BENDIX BP-R1 Service Data

®
Bendix BP-R1 Bobtail Proportioning Relay Valve
® ®
Control
Exhaust
Supply
Figure 1 – Bendix BP-R1
®
DESCRIPTION
The Bendix BP-R1 bobtail proportioning relay valve
® ®
is a combination of two individual valves in a single
housing. The lower portion, or body, of the valve contains
a "standard" service brake relay valve which functions as
a relay station to speed up brake application and release.
The upper portion, or cover, houses a brake proportioning
valve which reduces normal service brake application
pressure when the tractor is not towing a trailer.
Used in tractor air brake systems only, the BP-R1 valve
is installed in place of a standard relay valve. It functions
as a standard service relay during operation of a tractor-
trailer combination. During bobtail tractor operation, the
BP-R1 valve improves controllability and reduces stopping
distances by reducing air pressure to the rear actuators/
chambers, whose axle load has been greatly reduced.
While the BP-R1 valve can incorporate various crack
pressures to accommodate specific applications, the
standard is 4 psi.
Service
Delivery
Bobtail Proportioning Relay Valve
®
Service
Exhaust
Designed for frame or cross member mounting, the BP-R1
valve is furnished with a mounting bracket which is attached
to two of the four cover cap screws. Replacement valves
are furnished with a universal mounting bracket, which
allows the valve to replace most standard relays.
All air connections on the BP-R1 valve are identified with
cast, embossed letters for ease of installation. The letter
identification and air line connections are shown below
for reference.
OPERATION
BP-R1 Valve Air Connection
Supply (to reservoir)
Delivery (to brake actuator)
Service (brake valve rear axle
service delivery)
Control (to delivery of trailer supply
valve)
Control
Vent
Supply
Embossed
Identification
SUP
DEL
SER
CON
1