Gear belt tensioning apparatus is provided for controlling the tension in a gear belt for driving an internal combustion engine camshaft or the like. This apparatus includes a tension roller which engages directly with the gear belt and which is controlled by a temperature responsive control element. In order to accommodate for changes in temperature of the internal combustion engine, the control element is composed of a plurality of stacked bimetal dish-shaped spring members arranged in a cylindrical recess of an abutment fixed to the engine housing. These spring members are arranged in packets of four members each, which packets are then arranged so as to have the spring members of one packet facing in the opposite direction of the next adjacent packet of spring members.