15x7 Wheel/Tire Question
 

I recently bought some 15x7 wheels to serve as my dedicated autox/track wheels, and now I'm trying to see what tire size I should get for it. I've narrowed it down to 195/50/15, 205/50/15 and 225/45/15. I know a lot of ITS guys use 225/45/15, but I realize that the tire would look bubbly and bulged out on the wheel, to the detriment of sidewall stiffness. What do you guys think would be the best tire size?

195s are too narrow for 15x7. 225/45r15 fit fine and are the correct tire for a 7-inch rim. You can also go with the more common 225/50r15 if you don't mind carrying a little more diameter.

They don't look "bubbly" and you will want the extra width.

I run 205/50r15 on the stock 15x6 FC wheels. I am looking for some 15x7's so I can go to 225's.

-b

+1, either one of these is fine.

Currently, I have stock GTUs 16x7 wheels with 225/50/16 tires, and they look really bubbly, you can even see a rounded profile. The 205/55/16's that i have seem to fit properly though...

I'm using jimlab's formula for tire sizing which is width + 1 converted into mm. That brings about somewhere near 205, doesn't it?

There isn't an IT racer out there with 15 x7 running a 205 that I have ever heard of. 225/50 or 225/45. I have run these on 15 x 6.5 and 15 x7. If you want a narrower tire, go 205. If you want a greater contact patch, go 225. Maybe this will help...

http://www.hmsmotorsport.com/docs/To...Size_Chart.pdf

https://www.hoosiertire.com/rrtire.htm - go to R6/A6 section

Looking at the tire charts, I was always told to go a half-inch under the maximum, so for a max 7.5" width tire, I'd run a 7".

I think I'll be going with the Toyo Proxes R888's, so I'll have to see what size they come out in. The tire will mainly be for AutoX/HPDE. If the going recommendation is 225/45, then I'm hoping Toyo come out with that size.

That'll give you a more ideal wheel for a given tire, but that by no means says that you can't go narrower. You will be faster on the 225/45/15's than anything else. It's a track tire, it doesn't matter what it looks like, and the sidewalls are only minorly pulled in. If you'd worked it the other way around and started off with the 225/45/15 size then went looking for wheels then yes, a 15x8 would be better, but for a given wheel size it's usually faster to put a larger tire on (within reason, a 335 will slow an NA down)

I'd like to see a 335 in the back clear stock fenders!

That's actually what I thought when I bought my current RE-01R's in 225/50 as opposed to 205/55. I guess I'll probably do the same for my 7's.

So it's tire first, then wheel in the decision criteria, not the other way around? Hmm....Interesting.

Not necessarily, but the tire is more the limiting factor with how big you can go, then it'll generally be better to get a wider wheel if you can. It's not a simple matter of one then the other, it's a system, and free from rules it's best to pick them simultaniously to work together as best as possible.

Most of the time in racing the max wheel size is regulated, so it's all about putting as much rubber on it as possible.

A 225/45-15 fits just fine on a 15x7 (see pic). I'm running that combo on my FC for auto-x. I picked up a set of 15x7 Mustang wheels on CL for $45 (yep, for the whole set) and slapped on some closeout Kumho V700s. Not the absolute stickiest tires for auto-x, but way better than the Ecsta MXs I was running on before. And I LOVE the improved gearing.

When these wear out I'll likely go to the 225/50-15 V710.

which mustang wheels are those? I picked a set of 4 3-spokes for $50!

They are wheel type 'A' shown on this page, minus the center caps.

ic....I think I may have picked up the 3-spokes from the 01-04 Mustangs.....don't really know much about stangs in general, so....

Actually, it's from the 94 v6, 15x7, but I don't know how much offset it has.....anyone have any ideas?

I think they're all (the 15x7's anyway) 24mm.