My son is prepping our project 85 RX7 for Street Touring autocross. The smallest diameter tire for which we can get a good street touring tire. We were thinking of going with a 15x7 Diamond wheel (I like mine on my auctocross Neon), but are looking for advice regarding back spacing. I am concerned about brake caliper clearance.

Thx

 

4-1/2" backspacing is fine. Use the website listed below to check for clearance. Plug in all the values for the stock 13X5.5 wheel and go from there.

http://www.wheelsmaster.com/rt_specs.jsp

 

If you stay with 13" wheels, it is much easier to keep the center of gravity low. I've been running on 13x8 Revolution wheels for the last year, which replaced 13x8 Diamond Racing wheels (which do work great, but don't look as nice as the Revos).

Anyway, like I said it makes it a lot easier to keep things nice and low. Check out my videos if you get a chance, and let me know if you have any questions.


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Yeah, but he is in street touring. This means no R tires. No one makes a street touring tire in a 13 inch diameter.

 

Sumitomo HTR 200. I've been tearing Miatas new, um, holes, for some time now with these. As long as they are on the right wheels, they totally kick ****. Even against a supercharged Miata on race rubber, with three drivers (two of which are very good), my Sumis came through for me. What more can you ask for in a $45.00 tire?

I run 215/50/13 on the 13x8 wheels, and they are a very happy combination.


http://www.youtube.com/watch?v=rWpEYAKo0fU

 

That is interesting you mention the HTR 200s. Last year, Grassroots Motorsports Magazine did a test on street tires which "can" be used for autocrossing and the HTR 200s did well. I was actually thinking about the HTR 200s at onepoint. If that is the case, I would run the widest I could fit on the stock 13 inch wheels.

 

I have run the 215s on the stock (+) style rims, which are 5.5 inches wide. I did that for about three years. The only issue is that you get a bit more sidewall bulge, which results in some flexing of the tire on hard corners. I think the 205s that I ran before were actually a bit happier on that wheel.

But when I changed to the 8" wide rims, using the same 215 tires, the difference was incredible. The tires just fit a lot better on those rims.

Last I checked, you could get 13x8 wheels from Diamond Racing for about $300.00 plus shipping. Or, sometimes you can find them used. I actually have a set that I am considering selling, since I have no use for them now. Otherwise, 205s on the stock rims should fit your needs well enough to get started.

 

I would go with a 15x7 wheel there are may more options for you with a 15" tire.
you can fit a 225-50-15 tire under an rx7 fender if you strech the fender , but 205-50-15 is a very common size and will fit. almost every tire company makes a great st tire in that size. as matter of fact grassroots motorsports just did a test of the current crop of st tires.
good hunting

 

btw to answer your original question brake caliper clearance isn't usually the issue, it usually front strut clearance or fender lip clearance.

 

Best Diamond can do is 4 inch backspace

 

That's what my Diamonds are, and they fit great...