brake pressure regulator

[Boydskyking]

what is brake press regulator and how is it adjusted. What are the steps if you can not fine one to replace the one on my car,can you just hook it straight , go around it. Also I am rebuilding the engine 2.0 with stock P@C etc, I has 40 webers and the fuel injection has been removed. I understand that to get the goods out of the engine I need to change the cam to match the carbs. Any sugestions

[Emo993]

Are you talking about the rear brake proportioning valve.....I took mine off 30 years ago, works great. You replace it with a "T" (vw Beetle). It is on the engine lower position fire wall just after tunnel brake line comes out. Mark

[beatnavy]

I think it technically is a pressure regulator. It simply acts as a bypass until the pressure gets high enough (525 psi according to Mr. Shea) and then prevents fluid going to rears temporarily. It's designed to keep the car from spinning on hard braking, and it's probably a good idea to keep it there. I don't think the stock one is adjustable, and the adjustable ones aren't really supposed to be for street use, right?

Eric Shea at PMB Performance offers a rebuilding service on these, I think. He also sells are rebuild kit: PMB - DIY Caliper Parts

[porschetub]

Originally Posted by Boydskyking

what is brake press regulator and how is it adjusted. What are the steps if you can not fine one to replace the one on my car,can you just hook it straight , go around it. Also I am rebuilding the engine 2.0 with stock P@C etc, I has 40 webers and the fuel injection has been removed. I understand that to get the goods out of the engine I need to change the cam to match the carbs. Any sugestions

Keep the regulator where it is ,its there for a reason why would you want to adjust it?,porsche don't put parts in there cars that don't need to be there.
You can spend the time tuning your carbs to the best running condition or split your case and install a suitable carb cam but that's $$$$$,cheers

[Emo993]

I stand corrected, proportioning valve....old termanology. And Eric is the expert on brakes, thanks for all the information in the past. Mark

[Cairo94507]

I sent my proportioning valve to Eric for a rebuild/refurbishing. All of my brake components have come from Eric.

Our cars don't have any computer assisted safety technology (why I love them) so the brakes are a really big safety item. If not working properly, you really are at a significant disadvantage.

[John Rogers]

Generally what happens is air or moisture gets into the brake lines or calipers and somehow finds its way into the prop valve. Air or moisture is very hard to get rid of, even with a pressure bleeder and the result is a spongy pedal or excessive pedal travel. Even if the prop valve is okay the pedal feel is different than on modern cars with ABS or vacuum assisted brakes so many drivers replace the prop valve with the VW tee and get a very solid pedal. BUT that means there is more pressure to the rear calipers so the car can easily have the rear wheels break loose. This can be terrible, especially if the driver panics and hits the brakes in a curve and the car swings around. There have been instances of crashes and even deaths with cars having a tee and the driver caused the rear to come around.

The original intent was to make the 914 brake in a straight line with all 4 wheels having the same force. There is a slight rear weight balance and that shifts forward because of the engine weight shift and heavy braking. One place to really observe this is to watch stock 914's at an auto cross and see what happens to the inside rear wheel or both rear wheels when brakes are applied.

If you decide to put in a tee, do some practice with it since the car will be a different animal than it was before!

[larrym]

Originally Posted by porschetub

Keep the regulator where it is ,its there for a reason

agreed - the problem you will have if you totally remove it is that the rears can lock up too soon

- this can result in a 360 loop on a wet road curve

- this happened to a fellow i know - luckily he did not go over the cliff at that curve

- he put the oem valve back in

if you never brake hard on wet roads you might get away with the T solution

adjustable valves were the hot ticket for the bmw front brake upgrade - but the kits all said to put 'em in place of the oem valve - which meant you had to test-drive, check lockup, jack up car & tweak adj, the test-drive again etc etc etc untill you got it about right

i put mine in the cockpit where i can tweak it - useful for the track - it takes extra plumbing - (all of which is using old vw bubble-flare pieces)

read yesterday's post here on "m-caliper" vs bmw option

Modified m-calipers on stock 914 rotors anyone?
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