New Wheels and Rubber for Our MX-5

Update by Per Schroeder to the Mazda MX-5 Miata project car
Mar 30, 2010

Rear tire install.
Rear tire clearance check.

The factory tires and wheels on our Mazda MX-5 looked fine for the average driver, but this project isn’t about being average. It’s about being competitive in the STR class, and that means upgrades.

We test fitted the tire and wheel upgrade using the widest tires allowed by the rules: 255/40R17 Dunlop Direzza Sport Z1 Star Spec tires mounted on 17x9.0 ET48 TRMotorsports C3 wheels. The mild-mannered MX-5 now looks more like a steam roller with this package on board. We can’t wait to see how much this bolt-on upgrade helps lap times.

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View comments on the GRM forums
EvoRoadster New Reader
4/9/10 9:25 p.m.

Nice rims. I just had Tire Rack send me some 15x9 TRMoto C3s with Hoosier 225-45/15 A6s mounted for the new autox season.

chknhwk HalfDork
5/10/10 7:52 a.m.

That's interesting, you're using chalk to see where/if the tire rubs? I like that! Much better than taking the car to the track and seeing all the slices in my sidewalls from the fender. LOL

superblackser New Reader
7/26/10 11:53 a.m.

No kidding? Those a 255's, not 225's? Wow. That's a huge amount of rubber for that car. Tire Rack lists those as 28 lbs per tire (!). The closest RE050 they list is a 215/45/17 but I am guessing that is close, 22 lbs listed. SIX pounds per corner of rotating weight increase due to tires alone? I balk at going up to a 215 or 225/15 tire (even with street vs. comp tires) from my 205/50/15 set because of the 2-3 lbs per corner added weight, with my 7"x15" Motegi Traklites on my '91 SE-R I am only looking at most 29 lbs per corner with wheel AND tire (Kumho XS, Nitto NT01). That's only one lb more than just that tire if you believe published weights (my rims are correct, they are 4.4 kg spot on). How do you know that a 225, 235 might not have been just as fast or faster? After a point enough grip in a lower-powered car is going to be offset by acc/decel that added weight.

Tom Heath
Tom Heath UberDork
7/28/10 8:53 a.m.

@ Superblackser:

The guys at Tire Rack have the opportunity to test nearly any combination of tires and wheels you can think of. They're using the 255s because they are faster than other options, at least in an autocross environment.

Check some of the other updates; the results speak for themselves!

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