1
SD-03-1067
Bendix
®
BP-R1
™
Bobtail Proportioning Relay Valve
DESCRIPTION
The BP-R1
™
bobtail proportioning relay valve is a combina-
tion of two individual valves in a single housing. The lower
portion, or body, of the BP-R1
™
valve contains a “standard”
service brake relay valve, which functions as a relay station
to speed up brake application and release. The upper por-
tion, 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.
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 BP-R1
™
valve to replace most standard
relays.
All air connections on the BP-R1
™
valve are identifi ed with
cast, embossed letters for ease of installation. The letter
identifi cation and air line connections are shown below
for reference.
BP-R1
™
Valve Air Connection
Embossed Identifi cation
Supply (to reservoir)
SUP
Delivery (to brake actuator)
DEL
Service (brake valve rear axle service delivery)
SER
Control (to delivery of trailer supply valve)
CON
FIGURE 1 - BP-R1
™
BOBTAIL PROPORTIONING RELAY VALVE
SERVICE
SERVICE
CONTROL
EXHAUST
SUPPLY
DELIVERY
SUPPLY
EXHAUST
CONTROL
