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Old 07-02-2019, 12:01 PM   #1
WyattTX
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Location of brake Proportion valve: Does it matter?

I notice many aftermarket master cylinders have the P valve directly under the master cylinder. But most OE P valves are long distance away from the master cylinder (like near the front bumper, or the center of the frame). Why is this? Is there a benefit of the P valve being further from the master cylinder, or are manufacturers just being mean and making it difficult to reach for nothing?
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Old 07-02-2019, 01:22 PM   #2
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Re: Location of brake Proportion valve: Does it matter?

my mid 80's truck i swapped to disc / disc and used a adjustable rear bias aftermarket valve and its next to the master now since i replumbed the hard lines and no problems.
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Old 07-02-2019, 01:23 PM   #3
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Re: Location of brake Proportion valve: Does it matter?

The "valve" on these old trucks is merely a junction block and not a proportioning valve. Not sure if the block needs to be so close to the master cylinder. But a proportioning valve can be anywhere as long as it can control the amount of fluid to proportion the front and rear brakes accordingly.

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Old 07-02-2019, 02:30 PM   #4
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Re: Location of brake Proportion valve: Does it matter?

Interesting. I just remember replacing a P valve on an 82 Jeep CJ8 (front disc, rear drum). It was bolted in the worst possible place, IMO. It was inside the C channel frame under the vehicle. I figured AMC engineers put it there for a reason, but maybe they were just jerks, afterall.
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Old 07-02-2019, 03:35 PM   #5
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Re: Location of brake Proportion valve: Does it matter?

.I've gottem mounted on front crossmember and at mc on different trucks...all it is is a junction/dividing point...doesn't matter where it is...I prefer it down low just from a visual standpoint...
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Old 07-03-2019, 07:33 PM   #6
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Re: Location of brake Proportion valve: Does it matter?

No if it's bled properly it is a hydraulic connection, so no problem with the distance.
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Old 07-12-2019, 10:33 AM   #7
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Re: Location of brake Proportion valve: Does it matter?

GM ran the single front line feeding the valve as far as possible before splitting for each front line. Least amount of tube = lowest cost. Uses the prop valve as a L/R front line splitter too, thus saving another T. Plus it allowed the same location for all the brake combinations including the hydroboost mess, which doesn't play well with prop valve on MC.
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Old 07-14-2019, 06:46 AM   #8
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Re: Location of brake Proportion valve: Does it matter?

Ah, so the bad location is just cost cutting. That makes sense. Thanks for the info, everyone.
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Old 07-14-2019, 07:01 PM   #9
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Re: Location of brake Proportion valve: Does it matter?

Had a 79 Camaro with the P-valve bolted to the MC-Booster assembly.
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Old 07-14-2019, 07:36 PM   #10
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Re: Location of brake Proportion valve: Does it matter?

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...Plus it allowed the same location for all the brake combinations including the hydroboost mess, which doesn't play well with prop valve on MC.
I assume you mean the physical interaction between the steering hoses and the P-valve? -- two objects trying to occupy the same space?

Or is there something else that I'm not getting here?
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