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Top Tires

We were wrong. So very wrong. You see, this time last year it appeared that every major performance tire manufacturer had recently revamped their top-shelf, ultra-high-performance tire model. So when we compared them for our annual street tire shootout, we figured we’d have a couple years off before doing it again—especially when we did a follow-up test to include a couple of late additions. Bzzzt! Incorrect! Try again.

Since that time, two major new entries in the UHP category have been introduced: the Hankook Ventus R-S3 and the Falken Azenis RT-615K. Plus, Dunlop finally decided to import their highly respected Direzza Sport Z1 Star Spec in additional smaller sizes that better suit our Honda Civic test vehicle. Are any of these newcomers good enough to unseat last year’s champ, the Kumho ECSTA XS? Time to find out.

All test tires arrived shaved to 3/32 inch and were expertly mounted on identical wheels by our good friends at SoulSpeed Performance of Austin, Texas. We ran our usual wheel setup: 15x7.5-inch SSR Type-Cs in the front and 15x7-inch Enkei RPF1s in the rear.

Each tire was delivered in a 205/50R15 size, with the exception of the Hankook—the only currently available 15-inch size is the slightly wider 225/45R15. Tires were scrubbed and optimal pressure ranges were established on a skidpad at Mineral Wells, Texas, two days before the site hosted an SCCA National Tour. Typically, each tire has a range of pressures in which it can still be tuned for feel without affecting performance.

The SCCA Solo Nationals are now held on concrete, prompting a pressing question: What tire is fastest on that type of surface? To find answers, we chose a concrete site for our autocross test.

We again arranged to use Pennington Field’s super-clean lot. It’s the same place we ran last fall’s comparison between R-comps and street tires. This year’s course was a two-lap affair, featuring a long slalom, a series of offsets, and both on- and off-camber sweepers. This setup provided a good comparison between braking, transitional handling, steady-state grip and power delivery. We also ran a 150-foot skidpad, and calculated the lateral g loads for each tire.

As reigning champ, the Kumho served as our baseline. We ran it first and last, with the second heat serving to bracket the results and verify that no course or driver improvements were at work.

Testing requires the utmost in consistency, but also a constant push for higher limits. To that end, we mounted and ran each tire for four two-lap passes. We took a short rest between runs, and any drop-off in performance and/or feel was met with some aid in the form of the water sprayer.

Results reflect the single best lap for each tire as well as the average of the best three. In addition to times, driver impressions were also recorded as the car came off the course.

But wait, there’s more: We also did some track laps with our four tires so we could see how the autocross performance translates to higher speeds and longer sessions. Harris Hill Road in central Texas, a medium-speed handling track, served as the perfect testbed.

On the road course, each tire was again exercised over a series of laps. However, this time they were run back-to-back with no intermediate cooling period. This represented the demands of a typical time trial or short HPDE session. A 70-percent warmup lap was followed by three 100-percent timed laps. We then ran a cooldown. Results reflect the best single lap, followed by the average of the best two.

Last Year’s Standout: Kumho ECSTA XS

average autocross run: 43.370 sec.
fastest autocross run: 43.258 sec.
average track lap: 90.719 sec.
fastest track lap: 90.699 sec.
lateral acceleration: 0.956g
retail price: $92

After years of playing second fiddle with their MX model, Kumho’s new XS propelled them to the top of the heap during last year’s tire test. Since that time, the XS has developed a reputation as a solid track day performer and strong autocrosser. This year it came right out of the box kicking hard.

Prodigious lateral grip is the tire’s strength, and it showed well through our autocross sweeper sections. Slalom performance is solid, but it takes a bit of familiarity as there is a slight off-center delay in response to driver inputs. Longitudinal grip, however, is less than stellar and hard to modulate; we got wheelspin off the line and periodically locked the brakes on the downhill run into one of the sweepers.

The XS loves heat and really delivers once it warms up. Each lap of the autocross course was a tenth faster than the previous one—until the times stabilized on the third run, when we cranked off four laps within the same tenth.

On the road course, a single warmup lap was enough to bring the tire up to speed, and we zipped off quick laps right from the start. We did have a lockup problem on our final lap, as the tire had some trouble over a bumpy braking zone. That lap was a throwaway.

Downsizing a Favorite: Dunlop Direzza Sport Z1 Star Spec

average autocross run: 43.506 sec.
fastest autocross run: 43.295 sec.
average track lap: 91.433 sec.
fastest track lap: 91.337 sec.
lateral acceleration: 0.956g
retail price: $107

The Dunlop Direzza Sport Z1 Star Spec has done very well in national-level autocross competition, especially on heavier vehicles. Priced at the lower end of the UHP tire segment, the Dunlop is also a great performance value. It has also earned a reputation as a great daily driver tire as well as a favorite for the track.

Until recently, though, Dunlop kept all of its smaller sizes overseas for the Japanese company’s domestic market, seeing the U.S. only as a venue for the larger sizes.

Lucky for us, they finally saw the light and brought over some very interesting new sizes, including the 205/50R15 we needed for our Civics. Would that big-car success translate to the little guys?

Our hopes were high as we began and, sure enough, the Direzza Z1 was right there with the others on the skidpad. On the autocross course, the Dunlop delivered strong grip but was rather vague in feel, making it a challenge for us to find the limits and stay there. This situation was exacerbated by heat, as each run’s second lap was always slower than the first one.

To combat the greasiness, we sprayed down the Dunlops before the third runs. We were rewarded with a two-tenths drop in lap times. Unfortunately, the second lap of that run was again slower than before. On the race track, the tire was very consistent but also a tad slower than the best. The long and repeated cornering loads of the road course seemed to put the tire out of its highest grip/heat zone. Still, lap after lap, it delivered solid performance with no further drop-off.

Is Falken Back? Falken Azenis RT-615K

average autocross run: 43.535 sec.
fastest autocross run: 43.433 sec.
average track lap: 92.131 sec.
fastest track lap: 91.948 sec.
lateral acceleration: 0.967g
retail price: $147

Back in 2002, Falken pretty much invented this category of tires with their Azenis RT-215. Lauded for its crisp response, prodigious grip, long wear and low price, it dominated autocross street tire classes and track day use for years.

Falken’s follow-up, the Azenis RT-615, lacked some of that response, but grip was improved. Still, competition in the market segment intensified and others rose to the top. In fact, Falken was well off the pace in last year’s GRM test.

Fast-forward to 2010, and Falken is back. A compound-only upgrade has given Falken a new player—the RT-615K. (The K stands for kaizen, a Japanese term for “continuous improvement.”)

We admit we were giddy when we completed our skidpad work and found that the new Falken generated higher lateral acceleration than the others. We had to wait four long days for the autocross test, and the anticipation was almost too much.

As test day arrived and the Falkens took their turn, we were immediately comforted by an old familiar feeling. The same communicative turn-in response of the original RT-615 was still there, but with more grip—much more grip. It was like enjoying our favorite ice cream flavor, but now with chocolate syrup on top.

However, there was trouble lurking. The harder we pushed the tire, the greasier it got. The K-compound still had the Achilles heel found in the original tire: poor heat tolerance. Judicious use of the water sprayer brought back some of the performance, but not enough for an entire autocross run. Once the tire was overheated, it could not be revived entirely.

Things were less rosy out on the track, as each successive lap got slower and slower. That communicative feeling turned into mush in the face of multiple laps at 100 percent. In short, the Falken is fast and friendly, but it requires some extra effort in terms of heat management. The Azenis could thrive in colder climates, however.

Finally Fulfilling an Old Promise: Hankook Ventus R-S3

average autocross run: 43.076 sec.
fastest autocross run: 42.948 sec.
average track lap: 90.668 sec.
fastest track lap: 90.539 sec.
lateral acceleration: 0.956g
retail price: $115

Five years ago, Hankook released the R-S2 version of their Ventus race tire with much fanfare, including a strong marketing presence and contingency programs aimed at our market. The tire scored a number of wins at first but eventually fell behind the times.

The sizing, construction and compound were all good, but the tread design simply had too much void area. In short, there wasn’t enough rubber to meet the road.

The all-new Hankook Ventus R-S3 has improvements in all areas, but most notable is the new blocky tread design. Sporting enough channeling to be reasonably effective in the wet, the tread shaves nicely into a wide, square-shouldered surface not unlike that of the Dunlop.

Though sizing is still somewhat limited, the extremely popular 225/45R15 pioneered by the R-S2 is on the list of offerings. This is a size that nicely matches the Street Touring rules, as it’s the maximum permitted width and fits well on the allowed 7.5-inch-wide rim.

Though it missed our tests last year, the R-S3 has been available since late last spring and has seen some autocross success at national-level events. It has also made some inroads to the track day crowd. In particular, the 225/45R15 Hankook works nicely on Miatas sporting 15x9-inch wheels. It also fits well on Hondas running 9-inch front wheels and 8-inch rears. For our tests, though, it was mounted on narrower wheels, eliminating much of its size advantage over the other brands.

In testing, the R-S3 started off fast and just got faster. It offered huge grip, excellent communication and super-consistent performance. Like the Kumho XS, the new Hankook likes some heat. It experienced some wheelspin during our first launch, followed by a slightly slow initial lap. However, it came up to speed much faster than the Kumho and stayed right there throughout. Outside of the first pass, all times were within a tenth and a half of one another.

On the track, the heat profile was just about perfect; the tire was effective immediately and did not fall off for our entire three-lap stint. While not as crisp as the Kumho, the Hankook tied its session average and delivered the quickest single lap. Corner-exit power delivery was better, and so was braking performance. Acceleration, however, was a little off due to the higher weight of the Hankook versus the lithe Kumho.

Retesting Our Benchmark: Kumho ECSTA XS

average autocross run: 43.495 sec.
fastest autocross run: 43.399 sec.
average track lap: 90.708 sec.
fastest track lap: 90.504 sec.

Before calling it a day, we always retest our first tire. Did the track, car or driver get faster or slower as the day progressed? Of course, this retest is always accompanied by a bit of nervousness. If these numbers don’t match the first test, then we may have some investigating to do. This year, fortunately, the stars aligned and everything repeated almost perfectly.

In the autocross test, our second stint on the Kumho was within a tenth on both lap times and averages. On the track, we repeated our session average but picked up a couple of tenths on a single lap. The Kumho’s best lap now matched the Hankook’s.

It’s always tricky to run ten-tenths consistently on a track where an error could result in an agricultural experience. In fact, we find testing on a road course to be much more mentally taxing than autocross work.

Digesting Data

So, who won? The Hankook R-S3 definitely put down the best times in both performance venues, but all of these tires are very, very close. Unlike our previous tests, there isn’t a slow tire in this bunch. Whether a tire is “the best” really depends on its intended use.

Feel and temperature characteristics are now the biggest differences. Cooler weather? Shorter run/lap times? For those conditions, the Dunlop or Falken may be the best choice. Just don’t forget to use a water sprayer judiciously for additional cooling between runs.

Hot summer days or long on-track sessions? The Kumho or Hankook may be your best bet.

Is a “great communicator” high on your list? The Kumho and Falken are fabulous talkers, squealing with delight as they approach their limits. The Hankook and Dunlop, on the other hand, go about their business in relative silence. While none of the tires in this year’s test offer the razor-sharp response of the Yokohama Advan Neova AD08 tested last year, all but the Dunlop in this crop can deliver a consistently responsive feel.

It seems that we are in a golden age of extreme performance tires, where personal preference—and the occasional contingency offering—make the playing field interesting. This year’s batch offers performance on par with the fast guys from last year’s test: the Yokohama Advan Neova AD08, Bridgestone Potenza RE-11 and Toyo Proxes R1R.

Together, the class offers something for everyone. Which tire will you choose?

sources

Dunlop Tires:falkentire.com, (800) 723-2553 Hankook Tire: hankooktireusa.com, (800) 723-2553 Harris Hill Road: kumhousa.com, (800) HI-KUMHO SoulSpeed Performance: Join Free Join our community to easily find more Honda articles.

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