Load Compensator: Description and Operation

Loading Sensing Proportioning Valve (LSPV) Assembly:

DESCRIPTION
A Load Sensing Proportioning Valve (LSPV) is installed between the master cylinder and the rear brake hydraulic circuit on models without the Antilock Brake System (ABS). It modulates rear brake hydraulic pressure based on the loading state of the vehicle. The LSPV prevents the rear wheels from locking-up prematurely during heavy braking periods, especially when the vehicle is lightly loaded. Full hydraulic pressure (non-modulated) is available to the rear brakes in case of a loss in front brake hydraulic pressure.

Load Sensing Proportioning Valve (LSPV) Assembly (Sectional View):

OPERATION
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 perform the hydraulic pressure modulation. A chamber with a fail-safe piston monitors 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 then moves, actuating the plunger valve inside the LSPV assembly. This results in increased rear brake hydraulic pressure proportional to the vehicle loaded weight.