The NB Miata I bought was being used as a CSP car. The seller included a sweet set of 13" Rotas. My plan is to track the car more than auto-x it, and I'm thinking about 15" wheels for that. Researching options led me to wonder why folks use such small wheels for auto-x. Is it all for gearing purposes? Some other good reason?
Usually tire availability.
Plus, it's easier to fit a 13x10 wheel under a Miata fender than it is a 15x10.
Interesting. The 13" wheels I got with the car don't seem terribly wide. I know they have 215/50/13 tires on them. And 13" tires are easier to find that 15" tires??
dyintorace wrote: Interesting. The 13" wheels I got with the car don't seem terribly wide. I know they have 215/50/13 tires on them. And 13" tires are easier to find that 15" tires??
13 inch RACE tires. My RX7 is the same. For race rubber I would run 13's for Street rubber, including the newest Street AX tires, it would be a 15. Cars are just a device for making the fastest tires you can fit go fast.
The 255/40R13 Hoosiers were pretty popular on Miatas in CSP for a while before people really figured out how to fit the 275/35R15s.
If only they made street rubber in those proportions. 275/35R15 is just about perfect for my Quantum, or anything else that you want the wheel/tire proportions of a Group 4/B Audi.
http://www.bufkinengineering.com/Michelin%20Tires%20and%20Fender%20Flares.htm (those Coker tires are something like $500. Each.)
I remember when BFG and (McCreary?) made 235/50R13 street tires...
On low powered cars there is also a weight advantage to using smaller wheels. Lower rotational mass and unsprung weight. And if you are going full race tires, you can choose tires without steel belts in them, which makes the weight savings very significant (could be as much as 25# per corner).
There is a wider variety of tires available in 15" for street uses, including DOT legal autocross. But, for venues that permit real race tires (non DOT legal), there are more choices in 13".
Depends on what you are doing.
For El Rabbitto I run the 13's for gear ratio as well as weight. Would be tough to stuff 245's of any other size under it.
I'd think it drops the car an inch closer to the pavement with an equivent sidewall for absorbing bumps and pavement irregularities too. But I'm no autocrosser so it's sheer speculation.....
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