Tread temperature will vary depending on ambient and track temperature, the type of circuit, and the type of car. The temperature should be within a range of 160 to 220 degrees when measured in pit lane. Optimum grip level is at 180 to 200 degrees.
A probe type pyrometer is recommended for temperature measurements, and a consistent technique must be used. Check the tires in the same location (inside, middle, outside) and in the same order (LF, RF, RR, LR) each time the car comes to pit lane. The data should be recorded as follows to make it easier to interpret.
Depending on the width of the tire, the inside tread temperature should be 10 to 20 degrees hotter than the outside. If the inside is too hot, camber may need to be reduced. If the outside is too hot, camber will need to be increased, or inflation pressure will need to be increased to prevent the tire from rolling over on the outside shoulder.
If the front tires are hotter than the rear tires, it may show an understeer condition, and if the rear tires are hotter than the front tires, it may show an oversteer condition. This isn’t the case for all types of vehicles. The front tires on FWD cars are usually always hotter, and the rear tires on high horsepower RWD cars may be hotter due to wheel spin.
The tires should be relatively new when using tread temperature data to interpret car set up issues. Tires with a worn shoulder may give a misleading temperature spread across the tire because the thin area doesn’t hold as much heat as thicker areas.