Pro Advice on Dirt Tires

* Groove Widths: On some tracks, you can groove the tires twiceas much with a narrow groove, or half as much with a wide groove, andaccomplish the same thing. It depends on the track surface and howabrasive it is, or if it contains rocks that will tear up the tire. Youdon't want a lot of grooves on a rocky or highly abrasive track. Widergrooves stand up to these harsher conditions better.

* Groove Shapes: There are three basic shapes used in grooving:square, V, and sipes. Square grooves are the same width through itsentire depth. V grooves start out wide at the top and taper to nothingat their bottom. Sipes are thin slits cut by installing the blade upsidedown in the holder and using the separate ends of the blade to cutslices in the tire.

* Groove Angles: The angle at which grooves are cut determineshow much of the edges are exposed to the track when the car is invarious degrees of slide. The more the car will be sideways, the moreangle should be put into the grooves. As a dirt car travels around thetrack on a given line, the body is actually pointed toward the infieldin varying degrees. If the driver is consistent, you can determine anangle for the tire grooves that will work best for your combination.

* Grooves and Heat: Some tracks naturally put a lot of heat intoa tire and can actually cause the tire to melt or blister. On thesekinds of tracks, grooving helps cool the tire. The grooves (and sipes)help move air across the tire's surface, which keeps the treadtemperatures down. Grooving also produces more surface area, which helpstransfer heat out of the tire to the air. To help a tire dissipate heatwithout weakening the tread blocks too much, cut grooves in the centerof each block instead of cutting all the way across it.

8. CHEMICALLY ALTERED TIRES

Race Tires America strongly discourages this practice as a method forreducing lap times.

They advise against: (1) chemical alteration of the tread carcass and ortread compound, such as tire "soaking;" (2) use of tread softener; or(3) the physical defacement (removing, altering, or covering) oftire-sidewall markings in any manner. Failure to comply with thiswarning could result in premature or catastrophic tire failure that mayresult in serious injury or death.

Tire manufacturers are obviously sensitive to the liability of thispractice, but certain products on the market claim to help you reduce afew tenths off your lap times by softening the compound of your tire.Some tracks and sanctions have outlawed "soaking," while others stillallow it or turn a blind eye. While the practice of soaking tires iscommon, you should evaluate the level of risk you're willing to endureto possibly pick up a few tenths versus the chance of an untimely tirefailure.