Pirelli North America Racing...
Pirelli North America Racing Manager Cristoph Knoche.
Few aspects of riding technique are as clouded with the dark specter of myths, old information-or just plain bad information-than how to warm up new tires. In fact, many of us, me included, still use the misleading terminology of "scrubbing" in new tires, which wrongly implies that the surface of the tire itself needs to be scrubbed or abraded to offer traction. While this may have been the case long ago when manufacturers used a mold release compound, it most definitely is not the case today.
To clear up the issue of how to ride on new tires, we cornered Cristoph Knoche, the Racing Manager for Pirelli Tire North America's Motorcycle Division. Knoche has been with Pirelli for 13 years, working with the company's R&D department while involved with World Supersport, where Pirelli won the World Championship with Fabien Foret while battling against the other brands prior to the series adopting Pirelli as the spec tire for World Supersport and World Superbike. More than just a racetrack technician, Knoche also has first-hand experience with the prototyping process and development of special racing tires.
First off, Knoche quickly dispatched the old wives' tale that the surface of the tire needs to be scuffed or roughed up to offer grip. "Maybe it's coming from the old days when people were spraying mold release on the tread when the molds were maybe not that precise," Knoche speculates, "and the machinery was not that precise. But nowadays molds are typically coated with Teflon or other surface treatments. The release you put in there (in the sidewall area only, not the tread) is for like baking a cake, you know, so that it fills all the little corners and today that is done more mechanically than by spraying. The sidewall is important because you have all the engraving in the sidewall [with tire size, inflation pressure and certifications] and that you want to look nicely on your tire, so that's why we still spray the mold release there."
Knoche discusses tires with...
Knoche discusses tires with Attack Kawasaki's Chaz Davis (right) and Richard Stanboli.
The next myth we see perpetuated nearly every time we watch the warm-up lap to a race. Riders begin weaving back and forth in apparent attempt to scuff the tread surface (which we've already discounted) and generate heat. The reality is that, according to every tire engineer that I've asked, there are far more effective ways of generating heat in a tire that are also much safer. Rather than weaving back and forth-which does little in the way of generating heat but does put you at risk asking for cornering grip from tires before they're up to temperature-you're far better off using strong acceleration and braking forces, and using them while upright, not leaned over! Acceleration and braking forces impart far more flex to the tire carcass, which is what generates the heat that then transfers to the tread compound as well (you often see Formula 1 cars weaving violently back and forth because automobile tires operate on a horizontal plane, so they have and use significant sidewall flex to generate heat).
All I can say is that you should trust the educated opinion of tire engineers over the old habits and superstitions of even the best racers. That said, I still-out of habit-occasionally catch myself weaving out of the pits on fresh rubber before chastising myself and then applying heavy yet smooth acceleration and braking forces into the tire while keeping the bike relatively upright.
If you're a racer, or a serious enough track-day rider to have tire warmers, Knoche recommends that you have them on the bike for a full hour to get not only the tread surface of the tire, but also the entire carcass and sidewall section, up to temperature as well. "With modern compounds," Knoche explains, "there are a lot of waxes and oils and (we) have to get them really to temperature. We suggest to get them up to around 165 degrees Fahrenheit. Because what happens is you have to warm your tire not only on the surface but what we look for is touching the wheel and you want that a little bit more than hand warm."
Knoche and another Pirelli...
Knoche and another Pirelli tire engineer confer after a practice session.
In addition to warming tires up before the session, Knoche also recommends that riders coming off the track get the warmers back on to prevent the tires from cooling and going through another heat cycle. "Even with the tire on the warmer all the time," warns Knoche, "it takes about two laps to get to the good compound underneath, a little bit."
It should be noted, as well, that unlike many tire brands that give suggested cold tire pressures, Pirelli prefers to set tire pressures after the tire is up to temperature (165 degrees F on a warmer or after 10 minutes of lapping the track). Knoche says that pressures vary slightly depending on track conditions and rider preference but that the Pirelli engineers prefer to run from 32 to 34 psi in the front and from 28 to 30 psi rear. They like to see between a 3 to five pound rise in pressure from the initial cold tire to one at 165 degrees or above.
It might follow that suggested cold tire pressures would start 3 psi below the pressure listed above, but Knoche wasn't comfortable making that suggestion. Instead, he recommends, as many tire engineers do, that riders, "contact our technical support people."
Many years ago I recall a coworker at Motorcyclist magazine telling me that it could take as much as 100 miles for a tire to truly break in and offer good traction. I doubted that it was true then and it certainly isn't true today. Knoche reaffirms that there's no need to believe that old myth that often left typical street riders riding away from the dealership on new tires literally white-knuckled with fear of the "treacherously slippery" tires.
"I would say nowadays if the surface looks like new-as long as you don't have contact cleaner on, no soapy water (often used by tire fitters to help slip the bead over the rim) or oil-there should be no concern," said Knoche. But that isn't clearance to simply go for it, either. "For sure a new tire, especially if you change the brand or even get a different production lot, it can be slightly different," Knoche said. "So I think that's more the concern people should have. Maybe with a new set of tires that's a new experience. Get the experience; it's like riding in a brand new car, you don't race around the first corner because you don't know what's going to happen."
Finally, there is the aspect of using race tires on the street. Interestingly, Knoche says Pirelli's street and DOT race tires should come up to temperature equally quickly and at no time does the race compound offer less traction than that of the street tire. However, this is not a statement that we feel can be safely applied to all brands of tires, as we've heard differently from tire engineers (not marketing managers) from other companies regarding their specific brand. Regardless, there are plenty of other reasons not to run modern DOT race tires on the street, not the least of which is tread life that can be as short as 300 miles of aggressive riding! That's a cost of well over $1.00 per mile. Such are the compromises required to run at the front of the pack in AMA Pro Racing competition.
"That's why we developed the Diablo Corsa III," said Knoche. " This tire has, in the rear, three compound sections. The center is a street compound but on the side you have about one and half inch, probably, of our race compound, which gives you a little bit more fun." Take a look at any competitive DOT race tire and you'll note the scarcity of tread grooves in general and the total lack of them anywhere near the edge, or shoulder, of the tread. Even for track day riders that may face damp or wet riding conditions without the luxury of a spare set of wheels with wet weather tires mounted up, Knoche recommends the equivalent of Pirelli Diablo Corse IIIs, "so that we don't have to change to intermediate or rain tires because they're designed for the street.