Tire softener treatments are designed to soften tire rubber, usually by using special solvents. Some race car drivers believe tire softening increases tire traction and results in reduced lap times.
Tire softener is either used to soak the tread or applied to the tire surface, according to the magazine "Stock Car Racing." The solvents evaporate quickly, so merely wiping softener onto the tire is not very effective.
Deeper penetration by soaking is thought to provide better results. The tires may be placed in bags afterward to slow the evaporation of the softener. Soaking is not legal at all racetracks, although the practice is common.
There are safety concerns about the flammability of the solvents, according to "Stock Car Racing" magazine. Excessively soft tires may also result in tire failure on the track.