Rim width for autocross. 225/45/15 (f) 275/35/15 (r)
 

What would be the proper width for a 225 and 275 Hoosier A6 tire for autocross?

According to Tire rack, on a 15" rim, 8" and 10" respectively.
http://www.tirerack.com/tires/Spec.j...irePageLocQty=

Didn't Grass Roots just run some 275's on an 8 inch RX-8 wheel for their last tire test? It was something way bigger than I thought could fit.

Speaking in auto-x terms, for the 225 an 8" rim would be great but you could easily go up to a 9" (Hoosiers run much wider than their marketing dimensions suggest). Most folks are running that 275/35 on a 10" rim, but a 10.5" or 11" would maximize the tire width.

Yes, they did.

And one very interesting result from that was that they had to use 245 v710's, as the 275 v710's simply would not fit on an 8 inch wheel.

And the v710's were STILL faster and easier to drive than all the other tires in 275.

Actually it was 285's and 295's. They suggested that it was the better gearing from the shorter tire and better transitional response that made the 245's faster, as they did have slightly less grip.

They were doing this for stock class. For any other class where you're allowed any width wheel you should go for a wider wheel as it'll improve responses and put more rubber on the road for more grip.

Good point. My single turbo car will be running 265/45/16's. Lower profile and wider rubber would be nice, but the budget is not going to allow for new wheels for a while yet.