Written by Andy Hollis
From the Oct. 2012 issue
Posted in Features
There is no denying the popularity of SCCA’s Street Touring category among the cone-dodging crowd. These street-friendly autocross classes continuously draw the largest fields, while others shrink.
Another option has been added to the card for 2012: Street Touring FWD—a new class for mildly modified, front-wheel-drive machines.
So which horse do you bet on? A head-to-head comparison test between the contenders would be ideal, but that requires some development time—plus the money to set up each car.
In the past, we have successfully used a shortcut: spreadsheets combined with a little intuition and background knowledge. Two years ago, we performed this exercise when the SCCA unveiled Street Touring Roadster, a similar class for fast, late-model convertibles. By analyzing the strengths and weaknesses of each of the eligible vehicles, we were able to successfully predict some winners.
A Little From Column B
Originally introduced in 1998 as an experiment, the Street Touring class was designed to attract the sport compact crowd from the street scene to the autocross course. The target vehicles were four-seat sedans and hatchbacks with small four-cylinder engines, and the allowed modifications included the typical bolt-on engine and suspension goodies.
The other key ingredient was the use of real street tires. The SCCA’s goal was to facilitate an arrive-and-drive type of experience—no second set of wheels mounted with dedicated race tires.
Whether that message reached the target market is debatable, but there is no doubt that the formula has become attractive among existing competitors. Recognizing this, the rule makers eventually added classes targeting other vehicle types popular within the SCCA ranks.
In 2002, Street Touring X was formed around the then-new Subaru Impreza WRX as well as rear-drive pony cars like the Mustang. The BMW 3 Series added some spice to the mix.
When the Subaru STi and Mitsubishi Evolution überboost buggies arrived in 2004, they were given their own playground in Street Touring Unlimited. High-performance sedans and coupes like the BMW M3 also joined the fray.
At the same time, older two-seaters like the early Mazda Miata and Honda CRX set up camp in STS2, later renamed STS. Finally, in 2010, STR became the home for the faster, more modern two-seaters already in the garages of many SCCA members—cars like the Honda S2000, Mazda MX-5 and Toyota MR2 Spyder.
As the original class within the category, the recently renamed Street Touring C has had the longest time for development. Veteran participants have carefully sifted through the eligible cars to find the one single model that best takes advantage of all the allowed modifications: the 1989 Honda Civic Si.
A large part of that advantage comes from the era in which that car was built, as this model predates airbags as well as the excessive comforts and conveniences that weigh down many of today’s cars. As a result, that 1989 Civic Si is light, weighing 700 pounds less than today’s version. When you’re asking a car to change directions, excess weight is the last thing you want, no matter how much power is under the hood.
Rather than ban an overdog, the SCCA has created STF as a place for newer front-drivers that just can’t out-handle the 1989 Civic Si. There isn’t anything more than 10 years old in the new class, and the focus is on the new B-segment microcars, like the Honda Fit, Ford Fiesta, Mazda2 and Fiat 500. Slightly larger front-drivers like the MINI Cooper, Acura RSX, Toyota Corolla and Scion tC are also invited. Strict tire and wheel limits—a 225mm tire on a 7.5-inch rim—have been mandated in an attempt to level the playing field between the smaller, lighter cars and the ones with more power.
Once again, there’s potential for big fields, as many enthusiasts already own these cars. They deliver great fuel economy and make excellent daily drivers. And with a few suspension and engine mods, they can deliver lots of fun between the cones. Which ones are potential winners? Let’s crunch some numbers to see.
Finding a Front Runner
As we did in our STR analysis, we worked from factory specs to generate theoretical performance indicators for this test. They help us understand a car’s strengths and weaknesses. Acceleration (thrust factor, in our formula) is important, but handling is the real key. We’ve found that the ratio of vehicle weight to tread width (grip factor) is a good predictor of that.
We also looked for any Achilles’ heel that could cripple a car—you know, something that could knock a seemingly top contender from competition. On the other hand, we also looked for things that could make a vehicle greater than the sum of its parts.
Our methods got a tweak this time around, however. In the past, we have made grip equal to three times the weight of acceleration. Since we have noticed more national-level courses with slower turns, we think a 2:1 factor might be better in some instances. We calculated our figures twice: once with each factor.
At the moment, the prevailing wisdom among top contenders—backed up by our own testing—is that the best tires for dry-weather autocrossing in the Street Touring category are either the Toyo Proxes R1R or the Hankook Ventus R-S3.
However, these two tires aren’t available in the optimal sizes for each analyzed vehicle, so we had to make some compromises and assumptions. For each car, we selected the best candidate—the tire that provides the best gearing and most stick. That meant the 195/50R15 Toyo for the lighter cars and the 225/45R15 Hankook for the heavier ones. Cars with shorter gearing needed to upsize to the 215/45R17 or 225/50R16 to avoid constant shifting. Now, on to the contestants.
Many of the pundits on various autocross forums have declared STF to be “yet another MINI class.” The popular compact will be a top contender for a variety of reasons.
Yes, it does well on acceleration and is reasonably light compared to the allowed tires. This accounts for relatively high ratings in both performance predictors. Gearing is just about perfect with the 23-inch-tall, 225mm Hankooks, and the car is heavy enough to warm the fronts to their sweet spot very quickly on course.
Aftermarket support is huge for the car, and the optimal autocross recipe for both generations has already been written by competitors who found success with the boosted Cooper S in the STX class. There are a lot of disgruntled H Stock competitors who are fed up with buying expensive R-comp tires—a stock, camber-challenged MINI likes to eat the fronts at an alarming rate.
Final Thought: The pundits may be right, as the MINI should be near the top of the STF heap.
Acura RSX Type-S
The power-to-weight folks seem to be hanging their hats on the Acura RSX Type-S thanks to its high-revving iVTEC engine and matching six-speed transaxle. Again, the aftermarket support is strong here, especially when it comes to making power. Simple bolt-ons and tuning can easily add 25 lb.-ft. of torque across the board.
There is a downside, though: Despite lots of available options, suspension tuning has been a challenge for these cars. They don’t respond well to significant lowering, and the rear suspension seems to have a mind of its own. Also, putting all this power down to the ground on corner exit may prove difficult without a limited-slip differential.
Final Thought: If the course has many slow turns, the RSX could easily become the car to have that day. It ranks right at the top on our 2:1 grip-to-thrust predictor, and midpack when using a 3:1 factor.
Through its partnership with Mazda, Ford has taken the latest Demio chassis and built the Fiesta on it. With a larger powerplant than the Mazda2 but more heavily loaded with features, the car’s numbers look very similar to the MINI’s. Curb weight and power are right in line.
The key difference is the gearing. It’s short enough that you’ll need a 25-inch-tall tire to avoid constantly shifting to third.
Final Thought: This one appears to be right in the mix.
With the Civic on a midlife weight-gain trend, Honda has returned to its roots with the Fit. Much like the early Civics, this car is light and lithe.
There have been two generations so far, and each has its merits. The first gen is lighter, makes a little less power, but is geared just right to run the 23-inch-tall tires.
The newer model adds weight and power, but short gearing dictates a taller tire. The resultant numbers are better than the MINI’s on both types of courses.
Final Thought: This car tops both performance predictors, so if one of these is in your garage, STF is calling your name.
Mazda has a few entrants into this scene, with their first-generation Mazda3 being a contender. Its 2.3-liter engine delivers the most torque of any of our target cars. The Mazda3 also doesn’t weigh any more than the RSX, but it does have unfortunate gearing that reduces the impact of that forward motivation.
Still, the Mazda3 ends up within striking range of the best on any course. Furthermore, the chassis itself is just plain sweet and delivers excellent driving dynamics. Plus, the performance aftermarket does offer some support here since the car has been around a few years.
Final Thought: This one could be more than the sum of its parts.
Another Internet maxim says the lightest car will always win the Street Touring battle. If that becomes the law in STF, then the Mazda2 will be a major factor.
Mazda has had an offering in the B-segment globally for over a decade with a model originally known as the Demio. In 2011, it was introduced in North America as the Mazda2—the new moniker is in keeping with the numerical naming conventions used here.
Integrating some of the manufacturing processes and materials that fall under Mazda’s SkyActiv banner, the Mazda2 is the lightest car in the class with a published curb weight just over 2300 pounds. Given its long run elsewhere, the chassis is well developed and the drivetrain is sorted—but aftermarket performance parts support is currently scarce in the U.S.
However, we expect the aftermarket to catch up, as Mazda is very much behind B-Spec, a road racing program for these B-class compacts. Mazdaspeed Motorsports Development has an off-the-shelf suspension kit based on Bilstein components, and various race shops will likely have turnkey exhaust and intake systems to sell.
The big question mark with this car is the gearing. The final drive is fairly long, and second gear doesn’t compensate much for it. Still, if enough weight can be pulled off the car during development, it might stand a chance.
Final Thought: Based on the published specs, it is a solid mid-pack performer.
Toyota does a great job in this segment with its Yaris model, and the numbers are fairly similar to the Mazda2. It’s light and has good power, but its long gearing means handling is its main advantage.
This is another car that should benefit greatly from B-Spec road racing, as performance parts are already being produced for it. Locally, we’ve even seen a club of five well-prepped cars show up regularly for autocrosses. Final Thought: If the Mazda2 is a contender, then is the Yaris right there with it?
One new car that is gaining a foothold in this segment is the Fiat 500. More of an A-segment microcar than a B-segment compact, the Fiat was still recently classed in STF.
While the engine has only a tiny 1.4 liters of displacement, it pumps out the same power numbers as the larger powerplants found in the Mazda2 and Yaris. And since the Fiat is just a bit heavier than those cars, it generates performance predictors in the same range.
However, this car has a secret weapon: It is a full 2 inches narrower than anything else in the class, and that translates directly into slalom performance. The rule of thumb says that every 6 inches of extra space a driver leaves between the car and a cone, 0.07 second is added to the time. While that doesn’t sound like much, it means that the Fiat can go through a five-cone slalom 0.1 second faster than the other cars. Now add up all the other left-right twitches on the typical course, and you get the picture.
Final Thought: The clever Italian gets to the finish line first by simply running a shorter course.
The Toyota Corolla hasn’t been a factor in autocross for a few decades, but maybe that will change. The 2003-’08 Corolla isn’t the fastest, lightest or smallest of the bunch, but it’s near the top in all the performance indicators—and that makes it a strong contender on on all types of courses.
Final Thought: If you want one car that can do it all, this is it.
Take Your Pick
So who wins? As much as we’d like to declare one overall top dog, there just isn’t a car that is substantially better than all the others. As in our STR analysis, there are a number of dogs here that can hunt, and it will come down to other factors, like depth of development and driving talent, that will likely make the most difference—at least in the first year for the class.
In addition, when dealing with grocery-getters—as opposed to the sports cars of STR—the likelihood of some hidden design oddity hampering a car’s performance is much higher. The big news is that STF has lots of possible front runners, which raises the odds that your trips to the store could get a lot more enjoyable.
You'll need to log in to post.
2 days ago in News
Find out in the next issue of Grassroots Motorsports.
5 days ago in News
Now is a great time to renew or start subscribing to our magazine.