Removing Rear Compensators From A 1.9

[C_W 3 1 Cars]

I've had problems with the compensators in the past and remember them being £40 or something each. At the MOT the guy said the rear brakes aren't doing much and under hard braking my car is pulling to the left and I suspect it's these playing up again. All discs and pads are fine and all calipers are free. My car has a big brake upgrade on the front so with that in mind I think removing the rear compensators completely should be ok?

[davemar 16]

At the MOT did you note down the reading of the front brakes? You still want your rears a lot weaker than the fronts, but if your big-brake fronts are a lot stronger than the standard, then you might be OK removing the rear compensators.

 

I had problems at my MOT over the rears. I had a compensator going 'open circuit', so one of my rears was reading a lot higher than it should be. The MOT guy assumed that the high reading was normal and the weaker rear brake was the problem one. When I replaced the dodgy compensator with a new one, both rears were the same and quite weak (which as others on here have suggested is normal). The MOT guy thought they were too weak (though he did pass them in the end with a bit of jiggery-pokery), though they were with 5% of each other and the overall braking was well above the minimum required.

 

With the 'open-circuit' compensator I think the brake was pulling about three times the force than it was with the new compensator. I doubt your fronts are 3 times as powerful as standard, so you still might want to keep some sort of compensation on the rears, but maybe using a different method?

[C_W 3 1 Cars]

At the MOT did you note down the reading of the front brakes?

 

There wasn't much reading from either, but the handbrake worked fine so we guess it was a fluid problem/blockage. I removed the rear pads and could pump the piston pumped out of either side as normal, and when bleeding the brakes thefluid came out ok too but they just weren't very strong.

[jonnie205 1]

dont remove them , the rears will lock up especially on track. I just ftted some back to a track car where they had previously been taken off and now much better

[C_W 3 1 Cars]

OK, thanks for that, I'll work out which one is dodgy (I remember last time it was difficult as davemar said sometimes the faulty one is the one that is braking "better").

[Baz 421]

Yes it'll be fine if you have larger brakes up front.

[Tom Fenton 1,525]

I don't agree, if you use your brakes hard on track or even on the road with no compensators in then the back wheels can lock up under heavy braking, which is generally when you least want to be having to control a huge sideways moment.

 

If you really want to get rid of them my advice is to re plumb the rear brakes and use a single inline adjustable bias valve to set them up and regulate rear braking.

 

This is from personal experience on my track car, this now has a bias pedal box with twin master cylinders instead.

Edited April 14, 2008 by Tom Fenton

[Baz 421]

With std front brakes yes, i learnt that the hard/fun way... But with uprated fronts as i say there's no reason why it shouldn't be fine, I know Anthony used to run 6 brakes up front with no compensators.

[Peetypug 5]

i've been told i can run my road car with no compensators, but i will be having gti6 fronts

Edited April 14, 2008 by sorrentopete

[Stu 18]

Ive not experienced any problems with my setup, no locking up under heavy braking anyhow (and ive had a few moments.. )

 

Ive got '6 front setup, with 406 M/C, and stock rear 1900 brakes with the comps removed.

 

I had the same thing last mot time, except i needed to do both front-rear brake pipes at the same time so it made sense to do away with the compensators when i made the new lines up.

Edited April 14, 2008 by stu da rude

[eafertynyne 1]

I've got a 307HDI front set-up with 406 MC and my std rear 1.9's were still locking up prematurely.

 

The compensators have now been refitted and the brakes work perfectly.

 

My advice...Don't remove them!!

[Guest MattyC]

i believe you need some thing in there as well, instead of the stupid price for new ones, a rally type in line brake bias valve is cheaper and lets you set it up how you like.

[Anthony 1,000]

I ran GTi-6 front brakes and standard 1.9 rears with no compensators for about 10k miles, and never had any problems at all - the car saw about every different situation possible as well - wet and dry trackdays, road use in sun, rain, snow, and ice.... and never had any issue with the rears locking prematurely.

 

Not entirely sure how well it would work if you've got 1.9 calipers and 285mm disks though - the other option you've got is to retrofit either a bias-valve or 1.6 style compensator, both of which should be just fine and the 1.6 compensators don't have the reliability issues of the 1.9 ones.

[Alastairh 47]

I run 6 brakes and no compensators and thats fine.

 

Also previously built a 205 with S16 calipers up front, 1.9 mc, 1.9 rear brakes and no compensators and stopped very well.

 

Al

[tom_m 0]

i run 206gti 180 fronts with a 22mm mc and no compensators, the fronts lock waaaaaay before teh rears!

 

i put a bias valve in to be on the safe side and its set all the way open, readings on the mot were normal like this.

[jonnie205 1]

bias valves dont work well on 205s

 

A bias valve in its least braking effort to rear is a large open hole trhough bias valve equivalent to not having valve at all. Basically having a bias valve on its least pressure setting is like having no compensators which we have found out locks rear wheels. A bias valve will only the adjust to give more pressure to rear.

Compensators must do something about limiting the quantity of fluid rather than just the pressure or somethin.

[Emmy Seize 8]

I share Tom Fenton's view on the issue.

 

Single line, bias valve - problem solved!

 

I run a 6 setup with front/rear split and a 23,8mm bore master cylinder.

 

If you set the bias valve to fully open, the rear wheels tend to lock up.

 

The valve on my car has been set up on a MOT testing bay to figure out what was best.

 

The braking force was tuned down to roughly two thirds of the effort originally measured with the valve fully open.

 

I had no scary sideways-under-braking moments ever since.

[C_W 3 1 Cars]

Not entirely sure how well it would work if you've got 1.9 calipers and 285mm disks though - the other option you've got is to retrofit either a bias-valve or 1.6 style compensator, both of which should be just fine and the 1.6 compensators don't have the reliability issues of the 1.9 ones.

 

How are 1.6 ones fitted? can you fit two of them? are they load-sensitive?

 

I thought about the standard calipers could cause a problem, although the brakes in generally are pretty crap at the moment to be honest, they just feel very wooden - I'm not sure if I'm used to the BMW now (but then again I drive other cars that I used to think didn't have as good brakes as the 205 and they still feel much better).

[C_W 3 1 Cars]

I don't agree, if you use your brakes hard on track or even on the road with no compensators in then the back wheels can lock up under heavy braking, which is generally when you least want to be having to control a huge sideways moment.

 

If you really want to get rid of them my advice is to re plumb the rear brakes and use a single inline adjustable bias valve to set them up and regulate rear braking.

 

Where would I get one of these? and do I need two, one for each rear brake line or have you plumbed the brake lines to feed both rear calipers?

 

Or does any have any known good compensators?

[Baz 421]

Just a normal adjustable bias valve, use a single line to the valve, then split to each rear brake. Like Adam's here.

http://img.photobucket.com/albums/v418/205...ma/Image011.jpg

 

 

Yes i have a pair of good compensators from my Goodwood.

Edited April 15, 2008 by Baz

[jonnie205 1]

If you are locking rear wheels with no compensators a bias valve will not resolve the problem. The bias valve full open (large hole) is low pressure to rear brakes, least likely to lock. A bias valve fully open is same as having no compenstors and no valve. As soon as the valve is screwed in the hole gets smaller and more pressure is sent to rear brakes.

[jonnie205 1]

emmy you are wrong. A fully open valve increses the hole size and lowers pressure. As you screw valve in the pressure will increase as size of hole reduces

[Tom Fenton 1,525]

If you are locking rear wheels with no compensators a bias valve will not resolve the problem. The bias valve full open (large hole) is low pressure to rear brakes, least likely to lock. A bias valve fully open is same as having no compenstors and no valve. As soon as the valve is screwed in the hole gets smaller and more pressure is sent to rear brakes.

 

You are getting flow and pressure mixed up here. Flow makes the caliper piston move, pressure exerts a force on it. Moving the piston does not give braking effort, exerting a force on it does however.

 

With a bias valve fully open you have full pressure which is generated at the master cylinder applied to the rear brake caliper piston. Flow is irrelevant, as once you have taken up any distance between the pads and disc caused by pad knock off or the seals in the calipers pulling the piston back slightly, pressure is the only governing unit causing any more or less axial load on the brake pads and hence braking effort.

 

With the bias valve closed down, you limit the amount of pressure available at the brake caliper by inducing a pressure drop across the bias valve as it restricts the line. Thus you have less pressure at the brake caliper, (Full Master Cylinder Pressure (minus) Pressure drop across the bias valve = Pressure at caliper) therefore less axial force, therefore less braking effort. (Force=Pressure x Area; the area is the area of the brake caliper piston, thus this is constant in this example).

[Tom Fenton 1,525]

emmy you are wrong. A fully open valve increses the hole size and lowers pressure. As you screw valve in the pressure will increase as size of hole reduces

 

A fully open valve increases the hole size - YES.

 

A fully open valve increases the hole size and lowers pressure - ON THE PRESSURE GENERATING SIDE OF THE VALVE, YES, SO IN THIS CASE ON THE MASTER CYL SIDE OF THE VALVE

 

A fully open valve increases the hole size and lowers pressure - ON THE DELIVERY SIDE OF THE VALVE, NO, SO IN THIS CASE ON THE CALIPER SIDE OF THE VALVE.

 

 

As you screw valve in the pressure will increase - ON THE PRESSURE GENERATING SIDE OF THE VALVE, YES.

 

As you screw valve in the pressure will increase - ON THE DELIVERY SIDE OF THE VALVE (I.E. CALIPER) NO.

 

As you screw valve in the.... hole reduces - CORRECT.

[jonnie205 1]

yes, so to reduce force exerted by rear calliper you wind open the valve to create a larger hole? on all valves i have ever used on rally cars etc its always a case of opening valve to reduce braking force to rear of car is that how you see it?