After running two Autocrosses with my 205-55-16 (440 treadwear) tires I wanted a new setup. This is what I am going with: 16x7 RS wheels and Hankook Ventus rs2 Z212 (why are some tire names obnoxiously long?) size 225-45-16. This upgrade will accomplish several things: 1. Stickier Tires 2. Wider contact patch 3. This will make my overall diameter about 1" less. I know this will effectively lower my gear ratios and lower the car about .5". I KNOW this will mess with the odometer and speedometer, however these tires will be for AutoX ONLY! After I wear them in a little, of course So my question is this: I want my car in STS, and I read through the SCCA rulebook for AutoX classing. I couldn't find any restrictions on tire size other than treadwidth. Is this going to be legal for STS class? And will it be beneficial for AutoX?
7.5" rim width is the limit for STS 8 for STX No limit on rims for STU. Tyre: 225 STS 245 STX 245 for AWD in STU 275 for FWD/RWD in STU You are good for STS. The 1 inch diameter change will not be a large enough change to worry about speedo readings for street use.