You can try and soak them in ice water for a couple of hours and this will shrink them. Be sure you let all the air out of the tire and replace the valve stem. This will hardend them for a while, but I'am afraid it wil only be temporary.
Depending on what kind of race, the tires get worn quickly during the race.
A burn out will ruin tires on race cars by burning up the rubber. The rubber of the tires will get worn from the friction of the pavement causing the tires to tear.
Sulphur, in a process called vulcanization.
Tires are changed during an auto race because the tires get worn down by the track. It is safer to have good tires than to have tires that are worn down that could blow apart and cause accidents.
It is nitrogen.
Nitrogen
The track and tires are both sprayed with a special solvent compound.
slick tyres are used.
Slicks.
nitrogen
The tires of the car
GoodYear