Proportioning Valve
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Proportioning Valve
O.K. Heres a dumb question for ya. Have any of you ever bypassed the proportioning valve on you trucks? My 1st truck I remember replacing the brake lines from M C to all 4 wheels. I was young & inexperianced. They were rotted & I just snapped them off and ran new ones. At the time I was unaware of the proportioning valve. I accidently bypassed it. This was way before this website was around. Now I know its there. But, I drove that truck for a year or 2 before I sold it & dont recall ever having a problem with the brakes. Was I lucky or is this valve not that important?
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
Bypassing the proportioning valve is probably one of the most unsafe things you can do. It performs three functions:
(1) Detects a breach in the front or rear braking circuit and shuts off flow to the offending end to maintain braking pressure in the event of a fluid leak.
(2) Delays pressure to the front brakes so that the rear brakes can make contact by the time the fronts make contact.
(3) Rations pressure between the front and rear braking circuits, so that the front brakes, who do more work, have higher braking pressure than the rears.
Do not bypass the valve under any circumstances. When you replace a brake line, always follow it to see where it starts and ends.
(1) Detects a breach in the front or rear braking circuit and shuts off flow to the offending end to maintain braking pressure in the event of a fluid leak.
(2) Delays pressure to the front brakes so that the rear brakes can make contact by the time the fronts make contact.
(3) Rations pressure between the front and rear braking circuits, so that the front brakes, who do more work, have higher braking pressure than the rears.
Do not bypass the valve under any circumstances. When you replace a brake line, always follow it to see where it starts and ends.
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So it sounds like I was VERY LUCKY. Ive had 3 of these trucks since then(2 currently) and Ive replaced brake lines on all of them. It was on the second one that I found the valve. Im replacing the brake cables on my current one now and it jogged my memory. With age comes wisdom
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