Tyre warmers are designed to keep the tyres at optimum operating temperature. They plug in to the mains and are controlled by a basic thermostat. The trick is to find a temperature that delivers good grip on the banking without making the tyres so sticky that the rolling resistance is affected. The temperature choice is further complicated by rider weight, ambient temperature of the track environment and even the event that's being ridden. You often see riders swerving around on the track in an effort to keep heat in the tyres, but this is frowned on by the UCI, particularly after Miguel McSporran's death at the Mexico Olympics where he was tragically t-boned on the back straight by a rider from the Dominican Republic.