Written by Per Schroeder
From the Aug. 2009 issue
Posted in Tires & Wheels
Tire wars are a given in the motorsports world, but imagine where we’d be if the industry lacked its healthy fondness for performance advancements and old-fashioned capitalism.
Let’s say tire technology froze in 1955. That means we’d still be driving on bias-ply tires that generate half the grip of a modern radial—high-speed stability, durability and safety would be dubious at best. Or how about if progress had stopped in 1988? The Yokohama A008R would be the hot autocross tire. And if the tire companies had halted all development after last issue’s tire test, the Kumho ECSTA XS would remain the eternal street rubber champion.
The Kumho ECSTA XS was king of the hill in our last tire test, as it captured both the fastest single time and lowest average time. Meanwhile, the XS narrowly beat out the Bridgestone Potenza RE-11 and the Toyo Proxes R1R in a close battle.
Fast-forward just one month, and the Yokohama Advan Neova AD08 has rolled onto the scene as a new contender. The AD08 was not available in time to make our earlier test, but there was some buzz that it could have been a winner.
We didn’t require much arm twisting to hold a follow-up comparison. Could the supposedly stellar Yokohama upset the Kumho? And to make this more than just a simple A-B comparo, we decided to retest the Bridgestone RE-11. The Bridgestone was only a few clicks behind the Kumho; was that a fluke, or is the Kumho really the superior tire?
We also decided to add one more variable to the mix, the 225/45R15 Toyo Proxes R1R. While the rest of the tires that we tested last time were 205/50R15s, the wider size could be enough to give the advantage to Toyo.
Our test procedure was identical to the last one, as we again had multi-time national champion Andy Hollis wheel his Street Touring 1989 Honda Civic Si around the test track at Driveway Austin. We even used the same course, including the seven-cone slalom as well as a good mixture of low- and high-speed sweepers. Each tire was shaved to 3/32 inch and set to its optimal tire pressure during our scrubbing-in process. The tires were mounted on identical sets of wheels, and each set took four laps around our course.
Since the Kumho was the winner in our previous evaluation, we decided to use it as this test’s benchmark. We first ran the Kumho, followed by the Bridgestone, Toyo and Yokohama. We then ran the Kumho an additional four laps at the end of the day to ensure that the conditions remained the same during our test. Once again, AXWare System’s Vitek Boruvka handled the timing chores with his super-reliable timing rig.
Kumho ECSTA XS
Mean Time: 35.032 sec.
Quick Time: 34.842 sec.
The Kumho ECSTA XS is an excellent tire, and our love from the earlier test was rekindled immediately. Corner entry was on the money with great turn-in response, and the tire really put down the power nicely when coming off the corners. Slaloms were also super-fast. In short, the tire repeated its stellar performance from last issue’s test.
The XS established a strong benchmark average of 35 seconds flat and a quick time of 34.8. The lap times deviated little from one another thanks to the Kumho’s unparalleled driving precision.
Bridgestone Potenza RE-11
Mean Time: 35.398 sec.
Quick Time: 35.262 sec.
The Bridgestone RE-11 felt similar to the Kumho as far as crisp slalom performance, but its turn-in was not as sharp. The Bridgestone also exhibited a delay in power delivery when compared to the Kumho.
The Bridgestone RE-11 seemed to like more air than the other tires. It generated its fastest times at around 43psi, while the other tires preferred settings in the mid-30s. The Bridgestone’s times were about three-tenths behind the Kumho on average, with a fast time of 35.262. Once again, close, but no cigar.
Toyo Proxes R1R
Mean Time: 35.356 sec.
Quick Time: 35.264 sec.
To put it simply, the 225/45R15 Toyo Proxes R1R is big and fat. Tires with wider footprints typically perform well in long, sweeping turns but struggle to keep up in transitional slaloms. The bigger Toyo isn’t a typical tire, however.
Thanks to awesome grip and response, it set fast segment times in our slalom. Unfortunately, sustained cornering was the Toyo’s downfall: The tire tended to overheat and fall off near the ends of long corners, limiting how much power we could put down when coming out of a curve.
During this test session, the Toyo nearly matched the Bridgestone’s times. The tire’s additional width seemed to make little, if any, difference in its final ranking.
Yokohama Advan AD08
Mean Time: 34.972 sec.
Quick Time: 34.827 sec.
The Yokohama Advan AD08 felt very similar to the Kumho ECSTA XS in terms of grip and response to steering input. The newcomer was very confidence-inspiring upon corner entry and easy to modulate mid-corner. Power also went down nicely coming off the corner.
Like the Kumho, this tire communicates with the driver and exhibits good audible feedback as it approaches the limit. The AXWare Systems timer backed up this fact, as the Yokohama achieved the fastest mean and quick times at this point in the test.
The Yokohama did appear to get too hot near the end, and as a result performance fell off a bit during our third and fourth runs. We particularly noticed this issue in the final sweeper, where the tire would become loaded for an especially long time.
Compared to the Kumho, the Yokohama was simply not as consistent in the slalom, although the Yokohama’s first run garnered the single fastest slalom split of the day. Perhaps with some more seat time, this tire could be right there with the XS (see below).
Kumho ECSTA XS (Retest)
Mean Time: 34.728 sec.
Quick Time: 34.541 sec.
After running the new Yokohama, we gave the Kumho another go to ensure that our test conditions had remained consistent.
The Kumho posted slightly better times during its second session, circling the track a few tenths faster than before and sneaking ahead of the already quick Yokohama. The times from both Kumho sessions were close enough to indicate that conditions and course familiarity didn’t have a significant impact on our results.
Gaga for Grip
These last six months have seen some unprecedented action in the max performance street tire scene. New releases have blasted away the old standbys, giving the hardcore enthusiasts a plethora of choices.
The latest crop is leaps and bounds better than those from seasons past, and each model has its strong points. The 225/45R15 Toyo R1R is an amazing tire for transitional courses, while the Kumho ECSTA XS and Yokohama Advan AD08 will dominate on sweepers and mini-road courses. The Bridgestone RE-11 is the Jack-of-all-trades choice, as it can tackle any situation with ease. One possible player is missing from our test, as the Nitto NT05 still isn’t available in a 15-inch size. Sizes start at 17 inches, and based on our experience this Nitto could be a contender for the larger Street Touring-class cars.
One thing hasn’t changed, however: Personal preference and car setup are still important factors when choosing autocross rubber.