Gaining Grip

After more than a year of enjoying big turbocharged power with our Miata on an otherwise stock suspension and commuter-grade tires, we’ve finally upgraded the running gear of our car. The factory spec R-package suspension had held up well and was free of squeeks and rattles. On the other hand, the factory springs and shocks weren’t prepared to handle the sort of power we were making with our Flyin’ Miata turbo setup. The setup could be kept under control for street driving, but it was really out of sorts on the autocross course. Fear not, however, as we used this opportunity to evaluate a few different aftermarket solutions in our quest for a dual-duty street car.

Our first step was pretty obvious; rolling around on $60 budget tires wasn’t going to cut it among the fast cars in the SCCA’s Super Street Modified class. The fastest choice for tires would have probably been Hoosier’s 275/35R15 A6, but that tire is more of a purebred than the the hybrid street and competition solution we wanted. Our dual-purpose tire dilemma was solved with a set of Nitto NT-01 tires in the large but reasonable size of 225/45/15. We wanted to leave the Hoosier option open, so we decided to try a set of 949 Racing’s 6UL wheels in a massive 15x9-inch size. Incredibly, even in a 9-inch width these wheels weigh less than 13 pounds. They’re designed specifically with Miatas in mind, so these wheels are about as big as you’ll be able to fit under an early Miata without significant modification. They can accommodate the Nittos or the Hoosiers without any fuss, so if we decide to take the car to a national event we can go with even bigger, stickier tires.

We liked the fact that the factory Bilstein shocks had held up to more than 100,000 miles of wear without failing, so we decided to stick with their products on our project. We installed two different sets of Bilstein-sourced coil-over assemblies on the car. The first was their premium PSS9 coil-over set. The second was the Fat Cat Motorsports Variant coil-overs; the FCM units use custom valved Bilstein shocks mated with stiffer springs and adjustable spring collars. We wanted to find the best handling solution that wouldn’t jar our bones during trips around town, and only testing would help us find it.

We also upgraded the anti-roll bar to a Racing Beat tubular unit that we sourced from Good-Win Racing. We anticipated a marked increase in grip, so we also included Racing Beat’s reinforcement blocks to keep the anti-roll bar mounts from tearing under load. (We’ve seen this happen before on Miatas that are capable of huge grip, and it doesn’t look pretty.)

Look for the complete review and test results in an upcoming issue of Grassroots Motorsports.

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