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Why do crossply tyres develop flatspots when I leave my car parked for a few days?

As the vehicle travels along, the tyres rotate and flex. This action generates heat within the casing of the tyre as the cords move. When the vehicle stops, the weight of the car presses down in one place and the tyres cool down, this can sometimes cause the tyre to set or develop a temporary flat spot. During the next drive the tyre warms up again and the process is repeated. To stop, or significantly reduce this cycle, raise the tyre pressures by three psi. This reduces the flexing and therefore reduces the heat generated.