The continuous rotational movement of a geared motor unit is converted into a reciprocating movement by an oscillating bearing supporting a telescopic arm. This arm transmits its movement to a carriage moving on two rails attached to a streamlined frame. The carriage simulates the action of a vehicle axle. It carries two wheels, each mounted on a spindle articulated on a pivot. The mean plane of each wheel passes through the longitudinal axis of the specimen at zero orientation of its pivot. The pressure action of each tyre on the material is obtained by the loading of a cylinder acting on the support of the specimen guided on the frame. A heating system with air circulation and regulator keeps the temperature constant during the test.