# Brake Proportioning valve?? Do I need it??



## jnesbitt (Dec 24, 2009)

I have an 83 rabbit. 1.6 turbo diesel.I had to cut the lines from my master cylinder that were rusted on. The master has 6 ports, Still dont know why it has 6 ports if you only use 4 ports, the other two ports on mine are plugged.The porportioning valve was froze up and the bolt holding it on was rusted up, had to heat it to remove it, which pretty much wiped out the valve and the wire and plug that went into it. I can't seem to find a replacement. The valve only goes to the rear drum brakes. This is my second VW and my first an 80 Diesel caddy only had a 4 port Master with 4 lines each going to a brake. Why the change, I spoken to several friends that seem to think I can by pass the valve all together as non of thier rabbits have them 80-81-82. Or put an older 4 port master on and go with that..any thoughts?? I know the need for the valve or the basic concept..but seems to me it an over kill with cars that dont have antil lock brakes.


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## spitpilot (Feb 14, 2000)

*Re: Brake Proportioning valve?? Do I need it?? (jnesbitt)*



jnesbit I know the need for the valve or the basic concept..but seems to me it an over kill with cars that dont have antil lock brakes. [IMG said:


> http://www.vwvortex.com/vwbb/confused.gif[/IMG]


 Its not over kill on cars that don't have anti lock brakes...its a "poor man's anti lock brake system!...Cars become unstable..ie spin out and go down the road bass ackwards if the rear wheels lock up B4 the fronts under heavy braking.....so the concept is to reduce the hydraulic pressure to the rear brakes when car is lightly loaded..since there is little weight in rear compared to front with no load in the car...rear end rises and actuates the prop valve to cut pressure to rears....that will help prevent them from lockin up first and spinning you out. With antilock brake system..full on four wheel system....all wheels are prevented from locking up by the ABS...so no need for a prop valve at all. Know that if you leave it out, your car will be more prone to spin outs...in the rain etc..if you're a seasoned driver that knows how to correct a spin..no probs..but if you let others drive...could be an issue 4U!...Obviously drivers learned how to drive without prop valves in the "ol daze"..its just that not many do now..that's why all cars must have ABS and now stability controls mandated..drivers just don't know crap about vehicle dynamics anymore.







So the Feds are protecting us from ourselves..or at least the "clueless" drivers among us.


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## jb86 (Sep 16, 2009)

the caddy had a proportioning valve i believe mounted w/a strap to the rear axle. so not the same as your rabbit


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## o2bad455 (Aug 22, 2003)

*Re: Brake Proportioning valve?? Do I need it?? (spitpilot)*


_Quote, originally posted by *spitpilot* »_ Its not over kill on cars that don't have anti lock brakes...

Agree, it's absolutely necessary. If you can't source a stock one, there are adjustable proportioning valves available from many race suppliers. 

_Quote, originally posted by *spitpilot* »_its a "poor man's anti lock brake system!.

Disagree, a proportioning valve is much better than ABS! My old 95 GTI VR6 had a prop valve plus ABS, and braked like a dream even when the ABS malfunctioned (blown fuse). 
My newer 97 GTI VR6 only has ABS since some bean-counter must have decided it didn't need the prop valve since the ABS could compensate instead. In addition to much faster rear brake wear, the danger of this setup reared it's ugly head when one of the rear ABS sensors failed, unexpectedly sending me backwards into the guardrail when I braked hard for a dog that darted into the highway. The rear wheel with the bad sensor locked up easily without the benefit of the problematic ABS *BECAUSE* there was no rear brake proportioning valve. Genius! So, a rear brake proportioning valve is NOT a poor man's ABS, rather an ABS system is a poor man's rear brake proportioning valve! I have since added a proportioning valve to my 97 (as cheap insurance on my body repair$, if nothing else).


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## mrjoshm (Jul 24, 2003)

you absolutely need a prop valve.. i ran my jetta (which has the prop valve incorporated into the rear beam) for a week with it adjusted incorrectly and it seriously wanted to swap ends..


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## veector (Mar 1, 2006)

*Re: (mrjoshm)*

not necessary depending on what driving you do... I had my prop valvego and just ran new lines past it. This was on an 83 jetta mostly stock with a 1.6. Never really had an issue the rears would lock up first but still braked fine... it all depends how you drive. That being said I would not run without a prop valve on my heavier mk3 jetta


_Modified by veector at 5:07 PM 1-5-2010_


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## jnesbitt (Dec 24, 2009)

*Re: Brake Proportioning valve?? Do I need it?? (jnesbitt) UPDATE!!*

Ok so I pulled it..and you soo need it if you have brake assisted servo..they lock up like a champ. I pulled the vacuum off to have standard brakes no assist and they still lock up but not as bad..harder to brake this way as the pedal is very hard to push down thus the brake assit..







but all in all you still need it. My valve was ok and still works so I'm putting it back on..thanks for all the posts...


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