These are the stock 17" twists. What's the largest size tires I can put on my wheels. I'm thinking 225/45-17 on the front and 255/40-17 on the rear.

???

 

Yes, you can install a 225 on the front 7" wheels. However, its effectiveness would be questionable. The ideal wheel width for that size tire is 7.5".

 

NickS - I went through the same eval for R-compound tires about a month ago and chose to go with the stock size 205/50 and 255/40 combo due to limited availability in the 225/45 size. I was looking for a tire I could drive to the track on safely. The only options in the 225/45 size for the front with corresponding matched rear tire are the V700s, Pirelli Corsa, and MPSCs. However, MPSCs are spec'd at a minimum rim width of 7.5"s, the Pirelli's are on back order for months and the V700s aren't ideal for driving back and forth to the track on.

I ended up going with Toyo RA-1s and have been pretty happy. It was my first set of R-compound tires and they break away fairly linearly and actually squeel at the limit which most r-compounds do not.

While the adhesion limit goes up significantly, the car retains its heavy understeer bias with the stock sizes. To dial this out I believe you need a larger front tire -- but on wider than factory rims. I got a more agressive alignment with -0.6 negative camber (most they could get out of stock suspension) that helped a little but the car still understeers heavily. Next step for me is 18-8.5" wheels with a 235 or 245 front tires. It would be great to hear from others that have been able to dial out the understeer bias.