A braking arrangement for a vehicle includes a source of compressed air, a drive axle for the vehicle, a brake associated with the drive axle and connected to the source of compressed air by an air line, an operator controlled valve in the air line between the source of compressed air and the brake, a proportioning valve in the air line between the operator controlled valve and the brake. A compressor is driven by the drive axle or a drive shaft of the vehicle and has an outlet connected to a control port of the proportioning valve.