Removing Rear Compensators From A 1.9

[Tom Fenton 1,541]

No. To reduce force exerted by the rear caliper you need to reduce the pressure at the caliper. System pressure is governed by the mechanical effort exerted on the master cylinder by the drivers foot via the pedal ratio.

To REDUCE the effort at the caliper you need to INCREASE the pressure drop over the bias valve. To INCREASE the pressure drop over the bias valve you need to CLOSE the valve to restrict the flow and therefore induce a pressure drop across the valve itself. This pressure drop is taken away from the initial system pressure from the master cylinder and therefore you get a REDUCED pressure at the caliper.

[Rob Thomson 6]

Ehh?

 

Regardless of how the compensators work, when they're in their 'open' position they allow the full pressure generated by the MC to operate the rear brakes. As they're closed that pressure is reduced. Simple.

 

I had a (cheap and cheerful) Tiilton bias valve fitted to my trusty old 309 GTI with standard brakes. I only ever used it in its fully 'open' position (maximum rear braking). The balance was perfect, rears locking more or less with the fronts which is how I like it. Move the lever towards the 'closed' position and the rears did less and life was dull.

 

I had a (decent) AP bias valve fitted to my 106 Rallye stage car. In it's 'open' position the rears locked WAAAY before the fronts. Indeed, it needed 'closing' almost all the way to get the balance back where I liked it, i.e. the rears locking with the fronts.

 

I'd be really surprised if a 205 with uprated front brakes needs any form of limiting valve, but a bias valve should do the job without any probs. Just get a decent one.

Edited April 15, 2008 by Rob Thomson

[jonnie205 1]

This suprises me, the bias valves even have written on to wind outwards to increse force to rear etc. It also works i have just been out in my 206 rally car and when you unwind - make hole bigger it definately stops rears locking and then when i wind it in to reduce hole size it increses presssure and locks rears. Oh well ime not 100% on the physics but winding it ourtwards has always reduced prressure to rear in cars i have driven. It like on gravel we have a setting of

Gravel - where you want the rears to do more work, left foot braking etc

Wind valve fully in then wind out 2.5 turns

 

tarmac - Need virtually all effort on front

Wind fully in then wind out 4 turns

 

Oh well i probably wrong

Edited April 15, 2008 by jonnie205

[welshpug 1,657]

Gravel - where you want the rears to do more work, left foot braking etc

Wind valve fully in then wind out 2.5 turns

 

tarmac - Need virtually all effort on front

Wind fully in then wind out 4 turns

 

if you do indeed set the valve as you say you'll have more braking effort at the rear on your tarmac setting, front pressure will be unaffected.

[jonnie205 1]

yes front should remain the same, just looking at it i think its a weird type valve in my 206, the adjuster is not directly related to the hole opening size

[base-1 17]

Guys you're talking slightly across purposes and are both right Bias valves aren't just a through pipe that you restrict or allow to be open/normal depending where the lever/screwknob is set. There's a piston arrangement inside and what you adjust with the knob by screwing in is the pressure at which it operates, and changes the pressure ratio between inlet and outlet.

[James_R 3]

Regardless of how they work, I found 6 brakes with no comps and 23mm MC work fine. I run std 1.9 calipers and discs front and back and foudn swapping comps to a wilwood tilton stlye one and increasing the rear effort helped stablise the car, and I can add more braking to the rear in the wet to help things more.

 

As tom said his runs GTi180/407HDI size pistons, and has little rear effort

 

not kean on 1.9 comps myself seem to play silly buggers :S

[C_W 3 1 Cars]

Are we getting valves plumbed so that they are connected front vs rear mixed up with variable adjustment just to the rear brakes? or does that not make any sense

[Anthony 1,003]

Are we getting valves plumbed so that they are connected front vs rear mixed up with variable adjustment just to the rear brakes? or does that not make any sense

To run a bias valve you need to run a single brakeline to the rear and have a front-rear split - like 1.6's are as standard.

[Spiky 37]

i run gti6 calipers up fron with ds3000 pads and std calipers with ds3000 on the rear

 

on eagle f1's and r888's

 

my rears NEVER lock before the fronts

 

the disc wear on the back is normal so for me it's fine (running no compensators)

[Wurzel 16]

I didn't think the bias valve worked in the method of increasing a hole size?

 

I always understood them as being a valve that pressure from the master cylinder needed to overcome before allowing a flow through. The more you wound down the knob, the greater the spring pressure on the valve and therefore the more pressure req'd before a flow.

 

Anyways, I had the GTi -6 set up with 1144 pads front and rear. Car was awful under heavy braking with the rear squirming all over the place. Removed compensators and the balance was restored measurably. I felt a lot more confident in the car, rear didn't lock up in wet or dry conditions and MOT's passed every time. I felt that using the larger brakes up front required slightly more braking effort from the rears to compensate. An old argument that I think will never really be resolved on this forum. It worked for me though.

 

It's not too much effort to try without the compensators, a small bypass pipe could be inserted (how I did it). Try it and see.

[nick 3]

Never quite understood the "big brake/no compensators" thing?? If you can lock the wheels with std 1.9 brakes and you can lock them with gti-6 brakes the limit is tyre grip. I can't see how gti-6 brakes can take more weight off the back end (so as to not need compensators) as far as i see it you are just getting to the same end in a different way, getting to the point of maximum adhesion (and beyond) with both, but using less effort with the "6" brakes??

 

Nick

 

Hope that makes sense...

[tenchu 1]

Has anyone ever managed to refurb a 1.9 compensator?

 

Had to whip mine off to get through the last MOT, but don't really fancy paying £40+ for a new one.

 

Finding it nigh-on impossible to crack the bloody thing open, is it even worth the bother?

[C_W 3 1 Cars]

Never quite understood the "big brake/no compensators" thing?? If you can lock the wheels with std 1.9 brakes and you can lock them with gti-6 brakes the limit is tyre grip. I can't see how gti-6 brakes can take more weight off the back end (so as to not need compensators) as far as i see it you are just getting to the same end in a different way, getting to the point of maximum adhesion (and beyond) with both, but using less effort with the "6" brakes??

 

Nick

 

Hope that makes sense...

 

I see your arguement but if you were to retain the same "balance" (locking aside) then you would think that, with a big brake upgrade up front, removing the rear compensators would restore the braking balance?

[saveloy 8]

Chris, I have, as you probably know, Hi-Spec 4 pots up front and std rears. I use an AP bias valve plumbed into the rears only, and this is set to fully open. And I have no compensators.

I have had no issues whatsoever, on road or track. And this is the set up I would wholly recommend.

You would, perhaps, given the size of your front set up, need to close up the bias valve a bit though.

Edited May 7, 2008 by saveloy

[fangio 1]

I think you all might find this enlightening. Click

 

I hacksawed through a non-working compensator a couple of years back and couldn't suss how it worked until I read the above.

 

As the article warns those that have chosen not to have compensators fitted may not ever experience a problem - but then again you might.

 

For me having read the article and I hope understood correctly, ultimately there is only one safe option.

[DamirGTI 342]

Fit 1.6 system from my experience 1.6 system is better/simpler then 1.9 , you'll need just one compensator (but it must be fitted on to the chassis rail at specific angle and turned to the right direction) T splitter for the rear brake pipes , and one brake pipe which goes from the RH rear wheel to the T splitter .. connect everything up , plug off one master cylinder outlet ditch long brake pipe on the right side and bob's your uncle

 

1.6

http://www.stuartmcguire.co.uk/pug/GB/205F/4/48A40A.HTM

 

1.9

http://www.stuartmcguire.co.uk/pug/GB/205F/4/48A60A.HTM

 

Rgs !

Damir

Edited May 9, 2008 by DamirGTI