Bypassing Brake Compensator Valve (1.6 Gti)

[205_sunderland 4]

i can not find a second hand valve anywhere local and on;ly early gti's have them fitted so i was going to just bypass the vavle all together. Will doing this make the car unstable at the rear under braking or will i just have to not be as harsh on the brakes at times. I can wait any longer really as my car is sitting leaking from there and it driving me insane as i cant get one no matter how hard i try. And cash flow stops me getting a new one.

 

regards michael

[max0 5]

i can not find a second hand valve anywhere local and on;ly early gti's have them fitted so i was going to just bypass the vavle all together. Will doing this make the car unstable at the rear under braking or will i just have to not be as harsh on the brakes at times. I can wait any longer really as my car is sitting leaking from there and it driving me insane as i cant get one no matter how hard i try. And cash flow stops me getting a new one.

 

regards michael

 

Hi michael, im half way through doing my brake pipes and thought about missing it out. The haynes says it just stops the back brakes locking up. What do you guys reckon to removing it? Is it safe todo so?

 

Cheers

Andy

[Wurzel 16]

To be honest, if you're still using standard front brakes I'd leave it in the system.

 

I replaced the front brake system on my 1.9 some time ago (upgrade or downgrade is still debatable). The back end used to feel a bit vague when braking hard, some said it was due to the weight transfer but I was a little dubious about this.

 

I recently removed the rear bias valves on mine and the braking has now become a lot more balanced. It took a couple of runs on a quiet (as in dead end) road to do some braking tests and ensure the rear wasn't going to spin around. It was wet as well which helped. I couldn't get them to lock up which pleased me.

 

 

As for your set up, the only thing I will suggest is to keep it in the system. If you choose to remove it, ensure you thoroughly test it out somewhere where only you will suffer damage. Remember, dry braking is very different from braking in the wet so both needs trying first.

 

An alternative way of looking at it is the price of a new valve from a motorfactors is a lot cheaper than buying a new car

[Beastie 1]

Although they are often referred to as compensators these days that's not what they are. They are in fact limiting valves and yes, they do stop the rear brakes locking too soon. If you don't have one fitted then the driver will have to reduce pedal pressure sooner due to the rear brakes locking up and therefore stopping distance will be increased. To illustrate how important these are: Someone brought me a Bristol car which had been converted to front discs with a servo. The rear drum brakes are more energy efficient (although overall less effective) than discs due to their self - servo action which meant that the car locked its rear wheels under heavy braking. I fitted the brake limiting valve from a 1.6 gti to this car and I guess that it must have reduced it's minimum stopping distance by around 30%. Most cars use either fixed limiting valves with the exception of vans and estates which use load sensitive limiting valves. The one on the 1.6 GTI has always struck me as being a particularly elegant design for it's purpose since it is inertia sensitive: The reason that it is mounted at an angle is because it contains a shuttle valve which climbs uphill under braking. This means that as you start to apply the brakes the rears will be applied with little restriction. As the car starts to slow the shuttle valve will begin to limit the brakeline to the rears in order to stop them locking. The hydraulic requirements for rear drum brakes combined with front discs is somewhat different for a given weight distribution than the requirements for discs all round. This is why the arrangement of the 1.9 is rather different from the 1.6

[GLPoomobile 958]

So to put that into laymens terms, what does this mean for anyone who has converted to rear discs but kept the original 1.6 inertia valve?

[Beastie 1]

It probably means that you could safely use more pressure to your rear brakes and therefore gain a slight improvement in brake efficiency. Discs need higher line pressure than drums because they are not self energising.

[205_sunderland 4]

oh well looks like i going to have to keep lookin for one:(

[max0 5]

Cheers for the replys. I think ill leave mine on then

[pug_ham 245 3 Cars]

Personally I wopuldn't remove it, I'm running rear discs on mine still atm until I do the four line set up over summer & I've managed to lock my brakes quite easily on track several times last year so without it I thinking it would be dangerous on the road.

i can not find a second hand valve anywhere local and on;ly early gti's have them fitted so i was going to just bypass the vavle all together.

They are fitted to all 1.6 GTi during the run of them being made afaik, only ABS 1.6 GTi's don't have them fitted.

 

Why do you need a new one?

 

Have you priced a new one up? I don't think they are that expensive (£31.50+ vat from GSF) & its probably wiser to get a new one rather than a second hand one.

 

Graham.

[jackherer 543]

They are fitted to all 1.6 GTi during the run of them being made afaik, only ABS 1.6 GTi's don't have them fitted.

 

Ahh I didnt know that, I'm still trying to work out what to do with my mates 205 (wizeks old car). Its got wilwood 4 pots and 1.9 rear discs but it was originally a 1.6 with ABS. At the moment its got a 1.6 limiter fitted (not from the factory) but its not ideal and Im now planning on fitting a wilwood bias valve in place of it.

[pug_ham 245 3 Cars]

If you are doing away with the standard 1.6 pressure reducing valve but not swapping to a four line mc I'd definately fit a bias valve.

 

I'd like to know what way to turn the body of the standard one to change the proportion of braking to the rear.

 

Graham.

[jackherer 543]

I need to have a closer look as I'm pretty sure it has a 4 port mc (from a 406 or something, it has a modern reservoir) which must then connect to the abs block but I'm not sure if Andy plumbed the limiter before or after the abs. Am I right in thinking 205 abs has just one line to the rear?

[pug_ham 245 3 Cars]

Am I right in thinking 205 abs has just one line to the rear?

Not lookling on the parts CD here & here but they are both listed as optional ABS & the standard pages don't list any with ABS.

 

Has a two port mc & then two pipes from the ABS block to the rear brakes.

 

Graham.

[205_sunderland 4]

i need a new one because its leaking brkae fluid on the end of it.

[Beastie 1]

I'd like to know what way to turn the body of the standard one to change the proportion of braking to the rear.

 

Graham.

 

Since it operates via the shuttle valve climbing the valve body cylinder it seemed to me that the more you return the assembly to the horizontal position, the greater proportion of braking will be given to the rear. To this end I made up a mounting bracket with radially slotted holes so that I could adjust the valve. This seems to have confirmed the theory! It is a difficult change to measure because the valve is inertia operated so it's effects can't be measured on rollers. The valve also has an initial restriction which applies even when it is horizontal so the effect of altering its mounting angle are hard to measure conclusively even with a Tapley meter, except under very hard breaking.

[jackherer 543]

Not lookling on the parts CD here & here but they are both listed as optional ABS & the standard pages don't list any with ABS.

 

Has a two port mc & then two pipes from the ABS block to the rear brakes.

 

Graham.

 

having slept on it I think I was remembering that the abs apparently can't apply the rear brakes independantly of each other.

 

 

did 205 1.6 GTIs with ABS have rear drums or did they come with discs from the factory?