That’s the question we often hear from the staff at Harris Hill Raceway–which we usually visit once or twice a week.
Sometimes we’re there for a full-on, multi-tire, back-to-back, bracketed comparison. More often than not, however, we’re simply visiting to run a single tire through its paces to experience it as any typical enthusiast would.
Choose Wisely
When SCCA moved its emphasis away from R-comps to street tires several years back, the mantra was simple: “Make it easy, make it fun.” And in those days, saving money on consumables certainly added to the enjoyment. Street tires were less expensive and more durable, and the choices among them were few.
Fast-forward to today, and there are endless tires to choose from, each with widely ranging characteristics. Fortunately, we’ve done most of the heavy lifting for you with our Ultimate Track Tire Guide–find it online, while the summary chart can be found at the end of this article. All of today’s top tires have been scientifically tested and rated, so you can make an informed choice. And those ratings are tweaked as we learn more in our weekly track outings.
For top-tier autocross use, you’re going to want a fast tire whose compound turns on quickly in your application. Typically, that means a Yokohama Advan A052 or Bridgestone Potenza RE-71RS, rated A for both Pace and Warmup. With its B rating for Warmup, the Vitour Tempesta P1 may be an option for a heavier car or warmer weather; it can also be an option if you’re willing to throw away the first run.
If time trials are your thing, immediate warmup is less important, as heat can be built through additional laps. The Nankang CR-S V2 joins the P1, A052 and RE-71RS as prime A-pace candidates, with the first two giving more quick laps based on their Heat Tolerance ratings. By contrast, the Yokohama is notorious for being a “one and done” TT tire in many applications.
In short, it’s all about heat management: getting a tire into its optimal temperature window for your use case and keeping it there as long as necessary.
Getting Fitted
Sometimes the model of tire you want doesn’t come in an optimal size for your vehicle. You either have to choose another less suitable tire or compromise on size. One of the benefits of the Vitour P1 is a wide range of fitments, with a promise of 65 sizes by the end of this year.
SCCA Solo’s Street category brings with it restrictions on wheel width and camber, so the stiff-sidewalled RE-71RS tends to be a favorite there. By contrast, Street Touring’s wide wheel fitments and plentiful camber make it a perfect playground for the A052. The unique, superwide P1 sizes promise to be favorites in CAM and XS, where getting big power to the ground is key.
Preparing for Battle
Once you’ve selected a tire, it’s important to properly prepare it for the abuse we call motorsports. At the very least, you’ll need to scrub off the shiny mold release lubricant before it will deliver any grip at all, especially in the wet.
Even better, a mild initial heat cycle will condition the rubber by realigning the molecules with stronger bonds. This process makes the tire more durable, consistent and oftentimes faster.
You can either pay your retailer to perform this heat cycling by machine or do it yourself. All of our test tires get six laps at ever-increasing intensity up to about 90% pace, whereupon they are allowed to cool for at least 24 hours off the car. Alternatively, 40 minutes of highway driving on a warm day can also do the trick.
Tread Depth: Less Is More
Purebred racing slicks, and their closely related R-comp cousins, deliver the highest levels of grip for motorsports. A key feature is their thin rubber tread caps–typical 4/32 inch–with no tread blocks to squirm around and generate excess heat. This allows for softer compounds to be well supported, delivering better grip and consistency over a session.
To optimize 200tw tires, this trait can be mimicked by wearing treaded street tires to lower depths. Some tire models benefit more than others, but we’ve yet to find a street tire where it had no positive effect. Here’s some examples.
Last fall, we pitted fresh sets of the top 200tw tires against each other in a same-day test. We then brought each to the track, one by one over the next couple of months. Three months later, they had all been worn to 5/32 inch, albeit with some significant differences in the number of laps it took to get there. The Nankang CR-S V2 was the durability king, with the A052 and RE-71RS bringing up the rear halfway back.
We then took the whole lot to Harris Hill Raceway again for a head-to-head, same-day showdown to see how their relative performance had changed. All turned quicker times that day, but the A052 and RE-71RS had caught up to the P1. The CR-S V2 also improved by a full second, but it was still a few tenths off.
Another data point comes from our recent test of the Hoosier Track-Attack Pro, a 200tw tire that comes already molded to 5/32 inch. In that test, we compared the Hoosier to two sets of the RE-71RS–one fresh at 7/32 and the other worn to 5/32. The two versions of the Bridgestone were separated in pace by the same 1-second margin as our earlier P1 tests.
Does this trend continue as the tire wears to even thinner depths? Our experience tells us yes, but the improvements come slower. We’ve run 1:24.0 laps on the RE-71RS and CR-S V2, both at 2/32 inch.
Need more proof? Here’s a long-term study of the TrackAttack Pro. Note that ultimate pace on any given day is dependent on track and weather conditions, but the trend here is pretty clear.
With continued use, handling eventually changes for the worse. All of those additional heat cycles slowly rob the rubber of grip to a point that outweighs any benefit from reduced tread squirm and lighter weight. The tire takes more and more running to come up to temp and gets very edgy at the limit. For some tires, you may never get to the cords before this happens–the Falken RT660 is one.
One way around this is to shave the tires to the optimal depth before running. While not as cost-effective for long-term usage, it can be key to winning an important event–in our case, the SCCA Time Trials Nationals. For the past three years, we’ve fitted our Max 5 class-winning Honda CRX with Yokohama A052s shaved to 4/32 and heat cycled by Tire Rack. Since the rules limit competitors to one set of tires, ours were in their sweet spot for the entire four-day event.
If you do choose to pre-shave your tires, you can expect to gain a bit more performance after they’re run for one or two sessions. This final operation establishes the wear pattern for each corner of the car, according to pressure and camber settings.
One of the key benefits of lower tread depths can also be a downside, however. By generating less heat, the tire is more consistent–but also takes longer to turn on. So, if you’re autocrossing on a cool day with a relatively light car and a single driver, you may be at a disadvantage. The Tread Depth Sensitivity column in the Guide is your key here. Think of it as a modifier on the Warmup column.
