Cycle News - Archive Issues - 2000's

that don't work well in print - well, maybe in Hustler. Anyway, my trip got off to a bad start, and I was really embarrassed, but it was almost worth it to see how hard editor Paul Carruthers was laughing at my mistake. When I finally arrived in Virginia the next day, the Dunlop staff took a couple of well-deserved, fun-spirited jabs at me as well. Hey, what can you do? Dunlop had invited members of the motorcycle press to Virginia to sample their new D208ZR tires at Virginia International Raceway (VIR), while also logging some serious street miles on those same tires in Tennessee - in conjunction with the Honda Hoot, which was taking place in Knoxville. What good is a l65-horsepower Kawasaki ZX-l2R, or a l45-horsepower Suzuki GSX-RlOOO, if you can't get the power to the ground? What good are six-piston calipers, with giant, twin 320mm rotors, if you can't keep the front wheel in contact with the road? These are the dilemmas facing the sportbike-tire manufacturers today. Not only do they have to make their tires meet the high-performance demands of modern sportbikes, but they have to meet those demands under every conceivable type of weather condition - from sweltering heat to pouring rain. Dunlop could have introduced its new tire to us by simply taking us on an extended street ride, but they were so confident with the level of abuse that their D208ZR could take that they let us torture countless sets of them on the racetrack. The bikes we rode consisted of a wide variety of sportbikes from the four Japanese manufacturers, and Ducati. Just for grins, here's the list of bikes that were available for us to ride: Ducati 748S; Honda CBR600F4i, Interceptor, and RC5l; Kawasaki ZX-6R, ZX-9R, ZX-l2R, and, on the street ride only, the new ZZRl200; Suzuki GSX-R600, and GSX-RlOOO; Yamaha YZF-R6, YZF-Rl, and FZ-l. The past lO years of sportbike development have really pushed the demand put on tires to an all-time high. Not only has streetbike power output exceeded what racebikes produced lO years ago, but braking forces and handling capabilities have increased dramatically as well. As sportbike wheelbases shrink, and geometry gets steeper, with power and braking capabilities where they are, the stresses on tires get harsher and harsher. Another problem is that the consumers are also becoming more and more demanding. Not only do they want a high level of performance, they keep asking for better mileage. RACETRACK IMPRESSION It always takes a while to get up to speed at a new track. The process consists of trying to learn where the corners are, figuring out the proper lines, and then finally starting to add some speed. After a few sessions, I started to get accustomed to VIR and was thrilled to be riding on such an entertaining and demanding track. The coolest thing about VIR is the elevation changes that are encountered throughout a lap, not to mention a few blind comers, and plenty of camber changes. Once I was up to speed, I was able to concentrate on the tires and was very impressed with their performance. Not only were they stable and compliant, they offered an excellent amount of grip - especially for a tire that was never intended for the racetrack. Andrew Trevitt, from Sportrider magazine, and I made it a point to go out together on similar bikes all day, just so we would have someone else to play with. The 600cc bikes were not only the easiest to ride on the tight and twisty track, but they dealt with the level of grip exceptionally well. We had our own little Supersport race going for a while. Another key ingredient to the torture test was the fact that the morning track temperatures were fairly high. Bikes like the GSX-RlOOO and There's a long list of ingredients that go into the construction of a tire. According to Dunlop, a tire like the D208ZR is actually a lot more complicated to make than a race tire because it has much broader operating parameters. Here are the major elements that went into the D208ZR. Carcass The D208ZR features a new carcass design in which new and innovative construction techniques were applied. Dunlop wanted the tire to not only have a stiff carcass, they wanted it to remain compliant at the same time. To achieve this, they created a new process called Carcass Tension Control System (CTCS). The new reforming process builds up intemal tension in the tire during the molding process in order to build a stiffer shoulder area, for better grip and stability. This method also allows the crown area of the tire to be less stiff and more compliant for straight-up riding. All of this was accomplished without adding extra plies (layers) to the tire that would just add weight. The new rear D208ZR weighs 1.7 pounds less than the D207ZR, and the front weighs 1.2-pounds less, which should enhance handling by reducing the unsprung weight. ProfIle The D208ZR's progressive profile has also been reshaped in an effort to initiate quicker tum-in compared to the D207ZR. Additionally, the profile allows the tire to create a larger footprint (contact patch) on the road at maximum lean angle. The rear-tire profile was designed to mimic the D208GP race tire in an effort to create quicker tum-in on rims that have grown wider and wider over the last 10 years. Tread Pattern The new tread pattern incorporates the next generation of the cosecant groove shape. This yields a consistent ratio of rubber-to-groove area at all lean angles, as the contact patch transitions from vertical to maximum lean angle. Near the shoulder of the tire, the grooves taper down to a minimai degree, so while at maximum-lean angle, the amount of tire to surface contact is very high. On the crown of the tire, the rubber-to-void area is increased for wet-weather riding. Construction One of the key elements we mentioned above was the (CTCS) molding process. The new rear tire features Dunlop's Jointless Belt (JLB) construction, which features a circumferentially wrapped aramid belt, as opposed to the cut-breaker construction on the race tire. The front features a cut-angle breaker and a two-ply carcass construction. Compound The D208ZR has much more race-tire technology added to the mix than the predecessor, the D207ZR, had. Not only is the D208ZR's compound much stickier than the tire it replaces, it was designed to have excellent mileage as well. The front tire has specially formulated styrene butadiene rubber (SBR), a polymer-based compound to lmprove wetroad grip and handling. The rear has the high-grip SBR compound with the latest finegrain carbon black combined with silica to enhance grip and promote wear resistance. The new compound is designed to promote quick warm-up as well. ZX-9R have more than enough power to spin a race-compound tire on the track, let alone a true street tire like the D208ZR. Yes, I was painting blackies on the corner exits - lots of them - but that was to be expected, and the tires handled the conditions extremely well. I expected the D208ZR rear tires to struggle a bit on the big bikes - and was expecting the front tires to do the same. However, I was pleasantly surprised with the performance of the fronts on all of the bikes. I don't recall having an out-of-the-ordinary slide at VIR all day. In addition, the tires performed very well under the extreme braking for turn one at the end of the long front straight. They offered excellent stability and compliance under braking, while also giving good feedback. One specific thing of note: When I rode the 2002 Yamaha Rl at the Construction and Profile Carcass: 2Plies (Nylon) Breaker: 2Cut(Aramid) Profile: Single Radius Carcass: Mono-Ply(Rayon or Nylon) Belt : JLB(Aramid) Breaker: 1Cut(Rayon or Aramid) Profile: Single Radius U Y II: I B n e _ s • JULv31,2002 51

• Cover