Apparently Size Matters

Update by John Rogers to the Mazda MX-5 Miata project car
Apr 2, 2010

Testing tires at The Tire Rack.

It’s a question racers often ask: How much faster are proper competition tires than regular street tires? One second? Two? Three or more?

Thinking back to our first competitive outing with the bone-stock car at the Dixie Tour, we were easily 4-plus seconds off the pace of the prepped cars on proper tires and wheels. We had a lot of ground to make up.

Recently we ran some baseline laps with the OE 205/45R17 Bridgestone Potenza RE050A wheel-and-tire package. Then, after doing nothing else to the car but bolting on the 255/40R17 Dunlop Direzza Sport Z1 Star Spec tires wrapped around 17x9 TRMotorsports C3 wheels, we were well over 2 seconds faster on a 55-second course. As you would expect, steady-state lateral g-loads were higher, too.

Next up, we’ll install the coil-overs to see what sort of difference upgrading the suspension can make.

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View comments on the GRM forums
Nick_Comstock PowerDork
11/17/14 9:26 a.m.

Are you going to test the factory tire setup again after the suspension mods?

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