Hey guys.

I have done a ton of reading under searches regarding tire size, but I am not finding the definitive information I need.

As most of you know, I have flares on my car and can accomodate 285-30-18s.

I currently Auto-X in DSP at approximately 2800 lbs + me + passenger = approximately 3100lbs.

Next year I will be Auto-Xing in FP at approximately 2500lbs + me = 2650lbs.

I will also be doing a ton of DEs and some competitive Solo 1 (time trials). I'd like to get rid of the flares and run 245-40-17 Hankooks in both compounds (soft for autox and medium for track days). My question is for the time trials/DE/track use, should I be using 285s since I can fit them or is the size a waste due to my stock motor 328? And for Auto-X use is it likely that due to the significantly reduced weight, I can get decent performance out of 245s?

Let me put it to you this way. We run 245 fronts, and 285 rears in our 2250 lb (with driver) car, and we get heat into the tires for autocrossing.

At 2650, I'd still run the 285s for autocross. I'll let the track people speak more about the track performance.

Ok thats cool.

Another thing I should mention is I'm from Vancouver, BC. I can count on one hand the number of time it went over 80F last summer. We autox all year around. In spring and fall, I could barely get those tires warm even with a co-driver, let alone to optimal heat. In the summer, I couldnt overheat them if I tried except at one event, the hottest event of the entire year which was maybe 85F with 2 drivers.

Our setup worked at Nationals, which was probably in the mid to high 60's when XP ran. They did take a run to get warm, but after that, they worked, and worked well. (I believe I had the 3rd quickest scratch time on the west course this year of anything with fenders)

The year before, in the 50's, the 285 front, 335 rear setup did NOT work. Pyro showed temps after 6 runs (both drivers) still under 90 degrees. And the car was heavier then too.

ok, fair enough. so i have to keep the 285s to win.

probably an unfair loaded question, but any idea how much slower going to 245s would be?