The Load Sensing Proportioning Valve (LSPV) is used on vehicles equipped with the standard (non-ABS) brake system. The LSPV consists of a lever and a load sensing spring. The spring senses the variations in the vehicle height proportional to load weight. A plunger/valve mechanism inside the LSPV performs the hydraulic pressure modulation.

A chamber with a fail-safe piston monitors the front hydraulic brake pressure. In case of front hydraulic brake pressure loss, the fail-safe piston releases the plunger/valve mechanism, canceling hydraulic pressure modulation. This allows full master cylinder hydraulic pressure to apply the rear brakes.

The LSPV assembly is bolted to the vehicle frame. The LSPV lever is connected to the rear suspension upper arm by a bracket and load sensing spring.

As the vehicle is loaded, the distance between the rear suspension axle housing and the vehicle frame decreases. As the LSPV load sensing spring length changes, it applies force to the LSPV lever. The lever actuates the plunger valve inside the LSPV assembly. This results in increased rear brake hydraulic pressure proportional to the vehicle loaded weight.

The proportioning valve is used on vehicles equipped with the Antilock Brake System (ABS). Outlet pressure is controlled to the rear brakes after a predetermined rear input pressure has been reached. This allows for smooth braking action and reduces the chances of rear wheel lockup during normal braking.

The proportioning valve has a bypass feature which ensures full system pressure to the rear brakes in the event of a front brake system failure. In case of a rear brake system failure, full system pressure is delivered to the front brake system.