Originally Posted by X-VWGLX
using stoCk 16" rims, OVERSIZING was a mistake. I moved from stock size 205/55-16 712's to a wider 225/50-16 MX, and my lap times INCREASED by 3 sec per lap. the oversized tire was less stable in high speed cornering, as the car wallowed over the larger sidewalls. I never would have guessed that the wider tires would suck more, even though they are better design and stickier compound.
If you never go to the track, oversizing will not matter. but 6 hours with the new, oversized MX's at 4 track days, and i still havent matched the lap times acheived with stock sized 712's. thats as scientific proof as i have ever seen against oversizing. I even added a COBB stage 1 and cant catch my old lap times!!!
My next set of track meat will be SMALLER 205's on stock rims. it looks worse, but performs better.
Wow. Considering how crappy 712's are (and how grippy MX's are), I think there's something else going on to make you that much slower.
Given, oversizing might be screwing up your steering feel and possibly your turn in, but there's no way it's making you that much slower by going to a tire which is much stickier.