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bobbber · Posted: Mon Jan 19, 2004 11:13 am Post subject: Rear brake compensation valve

Guys,

My 33 has one of these and it is failing to function properly. I understand it uses the level at the back of the car to adjust the braking on the rear... reducing the rear breaking as the back of the car lifts. The left wheel brakes fully no matter what the level is.

What are the arguments against fitting a bracket to the piston, so the braking 'power' to both rear wheels is constantly enabled (i.e. making the valve pushed in permanently)?!?!?!?

Lots of cars do not have this valve - so why does my 33 need one?!?!

Thanks!

Rob
_________________
Fiat Bravo 165 Sport

Marcin · Posted: Mon Jan 19, 2004 12:20 pm Post subject:

Hi,

if there's too much braking force going to your rear wheels you may unintentionally end up in a uncontrollable spin, just as you were using your hand brake in a hand-brake turn. This may bring you in an awkward situation on the road.

Marcin

Eddie W · Posted: Mon Jan 19, 2004 9:33 pm Post subject:

Hi Rob
Wouldn't like to press on really hard without it. Even with mine working I've managed to lock the inside rear when taking a long blind corner to find I was doing about 3 times the speed of some motorbikes in front. Very hairy and without the bias valve, I would think pretty lethal. And that was with the s2 front suspension which pitches less under brakes.
Regards Eddie
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A LITTLE FURTHER A LITTLE FASTER

bobbber · Posted: Tue Jan 20, 2004 10:32 am Post subject:

Guess I'd better sort it out then!

Other cars don't have them though.... do you think there's something special about the Alfa which requires it?!?!?
_________________
Fiat Bravo 165 Sport

Marcin · Posted: Tue Jan 20, 2004 11:12 am Post subject:

I think that most cars DO have a braking force restriction for the rear wheels, but it's just constructed in a different way.

Marcin

Ravi - 86QV · Guest

Hi all - my brake compensation valve is not working properly either. However the problem is different - the right rear wheel always locks before the left.

Is there any way to fix and/or address this problem?

Graham · Posted: Thu Jan 22, 2004 11:17 pm Post subject:

The Rear Compensation Valves on an Alfa 33 stop working 6 months after they leave the factory. On My Car I have completely removed it and the car now is much more responsive and I have had no trouble whatsoever without it there. I had to get and inline T Piece to replace it but of course and its brilliant. Then again I do also have a modified pedal box out of a GIacatolo which has front/rear bias adjustability which I guess does its job anyhow
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5 Alfa 33's, 2 Suds God there is no help for me

Also own 2 Complete 16V Engines(Spare) And Have a Sud Rally Car in Production

Scott Sander · Posted: Fri Jan 23, 2004 12:04 pm Post subject:

Ravi,

The RPV is a non-serviceable item. If it does not work or leaks the only option is to replace it, assuming you want to keep a standard setup.

If you do replace it, you will need to adjust the new one for the correct setting. Info can be obtained in the workshop manual.
_________________
Scott Sander
'91 Alfa 33 Boxer 16V Monza - Awesome
http://www.sanderfamily.com

Sergio · Posted: Fri Jan 23, 2004 1:52 pm Post subject:

@Scott, what do you mean by adjusting the valve?
is it adjusting that little lever where the spring is set or is it on the valve itself?

I have a new valve but breaking at the rear isn't famous... so says the anual inspection...

All the best

Sérgio

gritsop · Posted: Fri Jan 23, 2004 8:31 pm Post subject:

Hi,

Installing a new valve involves the following:
After removing the old valve:

1.Not fully tighten the securing bolt of the panhard rod
2.The car should be loaded in static load (50kg in passenger comp. & 75 luggage)
3.After that, tighten the bolt of the Panhard rod.
4.The valve has a hook which should be loaded with around 8 kilos
5.Then press the piston up to the end of travel and tighten the equaliser nut

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

Scott Sander · Posted: Fri Jan 23, 2004 9:32 pm Post subject:

Sergio,

Yeah, the on car adjustment of the lever. The valve itself has no adjustment.
_________________
Scott Sander
'91 Alfa 33 Boxer 16V Monza - Awesome
http://www.sanderfamily.com

Dicko · Alfasud Joined: 17 Jan 2004 Posts: 49 Location: Sydney

Hi...

since I had new front pads put in my S1, The biasing doesnt seem to be as pleasurable.(less braking from the back).I used to enjoy the smoothness of the brakind front/back balance.

Guess it just needs adjusting. Or different grade front pads???

RIch

lesthegringo · Alfasud Joined: 23 Jul 2003 Posts: 97

I am building a rear engined 16v powered home built special, and I've stripped out a 33 16v for parts. Included in that is the compensator valve, and being in portugal, the part hasn't rusted solid. I've taken it apart to check it all out, and discovered exactly how it works.....

Its like this.... the plunger that sticks out of the bottom is not supposed to be pushed in (or up when installed), it's rest position is fully in, held against a spring.

When you hit the brake, the hydraulic pressure pushes the two inner plungers out against a disc connected to the plunger you actually see that rests on the spring bar. Depending on whether the car is loaded at the back or not, the bar will be higher or lower, and so will stop the plunger sooner or later.

Until the plunger is stopped, no pressure will be applied to the rear brakes, as the movement of the plunger is absorbing the pressure. Once the plunger stops, the pressure is then fed to the brakes. Because of the 'spring' bar that the plunger actuates against, the way that the pressure is applied is progressive rather that all or nothing.

The way to test the valve is to apply hydraulic pressure to it with the outlets blocked off - the plunger should push out without leaking around the boot.

Hope this helps save someone some cash.....