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I ran a new set of 235/45/17 RE-71R's yesterday on my '14 BRZ at our local autocross. I had a set of 225/45/17 Dunlop SSII tires on the car most of the year. The Dunlops worked great on tracks for lapping days but they were lacking grip for autocrosses. I thought I would try a larger size so I bought the Bridgestones. Grip was fantastic and car felt neutral to slightly loose but I do the 'pedal dance' and prefer a 'loose' set up for autocrossing.
I know I gave up some gearing with the taller tires, and there is some weight increase as well, along with a higher center-of-gravity. I thought I might offset the disadvantages with a larger footprint and grippier tires.
I don't think I was even close to the limits of adhesion in the sweepers but I did notice the tires rolling over onto sidewalls. I started out with 32 psi in the rear and 35 in the front. I decided to bump up the air pressure about two pounds in the back and four in the front. But I didnt really notice any improvement in handling. I am now wondering if I was going backwards with tire pressures trying to improve the handling? I have always tried to reduce amount of rollover with higher pressures but now I am wondering if I am actually decreasing the amount of grip since a higher pressure reduces size of 'footprint'.
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