# What is the purpose of the brake pessure regulator (Golf Mk2) ?



## orwikcons (Mar 6, 2007)

What is it doing, and why is the mechanism with the spring for?


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## germancarnut51 (Mar 23, 2008)

The pressure regulator/proportioning valve controls the amount of brake fluid that's allowed to flow to the rear brake calipers or drum brakes to control the amount of braking force generated in the rear of the car.

The harder you stop, the more the nose of the car dives, and as the nose of the car dives, weight is transferred from the rear wheels to the front wheels. This makes it possible to put more brake force on the front wheels without the wheels locking up and skidding. At the same time, as less weight is on the rear wheels, it becomes easier to lock up the rear brakes, causing a skid. The proportioning valve limits the amount of brake fluid flowing to the rear brakes as the rear of the car rises (and the front of the car dives) the spring attached to the axle beam is pulled, working on the lever, and limiting brake fluid flow to the rear brakes.


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## orwikcons (Mar 6, 2007)

Thank you for nice explanation


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## BiH (Nov 27, 2000)

you have to adjust it when lowering the car and also when bleeding the rear calipers or drums rear wheels have to be on the ground so it opens the valve.


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## spitpilot (Feb 14, 2000)

This is the "poor man's ABS"....tries to keep rear wheels from locking up during hard braking so you don't spin out...ABS does the same thing but much more effectively! In fact it appears that since goin all ABS..VW has increased the brake bias on the rear axle, since rear pads seem to wear much faster now than in the preABS daze.


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## GTI Jay (Feb 11, 2010)

i noticed that i have this on my mk3 GTI VR6 and just yesterday i had to slam the brakes and i did infact spin out quite badly. no collision. VERY close though. stupid ********** cant see me coming down the highway  When i finally stopped i was sideways pointing at the median about 50 feet from the intersection in the rural highway. pretty much as soon as i hit the brakes hard i started to go sideways is this bacause of this brake pressure thing?


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## germancarnut51 (Mar 23, 2008)

I'm not a expert on VR6s, but didn't some come with ABS, and some came with the brake proportioning valve? If your car has the proportioning valve, and not ABS, it's more important than if you had ABS to be careful when changing springs or to coilovers because you are changing the ride height of the car, and the brake proportioning valve will not be optimized to work at the new ride height (unless you play with the adjustment, and test before you have to make a panic stop).


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## GTI Jay (Feb 11, 2010)

I understand what you are saying germancarnut, but my car is all stock springs struts and shocks. Nothing is modified with my suspension its all stock. My car was equipped with ABS I know this because I have the ABS control module under the rear seat and the ABS speed sensor rings on both the front wheel hubs. (which I accidentally destroyed while changing cv axles in the summer) so I know my ABS is eternally f****** lol but what I am saying is that my '95 GTI VR6 was originially equipped with BOTH brake proportioning valve and ABS. I know this because I can see the valve and spring thingy mounted to the rear axle beam with 2 brake lines in and 2 out.


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