Proportioning Valve

Fig. 23 Type 1, Combination Valve:

Fig 2 Brake Warning Switch / Hold Off Valve (Cut Away View):

NOTE: This valve is part of a combination valve. See Application and ID.

The proportioning valve section transmits full input pressure to the rear brakes up to a certain point, called the split point. Beyond that point it reduces the amount of pressure increase to the rear brakes according to a certain ratio.
- On light pedal applications, approximately equal brake pressure will be transmitted to the front and rear brakes.
- At higher pressures, the pressure transmitted to the rear brakes will be lower than to the front brakes to prevent premature rear wheel lock-up and skid.

If hydraulic pressure is lost in the front brake system, rear brake system hydraulic pressure moves the brake warning switch piston and opens a bypass in the proportioning unit allowing full rear brake hydraulic pressure.