1-15. BRAKE SYSTEM (CONT)
Figure 1-24. Brake System (Cont)
The foot control valve is operated by the brake pedal (5) and receives pressurized air from both the primary and
secondary air tanks. The foot control valve is a dual activation design, with one set of ports supplying air to the front
brakes from the secondary air tank and another set of ports supplying air to the rear brakes from the primary air tank.
The plumbing between the primary and secondary air tanks is designed to allow controlled braking in the event of a
failure in either the primary (rear brakes) or secondary (front brakes) brake circuit. A booster valve (6) is incorporated
into the primary brake circuit to provide a more rapid braking response. Air from the booster valve is supplied to the
load sensing valve (7) which, in turn, controls air delivery to the relay valve (8). The load sensing valve is mounted
on a crossmember and connected, by a spring and cable, to the load averaging channel. This arrangement of the load
sensing valve and load averaging channel provides a mechanical anti-lock feature to the rear brakes by sending less
air to the rear brakes when the vehicle is not heavily loaded. The relay valve is used to provide the operator with
quicker brake response. An inversion valve (9) redirects air from the secondary brake circuit to the primary brake circuit
in case of loss of pressure in the primary brake circuit. This feature allows control of the spring brakes and prevents
early rear brake lock-up.