rule change · TB 22-08 (2022-08 Fastrack)

In STU Specifications, GCR Section 9.1.4.1.H.1., change Chart as follows:
"Factory Engine Displacement (cc) - 2400
Minimum Weight (lbs) - 2596 2595"
In STU Specifications, GCR Section 9.1.4.1.H.1., add the following:
"Normally-aspirated engines of fewer than 4 valves per cylinder may reduce base engine weight 9%."
In STU Specifications, GCR Section 9.1.4.1.H., remove the following and renumber:
"4. All Direct Injected (DI) Turbocharged engines will be limited in preparation. DI Turbo engines must use OEM compression
ratios, OEM camshaft lift, and may not port the cylinder head."

2023-03-01 STU E&O STU NA Weight Chart.

#33737 from Eric Heinrich · Rule change · TB 23-03 (2023-03 Fastrack)

In STU, GCR Section 9.1.4.1.H.1. chart, Factory Engine Displacement (cc) Minimum Weight (lbs), change as follows:
"2450 2596 2595"
"2600 2860 2710"

2023-04-01 STU Alternate OEM Miata Intake Manifold

#33827 from Brandon Steinhauer · Rule change · TB 23-04 (2023-04 Fastrack)

In STU Spec lines, classify Mazda BP5A as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Mazda BP5A 1839 Chart May use engine in its entirety or specific
components from the engine.

2023-07-01 STU 2022 Toyota GR Cup for STU

#34449 from Club Racing Board · Rule change · TB 23-06 (2023-05 Fastrack)

In STU Spec Lines, Toyota GR Cup (2022-), classify as follows:

A specification table follows in the original; it is not shown here.

2024-02-01 STU ST Electric-Assisted Steering Systems

#35066 from Jose Osiris Pena · Rule change · TB 24-02 (2024-01 Fastrack)

In GCR, Section 9.1.4.M.16., change as follows:
"Power steering may be modified in any of the following ways:
a. disconnected , pump, belt, pulley, and hoses may be removed. Hoses may also be looped. Steering rack or box may be
modified internally to work without pump.
b. an OEM manual steering rack for that model may be fitted
c. an electric power steering pump may be fitted
d. an OEM electric-assisted steering system may be used or any column mounted electric steering assist may be used
e. an OEM hydraulic-assisted steering system may be used"

2024-03-01 STU Letter #35397 addendum

#35453 from Aaron Fitzsimmons · Rule change · TB 24-03 (2024-03 Fastrack)

In STU Spec Lines, Mini Cooper S SC with Minimum Weight 1900 and 2100, add to Notes:
"Alternate LEAP OMICRON hood scoop part # LEP-OMICRON3 is permitted."

2024-03-01 STU S54 Drysump

#35464 from Macey Urso · Rule change · TB 24-03 (2024-03 Fastrack)

In STU Spec Lines, BMW S54 B32 OEM, add to Notes as follows:
"Dry Sump oiling system permitted."

2024-08-01 STU RWD Turbo Disadvantage

#36255 from David Fiorelli · Rule change · TB 24-08 (2024-08 Fastrack)

In GCR, Section 9.1.4.1.H.3 - Inlet Restrictor (mm) Minimum Weight (lbs) table, change as follows:
"RWD cars must reduce restrictor 1 mm from this table"

2024-11-01 STU R53 15% Pulley Request

#36980 from Aaron Fitzsimmons · Rule change · TB 24-11 (2024-11 Fastrack)

In STU Spec Lines, Mini Cooper S SC, add to notes:
1900: "Stock supercharger pulley. 2.565 diameter."
2100: "JCW Pulley permitted. May run a 2.285 diameter pulley."

Applies to Mini Cooper S on this page: Tony Lechner

2024-12-01 STU Request to Remove Miata Hubs from General category

#37138 from Christopher Childs · Rule change · TB 24-12 (2024-12 Fastrack)

In GCR, Section 9.1.4.M.18., change as follows:
"18. Allow alternate front wheel front hubs, Mazda Motorsports Development Part #0000-04-5HUB-S1, for the 90-05 Mazda
Miata: Mazda Motorsports Development Part #0000-04-5HUB-S1."

2024-12-01 STU BMW N54/N55 Engine Allowance

#37146 from Martin Sarukhanyan · Rule change · TB 24-12 (2024-12 Fastrack)

"Turbo inlet restrictors designed per GCR Appendix F Technical Glossary definition of “Turbo Inlet Restrictor” may be required;
see table 9.1.4.1.H.h.2 3. Swapping of turbochargers between engine makes and models is prohibited. Supercharged cars may be
approved on a case-by-case basis; twin turbo engines are allowed on a case-by-case basis only. Contact the Road Racing
Technical Office for details. Twin turbo engines may be converted to single turbo using one of the allowed alternate turbos (see
9.1.4.1.H.3 2). Aftermarket turbocharger and supercharger kits will be allowed on a case-by-case basis.

2025-01-01 STU Audi 1.8t Wagon STU Table B

#36685 from Mike McLaughlin · Rule change · TB 25-01 (2025-01 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Requirements, delete Audi/VW 1.8 Turbo in its entirety.
In STU Spec Lines, Table B: Alternate Vehicle and Engine Requirements, Porsche 944 w/Max Displacement 1800, change as
follows:
Weight: "3050 Chart"
Notes: "VW/Audi 1.8L 35mm turbo engine permittedinlet restrictor required."

2025-01-01 STU Merger GT3 to STU

#37486 from Club Racing Board · Rule change · TB 25-01 (2025-01 Fastrack)

In STU, Table C, change STU-GT3 charge as follows:
"(Effective January 1, 2026) TABLE C: STU-GT3U"

2025-01-01 STU GT3 TCR Tire allowance

#37494 from Club Racing Board · Rule change · TB 25-01 (2025-01 Fastrack)

In STU, Table C, GT3 TCR, add to Notes the following:
"May run DOT approved tire with maximum section width of 275 with 100 pound weight adder. May not run A compound with
275."

2025-03-01 STU BMW N54/N55 Engine Allowance Follow Up

#37447 from Martin Sarukhanyan · Rule change · TB 25-03 (2025-03 Fastrack)

In STU Spec Lines, Table A, classify BMW N54/N55 as follows:
STU Maximum Displacement
(cc's) Minimum Weight Notes
BMW N54/N55 3.0 Chart +3% (DI) Short blocks, heads, and intakes may be
freely swapped within these engine
designations. N54 twin turbo not allowed

2025-03-01 STU STU Mini Cooper pulley size clarification re: letter #36980

#37717 from Aaron Fitzsimmons · Rule change · TB 25-03 (2025-03 Fastrack)

In STU Spec Lines, Mini Cooper S SC, add to notes:
2100: "May run a 2.285 2.185 diameter pulley."

Applies to Mini Cooper S on this page: Tony Lechner

2025-03-01 STU Question About a Weight Modifier

#37782 from Peter St Pierre · Rule change · TB 25-03 (2025-03 Fastrack)

In STU Spec Lines, Table A, Honda K20C1 Turbo I4, add to Notes the following:
"The 3% DI weight adder does not need to be applied."

2025-03-01 STU Increase Minimum Weight

#37919 from Club Racing Board · Rule change · TB 25-03 (2025-03 Fastrack)

In STU Spec Lines, Table C: STU-GT3U, change Minimum Weight as follows:
"150 250 pounds"

2025-05-01 STU Wheel Size Inconsistency

#38018 from David Fiorelli · Rule change · TB 25-05 (2025-05 Fastrack)

In GCR, Section 9.1.4.1.F.1., change as follows:
"Wheels may not exceed 18 inches in diameter. or 8.0 inches in width for vehicles 2950 lbs. and under minimum allowed race
weight. Vehicles over 2850 minimum allowed race weight may use a 9 inch wide wheel. Cars equal to or less than 2,850 lbs.
minimum allowed race weight may not use wheels wider than 8 inches. Cars greater than 2,850 lbs. minimum allowed race
weight may not use wheels wider than 9 inches."

2025-05-01 STU Table C: STU-GT3U Clarification

#38268 from Club Racing Board · Rule change · TB 25-05 (2025-05 Fastrack)

In STU Spec Line, Table C: STU-GT3U, change as follows:
Minimum Weight: “Current GT3 race weight plus 250 225 pounds”
Notes: "DOT approved tire with maximum section width of 245. GT3 cars base wheel is a maximum of 15”x9”. 18”x9” wheels
allowd with a 3% weight addition. GT3 cars utilizing 15”x7” wheels are limited to a maximum section width of 225 with a 25
pound weight reduction"
"All GT3U (Majors and Runoffs) cars using up to 15"x7" wheels limited to 225 section width tires shall run at current GT3 race
weight plus 225lbs. All Gt3U cars shall run a DOT approved tire with a maximum section width of 245. GT3U cars are allowed
optional 15"x9" wheels with a 1.5% weight addition or up to 18"x9" wheels with a 3.0% weight addition to the total weight

2025-07-01 STU 2.8-3.2L N/A Engine Allowances

#38007 from Ben Slechta · Rule change · TB 25-07 (2025-07 Fastrack)

In GCR, Section 9.1.4.G.1, add the following:
"A maximum section width of 245 is permitted. Cars over 3150 lbs. may run a 275 tire with a 2% weight adder."

2025-07-01 STU 2006-2015 Mazda Miata Intake Manifold

#38422 from German Candelario Candelario · Rule change · TB 25-07 (2025-07 Fastrack)

In STU, Table A, Mazda MZR (LF, L3, L5), change Notes as follows:
"May use Goodwin Part # 61-2510 or Gato Performance Part #31972 Intake manifold . "

2025-07-01 STU Requesting Approval of the JDM Honda h23a

#38489 from Eric Fiest · Rule change · TB 25-07 (2025-07 Fastrack)

In STU, Table B, classify Honda JDM H23a as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Honda JDM H23a 2259 Chart Must meet all ST engine regulations.

2025-08-01 STU STU-TCR Adjustments

#38723 from Club Racing Board · Rule change · TB 25-08 (2025-08 Fastrack)

In STU Spec Lines, Table C: STU-GT3U, GT3-TCR, change as follows: Remove the current TCR spec line and add the TCR spec lines
from GT3 that are being removed, adding the below to the notes.
"DOT approved tire with maximum section width of 245. May run DOT approved tire with maximum section width of 275 with
100 150 pound weight adder. May not run A-compound with 275. STU-TCR spitters and side valance must comply with
9.1.4.D.3.f. STU-TCR chassis ride height must comply with 9.1.4.1.A.1."

2025-08-01 STU Lotus Weight Reduction

#38772 from Club Racing Board · Rule change · TB 25-08 (2025-08 Fastrack)

In 9.1.2. GT2/ST Spec Lines, Lotus Evora GT4, change Weight as follows:
"2750 2700"
In STU Table B: Alternate Vehicle and Engine Allowances, change Weight as follows:
Lotus Elise Cup R: "2300 2250"
Lotus Elise SC/ Lotus Exige SC: "2300 2550
2500 2450"

2025-09-01 STU Lotus Weight Reduction E&O

#38919 from Club Racing Board · Rule change · TB 25-09 (2025-09 Fastrack)

In STU Table B: Alternate Vehicle and Engine Allowances, change Weight as follows:
Lotus Elise SC/ Lotus Exige SC: "2450 2250"

2025-11-01 STU Non-Homologated Engine Swaps - Specifically K24A2 w/ Honda CRZ

#38746 from William Rori · Rule change · TB 25-09 (2025-09 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Allowances, Honda K24, change Weight as follows:
"(Effective 11/1/2025) Chart + 2%"

2025-12-01 STU Turbo Inlet Restrictor Table

#38961 from John Weisberg · Rule change · TB 25-12 (2025-12 Fastrack)

In GCR, Section 9.1.4.H.3, change chart as follows:

A specification table follows in the original; it is not shown here.

2025-12-01 STU 275 Tire Rule

#38983 from Peter Federlin · Rule change · TB 25-12 (2025-12 Fastrack)

In GCR, Section 9.1.4.G.1., change as follows:
"A maximum section width of 245 is permitted. Cars over 3150 lbs. may run a 275 tire with a 2% weight adder."

2025-12-01 STU STU Honda Engine weight penalty

#39375 from Super Touring Committee · Rule change · TB 25-12 (2025-12 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Allowances, change Minimum Weight as follows:
Honda K20: "Chart + 2%"
Honda K24: "Chart + 2%"

2026-01-01 STU Request for Permission on Aftermarket Turbo Kit and Intake

#39529 from John Grim · Rule change · TB 26-01 (2026-01 Fastrack)

In STU Spec Lines, Table A: Alternate Vehicle and Engine Allowances, Mazda MZR (LF, L3, L5), change Notes as follows:
"Short blocks, heads, and intakes may be freely swapped within these engine designations. May use Goodwin Part # 61-
2510 or, Gato Performance Part #31972 or Jack Spania Racing 70 mm sheet-metal aluminum Intake manifold. Must use stock
throttle body or Acura part number 16400-PND-A17."
In STU Spec Lines, Table A: Alternate Vehicle and Engine Allowances, classify Mazda MZR (LF, L3, L5) Turbo as follows:
STU Maximum Displacement (cc's) Minimum Weight Notes
Mazda MZR (LF, L3,
L5) Turbo

2026-03-01 STU Fab 9 Racing Intake Manifold in STU

#39767 from Marc Hoover · Rule change · TB 26-03 (2026-03 Fastrack)

In STU Spec Lines, Table A: Alternate Vehicle and Engine Requirements, Mazda MZR (LF, L3, L5), add to Notes as follows:
"Short blocks, heads, and intakes may be freely swapped within these engine designations. May use Goodwin Part # 61-2510,
Gato Performance Part #31972, or Jack Spania Racing 70 mm sheet-metal aluminum or Fab 9 Elite NC MX5 Performance Intake
manifold. Must use stock throttle body or Acura part number 16400-PND-A17."

2026-04-01 STU Mazda Rx-8 Renesis - Streetported Variant & Added Weight

#39785 from Kyle Bolden · Rule change · TB 26-04 (2026-04 Fastrack)

In STU Table B: Alternate Vehicle and Engine Allowances, add the following:
Model: "Mazda Renesis Street Port"
Maximum Displacement (cc's): "N/A"
Minimum Weight: "2450"
Notes: "Street porting allowed. Alternate 70mm choke throttle body from the following list allowed: OE from 1996- 2004
Mustang 4.6 liter V8; BBK #1700 (e.g., Summit #BBK-1700); Summit #227204; Trickflow #24070 1” thickness max manifold
adapter allowed."

2026-04-01 STU Eliminate 33 and 34 mm TIRs

#39872 from Super Touring Committee · Rule change · TB 26-04 (2026-04 Fastrack)

In STU, GCR Section 9.1.4.H.3., change chart as follows:
Inlet Restrictor (mm): "33"
Minimum Weight (lbs): "2380"
Inlet Restrictor (mm): "34"
Minimum Weight (lbs): "2525"

2026-05-01 STU Turbo Restrictor Size Increase Request

#40008 from Peter St Pierre · Rule change · TB 26-05 (2026-05 Fastrack)

In STU Spec Lines, Table A: Alternate Vehicle and Engine Requirements, Honda K20C1 Turbo I4, change Notes as follows:
"35 36mm TIR required."

2026-05-01 STU GT86 Cups Car in STU

#40028 from Peter Federlin · Rule change · TB 26-05 (2026-05 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Allowances, change Notes as follows:
"Must meet all 2022 Toyota GR Cup rules, including tires or DOT tires conforming to section 9.1.4.O with a maximum section

A specification table follows in the original; it is not shown here.

2026-06-01 STU Request to allow BMW M50B20TU engine in STU

#40202 from Bjorn Stange · Rule change · TB 26-06 (2026-06 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Requirements, classify the following:
Make: "BMW M50B20TU"
Maximum Displacement: "1991"
Minimum Weight: "Chart"
Notes: "Must meet all STU engine regulations."

2026-06-01 STU Calculating Weight

#40224 from David Wessel · Rule change · TB 26-06 (2026-06 Fastrack)

In GCR, Section 9.1.4.1.H.6., change as follows:
"The minimum weight is determined by the installed engine displacement, TIR or table spec line. It is to be used as the base
weight for any chassis weight related adjustments. Chassis related All positive adjustments that are percentage based are
performed by adding the total of all specified percentages first and subtracting the total of all negative specified
percentages second if necessar y. Final step is addition or subtraction of specified weight in pounds."
In GCR, Section 9.1.4.2.H.4., change as follows:
"The minimum weight is determined by the installed engine displacement or table spec line. It is to be used as the base weight
for any chassis weight related adjustments. Chassis related All positive adjustments that are percentage based are performed by

2026-07-01 STU 9” Wheels

#40433 from John Weisberg · Rule change · TB 26-07 (2026-07 Fastrack)

In GCR, Section 9.1.4.1.F.1., change as follows:
"Wheels may not exceed 18 inches in diameter. Cars equal to or less than 2,850 2,825 lbs. minimum allowed race weight may not
use wheels wider than 8 inches. Cars greater than 2,850 2,825 lbs. minimum allowed race weight may not use wheels wider than
9 inches."

2026-07-01 STU Weight adjustment to former GT3U cars

#40474 from Super Touring Committee · Rule change · TB 26-07 (2026-07 Fastrack)

In STU Spec Lines, STU-GT3U, GT3U, change Minimum Weight as follows:
"Current GT3 race weight plus 225 275 pounds"
In STU Spec Lines, STU-GT3U, GT3U, change Notes as follows:
"All GT3U (Majors and Runoffs) cars using up to 15”x7” wheels limited to 225 section width tires shall run at current GT3 race
weight plus 225 275lbs. All Gt3U cars shall run a DOT approved tire with a maximum section width of 245. GT3U cars are allowed
optional 15”x9” wheels with a 1.5% weight addition or up to 18”x9” wheels with a 3.0% weight addition to the total weight
including the 225 275lbs Increase the minimum weight of all GT3/GT3U 2.0 liter unrestricted engines to +75 lbs. All GT3 cars
running in STU must meet the minimum ride height of 3.0” for the main frame rails not including rub blocks and a 2” minimum

2026-09-01 STU Wheel and tire requirements for GT3U

#40679 from Robert Maples · Rule change · TB 26-09 (2026-09 Fastrack)

In STU Spec Lines, Table B: Alternate Vehicle and Engine Allowances, STU-GT3U, change Notes as follows:
"All GT3U (Majors and Runoffs) cars using up to 15”x7” wheels limited to 225 section width tires shall run at current GT3 race
weight plus 275lbs. All Gt3U cars shall run a DOT approved tire with a maximum section width of 245. GT3U cars are allowed
optional 15”x9” wheels with a 1.5% weight addition or up to 18”x9” wheels with a 3.0% weight addition to the total weight
including the 275 lbs Increase the minimum weight of all GT3/GT3U 2.0 liter unrestricted engines to +75 lbs. All GT3 cars running
in STU must meet the minimum ride height of 3.0” for the main frame rails not including rub blocks and a 2” minimum for the
front spoiler and splitter.
1. Wheel and tire requirements for GT3U

A specification table follows in the original; it is not shown here.