[Gunner]

I'll clarify my comment - which I thought was self-explanatory, but some valid points have been raised.

If we had unlimited tire choices for these cars, I'd never say anything as absolute as "wider is always better." But our choices for original-spec tires have dwindled until finding adequate 15-inchers is a chore, and no really good options remain. If an owner wants to go to 17-inch wheels and not mind the variation/distortion in looks, there are scads of tires to choose from and a set more closely coupled in size would have benefits on both street and track.

If you're in the group leaning towards originality and you want to stay with 15s, I don't think there's any question that the widest tires you can find and fit on the back are what you want. Less for handling than to try and safely hook 400-600 HP to the ground in the hands of a driver with (likely) little or no race experience. Getting as much meat up front to correspond is the logical followthrough.

Experienced track or autocrosser? 17s okay? One set of rules.

Average Cobra driver? 15s mandatory? Different set of rules, beginning with "wider is better."