Brake adjustable proportional valve

Posted by Remarkable-Divide-57@reddit | projectcar | View on Reddit | 23 comments

Anyone running an adjustable brake proportioning valve on a ’75 wagon?

Post Body:

Hey everyone,

I’m working on dialing in the brakes on my 1975 wagon and looking into adding an adjustable brake proportioning valve (like the Summit one pictured).

Has anyone here installed or used one on a similar setup?

•   Did it help balance front/rear braking?

•   Where did you mount it (engine bay vs frame rail)?

•   Any issues with rear wheel lockup or dialing it in?

I’m currently dealing with the rears wanting to lock up, so trying to get this sorted the right way the first time. Appreciate any real-world advice or setups you’ve used.

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Remarkable-Divide-57@reddit (OP)

I was going to run proportional valve for just the rears. I took it to a mechanic who said everything was good. But kept locking up shortly afterwards. I was thinking a clog in the rear distribution block

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Gubbtratt1@reddit

More likely a mechanical issue than hydraulic. Either way, a proportioning valve isn't the solution. Could be seized brake components, warped drum or an oil leak into one of the drums.

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smthngeneric@reddit

Well first off what makes you think you need one? What is a "75 wagon"? Lots of manufacturers made multiple wagons in 1975. Have you changed anything in the brake system that would change the balance at all? Just want to make sure you don't actually have a totally unrelated issue going on that this won't solve. If you're positive everything is working as it should and it somehow still is locking up the rear then yes this will fix that but make sure that's actually the problem first and you'll have to either remove or gut your current Proportioning valve.

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Remarkable-Divide-57@reddit (OP)

I already replaced front lines of brakes. Master cylinder is new. All brake hardware checked good. Stopped skidding for a bit after replacing master cylinder than started again. Started skidding drinker side rear. Only when braking harder.

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MeNameIsDerp@reddit

Drinker side lol, idk if that’s on purpose but it’s amazing

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poorboychevelle@reddit

Along with everything else, did you get the correct master cylinder? The disc-drum ones are a little different than the disc-disc ones, etc

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fLeXaN_tExAn@reddit

It's a drum rear brake, right? My money is on the self-adjusters need to be cleaned out or replaced. If the rear brakes are not applying equal stopping force, an adjustable proportioning valve isn't going to help you. That just adjusts from front to back. You need back side to side.

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SupermarketFunny1813@reddit

I’ve seen out of round drums causing the brakes to lock up too.

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deekster_caddy@reddit

Sounds like you've got a problem in your rear brakes to figure out first. Adding a proportioning valve is for balancing out a working system, not a band-aid.

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smthngeneric@reddit

So only 1 side is locking up. So something isn't working correctly and this probably won't fix the issue id say either there's a clog in the rear lines or a wheel cylinder seizing or something like that.

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Kitchen-Ear1578@reddit

This is off topic, but I got that same Summit mailer recently. I was looking at the cover thinking how corny the picture is. What respectable car guy would pose and sit on the fenders, practically in the engine bay? Why not just have the dudes stand next to the car leaning into the engine bay??

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Holiday-Witness-4180@reddit

Not sure about posing for pictures, but that’s definitely where you would have people sitting while you crawl under the car with a torch to heat up the coil springs.

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trashlordcommander@reddit

I did something a bit unconventional and put it where I can adjust it inside. Only because I was trying to pull some extra time out at autoX and adjust per run based on how the car was acting

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Foreign-Commission@reddit

Does thecwqgon still gave the factory proportioning valve?

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Remarkable-Divide-57@reddit (OP)

Yes it does

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jedigreg1984@reddit

+2 on this, didn't realize you still had your combo valve in. If you have stock brakes and tire size it's pretty much all you need, as long as it's working

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Foreign-Commission@reddit

You would need to eliminate it if you plan to install a new adjustable one. Or have you tried to just replace the factory one? It may be failed

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pistonsoffury@reddit

Install it in the cabin under the dash for on-demand full front bias (to aid with... activities).

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Remarkable-Divide-57@reddit (OP)

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switchsixtwofive@reddit

I used one when upgrading my foxbody to cobra disk brakes on all four corners.

I mounted mine in the engine bay. No issues dialing it in as it’s pretty easy.

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70camaro@reddit

I added one after upgrading the drums to discs on my 70 Camaro. I mounted it so it's on the floorboard near the drivers side seat so I could fine tune it, but in hindsight it probably wasn't necessary...I should have just put it on the firewall.

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jedigreg1984@reddit

these help balance immensely, and are pretty much necessary for safety + making sure you can use your maximum braking power and modulate your brakes effectively
mount in engine bay on inner fender or similar, below level of master cylinder outputs
usually no issues getting it dialed in for the roads where you usually drive, unless you have a drag car with extremely mismatched front/rear tire tread width (even then, you just dial in more rear bias and test it until it's good). You can adjust for other conditions (dirt, track use, etc.) if you really want to. Plenty of articles and info on the internet about how these function and what to aim for.

Guys that say their hot rod doesn't need one of these are just begging to spin their car into a telephone pole

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glorybutt@reddit

Did a proportional valve on my s10. You can see it on the right fender. I basically feed it direct from the master. It does help if you lock up too much on the rear. In my case, I switched the rear axle out and upgraded to disk brakes.