Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/1209558
DUNLOP'S NEW DT4 DIRT TRACK TIRE P96 Feature sidewall, which give it a bit more compliance there. Still, it's pretty similar. The mold profile is basically the same as before, which means the tire itself, when mounted on a wheel, is almost identical in shape to the old tire. We did not want to disrupt the general feel of the bike with this new tire." The list of totally new elements is significantly longer and includes the most obvious change—to- tally new tread patterns front and rear. The front DT4's pattern bears some resemblance to the old tire, though there are only three grooves running circumferentially instead of five, with those grooves being straight instead of the DT3s mildly S-shaped ones. Dunlop says the grooves (and especially the arrow-straight centerline groove) help improve straight-line stability by not feeding any left- or right-directional forces into the chassis as the old tire did, which may have contrib- uted to front-end headshake at speed. The shape of the tread blocks, and especially those on the tire's shoulders, is different, as well, with the shoulder blocks having more leading-edge edge than before, which improves stability and grip while cornering. The rear has similarly shaped (yet larger) tread blocks on each shoulder (which employ the leading-edge edge character- istics of the front), though the center of the tire is vastly different, employing uniquely shaped center lugs that have been turned 90 degrees. "Turning these blocks perpendicular adds more biting edge during starts and while transitioning from leaned over to straight up on corner exits," says Bell. "They also have a lot of unique siping, which involved a lot of testing. At first the sipes were too deep and too numerous, which allowed too much tread-block flex and squirm, which allowed excessive heat and wear. But over time we got the balance between the number of sipes, their depth and their positioning just right. Back in the day, teams got pretty good at cutting their own customized sipes for use at particular racetracks. One pattern for cushion tracks, one for clay tracks, etc. It's like that scene in On Any Sunday! That's not allowed anymore, so we've sort of done it for them with the DT4." Dunlop did a ton of testing on the new tires during 2018 and 2019 at a varied selection of racetracks and with a handful or top-level riders, in- cluding Jared Mees, Johnny Lewis, Shayna Texter, Dan Bromley, Sammy Halbert, Davis Fisher, James Rispoli, Hayden Gillam, JD Beach, Taylor Napp and others. You can't change the rear tire without changing the front, and vice versa.