[OfficeLinebacker]

I think that the main issue is heat dissipation. There's not much rubber to absorb the heat, that's the limiting factor when it comes to speed ratings, is heat dissipation and resistance.

That, and the width of the tread is like half the stock width. The thing is smaller so it turns faster at any given speed so you can assume the tread life, is less than half. Add in that it's not designed to last and make your own assumptions.

That all said, we all know of cars we've seen where the people have driven around on the spare for weeks with no ill effects other than to their reputation. Also, I am sure different brands of rubber and different manuf. of rims make a big difference. The ones I picked out are Firestones, which have a reputation for great tread life.

I also admit that I wonder just how bad the car would oversteer with the donuts on the rear. Given that the car pushes like a dump truck in stock trim, and has a rear sway bar about the diameter of a #2 pencil, it'd be fun to drift with it. Of course that's completely counter to what we're trying to accomplish here, but I am a contrarian among contrarians. Don't flame me!