GT3 +1mm SIR add 175lbs. In
#36098 from Grand Touring Committee · Rule change · TB 24-06 (2024-06 Fastrack)
GCR, Section 9.1.2.F.7. add the following:
"m. GT3 Rules Concerning Alternate Weights and SIRs.
1. Traditional GT3 cars that that are currently required to run an SIR may run +1mm above spec line listed size size with a 175lb.
weight penalty.
2. Competitors running the alternate SIR must display "+1.mm" on the side of their car next to the new weight."