What's the use of a car burnout for a race?????????

In drag racing, you do a burnout after entering the water box. It's only a useful technique for drag slicks or drag radials. Standard radial street tires will see virtually no benefit, as the rubber doesn't warm up, it just breaks apart. Most people do big burnouts with lots of smoke to show off, but in reality its overkill and just wastes tire. The real reasons people do it are two fold. First, is it clears any debris off the tires, and burns off the old rubber on the outside which might be slightly hardened from exposure to air and the elements, especially the first p of the year after they have sat in the garage over the winter. The second reason was touched on by others...to heat the tire up. When drag specific tires are heated up, the rubber becomes softer and very sticky. When combined with the rubber on the racing surface and the traction compound applied, it gives a tremendous amount of grip, necessary for high horsepower cars to launch hard.