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Automann · Air System
170.065145
In stock · ships from Knoxville
This is a BPR1-type bobtail proportioning relay valve for heavy-duty truck air brake systems.
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Verified fitment for 2 applications
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Designed for any heavy-duty tractor with air brakes that needs bobtail brake modulation; verify port sizes (1/2" NPT supply, 3/8" NPT delivery, 1/8" NPT control, 1/4" NPT service) and crack pressure match OEM specification.
Part data verified against 5 catalog sources
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It combines a standard relay valve (lower section) with a proportioning valve (upper section) to automatically reduce air pressure to the rear brakes when the tractor is operating without a trailer (bobtail mode). By lowering rear brake force, it prevents wheel lockup and improves stability and control during solo tractor operation. The valve opens at a crack pressure of 4.0 PSI and is replaced when it fails to properly modulate pressure, causing uneven braking or rear wheel lockup while bobtailing.
Part Number: 170.065145
BPR1 TYPE PROPORTIONING VALVE 4.0PSI
Unit: ea
Dealer: Knox Trailers
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Parts commonly needed alongside air system
