I think wide 15" wheels don't fit because of the tie-rod ball joint.
http://www.ft86club.com/forums/showp...1&postcount=19
http://www.ft86club.com/forums/showt...836#post495836
(I thought about running 16" wheels but the 17" wheel rim tire combination actually produced the smallest diameter in a reasonable tire size).

I guess I should pay more attention. Thanks for the heads up.

What's "best" has too many variables to provide a definitive answer; even for just autocross. The ideal tire width depends on the class you're shooting for and the rules of that class. Certain classes have wheel width limitations which in-turn affect what would be the ideal tire width. This is further complicated by the performance category and brand of tire you use.

If you have more specifics about what your racing plans/goals are and the classes you're looking to run, it might be easier for us to give you advice along those lines.

Running 215 Michelin PSS (stock suspension and engine) and I feel like it's not enough tire. I'll probably try running a 225 or 235 next.

Can anyone chime in running a 225 and 235 tire on the OEM wheels? Does the 235 tire fit at all?

When you say it's not enough tire, is this for HPDE, AutoX, or just street driving? Also, in your consideration for a wider tire, are you wishing to stick with Michelin PSS? A 225 or 235 tire will fit on a 7" wheel fine, but whether it provides better performance will depend on the brand/model and driving application.

80% HPDE, 20% street. pretty much only street miles are to/from events. After driving on PSSs, RS3s, Star Specs, RA1s, R888s, AD08s, NT05s, NT01s as far as "streetable" track tires, I have actually come to like the PSS the best overall for the various track conditions we get down here in FL. I do about 10-14 HPDE events a year with the BRZ, and SCCA regional club races with a Miata.

PSS is certainly a great tire. I run 215/45/17 for daily driving and rainy autocrosses and love them (I like Rivals and RS3s for dry). The sidewalls of the PSS are stiff enough to handle using a 225 on stock sized wheels, but I wouldn't go wider than that.

Just picked up a set of 17x9 et38 for a killer deal ($350 shipped brand new from discount tire direct) and will be testing out a 245 PSS in the near future with it, and will report back.

For SCCA Street class, would you run 16x7 or 17x7 light wheels, and with what width tire?

The easy answer is just to run 17x7 wheels and 225/45/17 tires. Pretty much all the "extreme" and "max" performance tires come in this size, so you will have plenty of options to choose from.

Alternatively, you could run 16x7 wheels and 225/50/16 tires. Again, most tires in the "extreme" and "max" performance categories come in this size as well. Generally speaking 16" wheels and tires are cheaper, so that is a plus, but a 50 sidewall tire might feel a little sloppy and not transition as quickly as a 45 sidewall tire.

There are a few other sizes you could consider depending on the tire brand/model you choose (like 225/45/16 or 235/40/17), but a 225/45/17 or 225/50/16 will give you the most options.

My wheel spec is 18x9.5 +40mm offset for all wheels. Rays Gramlights 57Xtreme. Tires 255/35-18 Pirelli P Zero.

I have done some research but didn't find a definitive answer for the best setup for track days and need some advice to choose the most suitable width for front and rear. I'm also planning to get semi-slick tires.

If I go for narrower front at 235 is it going to be more nimble and reduce roll resistance? For the rear I'm planing to keep the 255 width for more grip.

Need advice on this please.

I'm trying to on a proper tire size for track use on a Vortech supercharged frs. I see many people have gone 17x9 with 245 width, but then again I see some people suggesting a narrower tire/rims for better times.
In short, i currently only have budget for a new set of rims and tires for track use but would like to get the proper size for a FI application, anyone out there that can offer some insight? Thanks!