Solo Street Class Prep: RX-8

A few general rules apply to preparing any car for the SCCA Street class in Solo; there are also some specifics to help you get the most out of your Mazda. Let’s start with the RX-8.

SCCA Solo rules have undergone a major revamp; what was once the Stock class is now called Street, and there’s one rather big difference – no longer are R-compound tires allowed. Rather, the rules dictate a Uniform Tire Quality Grade Standards (UTQG) 200 treadwear rating, a number determined by the manufacturer or a testing firm the manufacturer employs.

Fortunately, tire manufacturers are stepping up to the challenge and producing tires that meet the criteria. That means a lot of choices. After choosing a car that’s competitive in its class, whether it be RX-8, MX-5 or Mazda3, among the recent Mazda options, tires are the next most critical choice, says Chris Harvey, a nationally competitive autocrosser in C Street with an MX-5 and also the brand manager for Brakes & Supension at The Tire Rack.

“At The Tire Rack, we categorize these tires as extreme performance,” he says. “There will be lots of test information on our Web site as well as other sources out there that can help guide you to the preferred tires for the class. A 200 treadwear rating is the limitation the rules committee has put in place, and the tire manufacturers have caught on to that and have delivered multiple options now that are available for just about any given car that might be competitive.” Remember that a tire that meets the 200 rating may not be permitted; check the rulebook.

From that point on, the gains get smaller. A proper alignment is the next step in getting the car to work on the autocross course.

“The maximum negative camber you can get within the OE design parameters is allowed by the Street class rules, so maximizing the front camber is the typical first step that everyone goes to. For the toe settings, a lot of that comes down to the particular platform you’re dealing with, or driver preference, how the driver likes the car balance. You play with the toe settings to reduce understeer or try to achieve some oversteer. That really comes with time and experience with what you prefer and what ends up ultimately being the quickest settings for you,” explains Harvey, who owns and set up the MX-5 that finished second (Chris Fenter) and fourth (Harvey) in C Street at the 2014 The Tire Rack Solo National Championships.

From there, the rules allow modifications in three main areas: shock absorbers (same type and mounting points, up to two external adjustments); the substitution, addition or removal of one anti-sway bar (front or rear); and the exhaust past the catalytic converter. Each of these may help, and cumulatively may add up to a few tenths on any given course. However, Harvey says there is one more thing to fine tune before one starts swapping parts.

“The beauty of the street class is the primary thing is fine tuning the driver, number one. When you get to the pointy end of competition, where you’re really battling for those last few spots, the car preparation becomes much more important. But for someone who is just getting started, selecting the correct car and correct tires is a great starting point, but ultimately you can take the best driver and put them in an under-prepped car and they’re going to do extremely well. Honing the driver and focusing on improving…there’s much more time to be gained than subtle changes to the alignment and shock settings and that kind of thing,” he says.

Jason Isley is familiar with the pointy end of competition. The SportsCar magazine associate editor won four-straight Stock class titles in an RX-8 from 2004-’08. His wife Jennifer is also owner of a couple of Stock class titles on the Ladies’ side. While those titles were taken in the days of the R-compound tire, his testing indicated that setup wouldn’t be much different.

“We actually did test it when we were doing a [SportsCar magazine] tire test,” he explains. “We ran it on street tires as well, and we went through the process of what we would change, because we weren’t happy with the gap that we were getting [between race compound and street compound times]. We found we needed a little more front sway bar with the street tires.”

Isley’s recipe for Stock class success was Koni sport shocks, all at full stiffness; the MAZDASPEED front anti-sway bar; and a single-side exhaust to minimize weight. When testing the street tire and discovering the need for a bit more roll stiffness up front, Isley says the Hotchkis MX-5 bar did the trick. Then it’s just maintenance – change the plugs once a season and the coil every other year to keep things in top shape.

“Other than that, lots of camber, a lot of front toe-out. We ran about a quarter-inch toe-out in front because it’s a long car and doesn’t like low-speed turns. A lot of front toe really helped it around.” Isley adds that driving the RX-8 requires a bit of patience, saying that in tight turns you have to get the car stopped, then turned to avoid too much push.

Coming soon, some MX-5-specific Solo setup tips.