GT3U (GT-3U) combined into STU, removed from GRAND TOURING (letter #39862)
Wording removed by a change is shown struck through, as in the original. 4 changes, 4 other letters.
Changes made
Wheel and tire requirements for GT3U
#40679 from Robert Maples · Rule change · TB 26-09 (2026-09 Fastrack)
neutralGT3U wheel and tire requirements reorganized; 15×7 225 section at GT3 weight plus 275 lbs; 15×9 245 section at plus 275 lbs plus 1.5%; 16–18×9 245 section at plus 275 lbs plus 3.0%.
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
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a. Cars using up to 15”x7” wheels and up to a 225 section width DOT approved tires shall run at current GT3 race weight plus 275lbs. b. Cars using 15”x9” wheels and 245 section width DOT approved tires shall run at current GT3 race weight plus 275 lbs plus 1.5%. c. Cars using 16, 17, 18” x9” wheels and 245 section width DOT approved tires shall run at current GT3 race weight plus 275 lbs plus 3.0%. 2. The minimum weight of all GT3/GT3U 2.0 liter unrestricted engines plus 275lbs, plus 75lbs. 3. 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."
A specification table follows in the original; it is not shown here.
Table C: STU-GT3U Clarification
#38268 from Club Racing Board · Rule change · TB 25-05 (2025-05 Fastrack)
fasterSTU Spec Line GT3U minimum weight reduced from plus 250 to plus 225 pounds; wheel and tire options clarified with weight adjustments.
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
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including the 225 lbs."
TCR Rulesets
#37981 from Club Racing Board · Rule change · TB 25-04 (2025-04 Fastrack)
fasterSTU-GT3U non-TCR cars may reduce weight by 4% after all other modifiers.
In STU-GT3U Spec Lines, Table C, add the following: "Table C: STU-GT3U Refer to section 9.1.2." In GCR, Section 9.1.4.H.7, change as follows: "All current STU cars, except TCR cars, may reduce their weight by 4% after all other modifiers"
Increase Minimum Weight
#37919 from Club Racing Board · Rule change · TB 25-03 (2025-03 Fastrack)
slowerSTU GT3U minimum weight increases 150 to 250 pounds.
In STU Spec Lines, Table C: STU-GT3U, change Minimum Weight as follows: "150 250 pounds"
Other letters
Weight Adjustment
#40556 from Armen Megregian · Not recommended · Minutes (2026-10 Fastrack)
If you run the car in STU we will continue to collect data and make changes when appropriate.
GT3/GT3U Rule Changes
#39258 from Grand Touring Committee · Recommended to the Board · Minutes (2025-12 Fastrack)
In GCR, Section 9.1.2.F.3., add the following: "10. Increase the minimum weight of all GT3/GT3U 2.0 liter unrestricted engines to +75 lbs. 11. Add a ride height minimum limit (for all GT3 rule set cars running in STU starting January 01, 2026) of 3.0" minimum including front spoiler and splitter."
Wheel Size Clarification
#38114 from Chris Edens · Taken care of · Minutes (2025-06 Fastrack)
Thank you for your letter. Please see letter #38268 in May 2025 Fastrack.
Competition Adjustments
#38024 from Warren Montague · Taken care of · Minutes (2025-06 Fastrack)
Thank you for your letter. Please see letter #38268 in May 2025 Fastrack.