Type: Maximum-grip summer tire
UTQG: 180 AA A
»Low void asymmetric tread pattern with circumferential grooving for high cornering grip
»Ultra-fine carbon black compounding for maximum traction
»Ultra-wide tread contact with highly rounded shoulders for optimized footprint shape during high lateral loads
»Developed for quick autocross warm-up while maintaining racetrack durability
»With a Y speed rating, the tire has an optimum run temperature of 205 degrees Fahrenheit
»Rayon casing on selective sizes for added rigidity for handling and reduced heat
»Solid center tread rib for better steering response and straight line stability
High rubber-to-void ratio
»All sizes feature rim protector bars
»Asymmetric tread design for easy tire rotation
Test Mule: ’02 Audi S4 Quattro
Test driver: Jay Chen, technical editor, Modified Mag
Test track: The streets
Test condition: Both dry and wet
Over the years, we’ve seen some big changes in tires—namely, their technology and how they are marketed. The recent trend is in the extreme summer performance tire, which has become a niche market. As vehicle manufacturers continually create faster cars like the EVO and GT-R that come on specially developed super-sticky tires, tire manufacturers have realized the need for less expensive replacement options. That, combined with tire limitations from different grassroots racing sanctioning bodies, has spawned an entire line of new extreme performance summer tires that are just a few UTQG points away from full-on R-compound treated race tires.
This is a godsend for performance nuts and Street class racers who know just how important a good tire is and are willing to spend the money to regularly keep good rubber on their cars. We now have a wide selection of super high grip street tires at affordable prices and in a wide selection of sizes.
Jumping into the super-stick fray (with other amazing tires like the Advan Neova, Falken RT-615 and Nitto NT05) is Kumho’s new Ecsta XS (KU36), which we tested on a tuned twin-turbo AWD Audi S4 sedan. The XS (pronounced “x-ess,” as in excess) supersedes Kumho’s current Ecsta MX as the top dog when it comes to sheer dry grip and uncompromising performance. UTQG rated at 180 AA A makes this tire a great choice for use in SCCA STS or Time Attack Street class competitions where tire wear ratings are limited to no less than 180 or 140 UTQG, depending on the class.
But just because the tire was designed for competition doesn’t mean that it’s not a good street tire. The XS’ performance on our street car was quite the opposite.
Aside from the obscene amount of lateral grip on most street surfaces, the XS is extremely well behaved on the street. There’s very little pattern noise (something you wouldn’t guess based on the huge aggressive continuous tread blocks on the shoulders). Even with the larger center circumferential tread rib (which help on center feel and initial turn-in, but can cause tracking issues on grooved roads), we saw almost no tracking issues in well worn streets and highways. Sidewall construction is also relatively soft, which takes the unnecessary handling edginess or harshness out of a street tire. This along with the low noise makes for a very comfortable commute even compared to the high-end Michelin Pilot Sports 2s that the Audi originally came on. The rounded shoulder profile is a good match for the compliant sidewalls as it maintains a consistent contact patch (consistent lateral grip characteristics) when the car rolls hard into a turn.
We also really liked how little warm-up it took to get these tires to start generating grip even on a chilly morning commute. This makes the XS all that more usable on the street because you don’t have to beat on the tires just to get them sticky. And once sticky, getting loose on the street will take some excessively fast or stupid driving skills.
But the large tread blocks and super stick tread compounding does lose some of its initial turn-in feel in wet conditions. Like any tire of this design, wet grip is limited and driving stupid in the presence of standing water isn’t recommended. If it’s wet and cold, driving should be reeled back to a conservative pace. Tread wear will also set in faster than what you’re use to on an UHP tire. But that’s the trade-off. So if tire life is a priority, this isn’t the tire for you. But if you live in a dry, warm climate and R-compound grip with reasonable pricing without the tire hum and jouncing hard ride is your game, Kumho’s Ecsta XS will be a great fit. Fitments are limited so far, but sizing ranges from the standard 205/50R15 autocrosser special to a monstrous 345/30R19 that probably only fits on an Italian exotic.