wordingGT3U wheel and tyre options clarified: 15x7 with 225 section at +275 lbs; 15x9 with 245 section at +275 lbs plus 1.5%; 16–18x9 with 245 section at +275 lbs plus 3.0%.As printed in 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. 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.
faster · weightSTU-GT3U minimum weight reduced from plus 250 to plus 225 pounds; wheel and tyre options clarified with weight adjustments.As printed in 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 including the 225 lbs."
faster · weightSTU-GT3U allows all current STU cars except TCR cars to reduce weight by 4% after other modifiers.As printed in Fastrack
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"
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."