Dunlop is one of those companies that thrives on competition. But as the spec tire mentality began to take over racing across the world, Dunlop found itself having to join the ranks last year by taking on the spec tire contract for AMA racing in the U.S. The company soon discovered that in order to adequately supply all the tires for each race, it would need to produce the DOT race tires at its Buffalo, New York, manufacturing plant instead of shipping them over from England as in years past.
The first year was not without its teething issues. AMA racers complained that tire performance wasn't up to Dunlop's usual lofty standards, and the company quickly came out with a revised version in the middle of last season that quelled most of the complaints. The competitive streak honed from years of dominating the roadracing scene in the U.S. meant that Dunlop wasn't about to just stand pat, however-leading to the latest version debuting at this year's Daytona AMA races.
The new Sportmax D211 GP-A is result of a significant investment on Dunlop's part to remain as the dominant brand here in the States-both in racing and motorcycling in general. The company recently installed two multi-million-dollar tire manufacturing machines that use the same basic design and state of the art technology as the Dunlop UK equipment that previously supplied the DOT race rubber, but with the added capability of constructing even more shapes and sizes of tires to meet future motorcycle designs. In fact, Dunlop's Buffalo facility is the only motorcycle tire manufacturing plant in the U.S. Utilizing the same N-TEC hybrid construction from the dominant '08 D211 GP race tire made in the UK that optimizes the compliance benefits of cross-ply belt design with the stiffer jointless band (JLB) architecture, the new Sportmax GP-A rear has a nylon carcass overlaid with two nylon cross-ply belts, and the continuously wound circumferential JLB aramid-fiber belt on top. The front tire has two nylon carcass plies and two aramid cross-ply belts. Both tires use a continuously wound hex bead that-compared to conventional round or square-shaped beads-demonstrates improved feel and predictability as the tire nears its cornering limit.
The steeper shoulder profile...
The steeper shoulder profile of the new D211 GP-A rear tire is demonstrated in this diagram.
The nylon material used in the belts is also stiffer, which allows for steeper sidewalls and an entirely different tire profile. Christened IRP (Intuitive Response Profile) by Dunlop-first used on the Sportmax Q2 in '09-the steeper sidewall angles improve steering and provide a more linear response to various steering inputs, along with offering better feedback and overall stability. But the biggest benefit is a larger contact patch when leaned over; the D211 GP-A footprint peaks at approximately 50 degrees of lean, and is said to remain substantial up to 60 degrees, whereas the previous D211 version peaked at 40 degrees. The rear profile is visibly narrower and taller, while the front is slightly wider with a steeper tread drop on the shoulders.
Keeping with the N-TEC design, the rear tire features Dunlop's MT (Multi-Tread) technology with different tread compounds that are extruded simultaneously. First introduced in the Sportmax Q2 and also incorporated into the Sportmax Roadsmart, the MT technology combines the usual harder, cooler-running compound in the center for better straightline stability and wear with a stickier compound on the shoulders for better grip at moderate-to-maximum lean angles. In addition to significantly improved grip, stability, and durability, the ultra-fine carbon black and proprietary resin used in the compounds are also claimed to provide low warm-up time and better resistance to repeated heat cycles.
Of course, the proof is "on the pavement", and AMA racers have reported that the D211 GP-A tires are indeed far better than their predecessors. At the AMA Pro Superbike event at Auto Club Speedway in Fontana, nearly all racers-from the top factory pilots battling at the front, to the privateers on down the field-reported an average of just over a second a lap improvement over the previous generation Dunlops.
Contact your local Dunlop race tire distributor for compound, sizing, and pricing information.