Types of P Valve


1. Dual P Valve

The dual P valve is used in diagonal brake piping in FF vehicles. Basically, it may be considered as a pair of P valves operating side by side. Each of the two P valves operates in the same manner as an ordinary P valve.

2. Proportioning & Bypass Valve (P & BV)

The P & BV plays two roles. Firstly, it acts as an ordinary P valve. In addition, if the hydraulic circuit for the front brakes fails for any reason, it deactivates the P valve function. (Even if the master cylinder hydraulic pressure increases, the same pressure is transmitted to the rear wheels.)

3. Load Sensing Proportioning Valve (LSPV)

The LSPV is a device that is basically the same as the P valve, but it can adjust the P valve split point in response to the load applied to the rear tires. The LSPV prevents the rear brakes from over braking, locking up, and slipping, and also makes it possible to obtain a large braking force when the rear load is large. This is widely used in vehicles such as trucks, which the load balance applied to front and rear wheels change greatly when the vehicle is loaded and when it is unloaded. The load is detected by a load sensing spring located between the rear axle housing and the frame (or body). The split point can be adjusted by adjusting the spring strength. Sometimes a dual LSPV is used for diagonal piping in FF vehicles.

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