Description

Overview

This bobtail brake relay valve manages rear axle brake pressure so tractors and prime movers stay stable when operating without a trailer. It combines relay and proportioning functions in one body so the service brake signal reaches the rear chambers quickly and in a controlled way. As a result, the driver keeps better pedal feel and control during bobtail operation.

Features

The BP-R1 style bobtail brake relay valve uses a two-stage internal layout to handle both full combination work and bobtail running. In normal combination mode it behaves like a standard service relay valve and delivers full line pressure to the rear axle. During bobtail running it automatically reduces delivery pressure so the light rear axle does not lock too easily. Additionally, clearly marked port locations simplify installation checks and future servicing.

Specifications and Materials

This valve includes a 1/2″ NPT supply port, four 3/8″ NPT delivery ports, a 1/4″ NPT service port, and a 1/8″ NPT control port so you can integrate it cleanly into common tractor air brake layouts. The crack pressure is set around 5.5 psi to balance response and stability for typical highway tractors. Part number: AB8465P. Housing and internal hardware follow standard heavy vehicle air brake construction so the valve suits demanding fleet work. For more detail on how a bobtail proportioning relay valve behaves in an air brake circuit, refer to this Bendix based air brake technical guide

Compatibility and Fitment

This cross-reference listing means this valve is a suitable replacement for the part numbers and applications shown. Some changes in air line plumbing may be required. 065146, 106931, 108184, 108184x, 108230, 108230x, 108505, 108505x, 109041, 109041x, 109065, 109065x, 109067, 109067x, 109105, 109105x, 65146F3HS2A449BA, 6814291344, 20QE4108M, WA65146, 1622154C91, 2026144C91, 802675, 802681, 802795, 802796, 3918392, 8064515, BPR1

Compliance and Safety

Fit this bobtail brake relay valve only to vehicles with compatible air brake designs and system pressures. Always isolate and drain the air system before removing or installing valves, then tighten fittings to the recommended torque so leaks do not develop under load. After installation, carry out a full leak test and a static brake test, then perform a controlled road test so you can confirm stable bobtail behaviour and correct relay response.

Trailer Applications

This bobtail brake relay valve suits tractors and prime movers that work in both linehaul and local distribution where frequent coupling changes occur. It particularly helps vehicles that run light over the rear axle for long distances between trailers, since the proportioning function reduces the chance of premature rear wheel lockup. In addition, fleets that move between highway and yard work gain more predictable service brake feel during solo operation.

Cross-reference and Suitability

This part cross-references to or suits the following equivalent part numbers and compatible alternatives:

Why Choose ICS Trailers

ICS Trailers focuses on hard working heavy vehicle parts, so you can match a bobtail brake relay valve to your fleet with confidence. Our team checks cross-reference data and port layouts so you receive a valve that suits common tractor installations and helps keep downtime low. Browse Air Brake Parts at ICS Trailers in the Air Brake Parts category