The following article was from Cycle World September 2010 titled “Round and Black” by Kevin Cameron.
Competition is expensive and money is scarce. That pushes racing toward spec everything. AMA Pro American SuperBike runs on spec Dunlop slicks made in England. DOT tires for other classes are made in Buffalo, New York.
A provider of spec tires must first of all satisfy those it supplies that the same choices are available to all without reservation. The maker of a spec tire has an opportunity for development, using the data collected through a race series to steer improvements. Or the maker may elect to simply supply well-understood conservative compounds and constructions, taking the benefit of its series participation in public relations. It’s all a matter of money.
Naturally, there cannot be just one spec tire because everything changes from one track to the next, and riders vary in their manner of using tires. Therefore, a range of tires is planned to suit the special conditions for each event, designated soft, medium, and hard. For peak grip, a given rubber compound must operate in a limited temperature range, which is why you see every team wrap its tires in electric warmers when they are not on the track. The “soft” tire reaches peak grip at a temperature somewhat lower than that of the “medium” and so on. This allows the teams to find a tire that their rider’s style and machine setup can bring to its best operating temperature on the track.
Each rider has a tire allocation – so many fronts of the various hardnesses and so many rears. Practice must be planned to leave enough o the final chosen tires for the race.
There is a long-running trend toward lower inflation pressure because this increases footprint area, which, with softer rubber, can generate greater grip. Radial tires naturally run cool, and recent developments have allowed less rubber to be used, which allows still cooler running. This “temperature margin” is used to allow a tire to tolerate the increased flexure of operature at lower pressure. The narrower front Dunlop SuperBike tire used during the June test at Barber Motorsports Park was given a range of 32-35 psi and the much-larger rear 21-24 psi. If a rider chooses a low pressure for its grip potential, he must balance that gain against possible earlier loss of tire properties as the greater flexure makes the tire run hotter.
There are irreversible changes in racing rubber during use. When a race starts, tires heat up and reach peak grip in about three laps. After that, a variety of things can happen. In MotoGP, riders speak of “a first step” in grip loss and then a second, but fastest laps are often achieved late in races. Certainly, much progress has been made to make this possible. I was told at Barber that the Dunlops on the Team Cycle World Attack Performance Yoshimura Suzuki should do 24 laps. This is a great improvement over the 1990s, when a 500cc World Champion Mick Doohan spoke of “just sliding around” for the last 10 laps of GPs. Tire conservation remains crucial in racing.
Tires are central to performance. Most of the real gains in production and racing motorcycle capability have come from tires.