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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

I had my brakes checked, my pre mot test and it failed as i expected it to but on binding on the side i just put in a new rear cylinder.
I stripped both rear shoes and cleaned all contact points and shoes with sand paper and lubricated everything with copper slip. Adjusted everything up and re tested and didnt get binding this time but rear brakes were only showing 1 on the guages with the foot pedal and under 1 with hand brake.
The test results from before showed the following, but i cant make head or tail of them, what should they be? Where i had the test done they normally do trucks and lorries and my mate isnt an mot man, could he be used to lorry and truck readings and thinks mine are crap in comparison?

Admin · Posted: Tue Aug 05, 2008 6:38 pm Post subject:

Hi

If you do the fixed bits as code then it will maintain the spacing.

Not sure about the imbalance. 29% is a hell of a lot, but check the obvious like tyre pressures. I assume you have the system thoroughly bled through.

Also you mention that you did this at a truck place. Is is possible that the rollers are set up for far larger diameter truck wheels and it is somehow pinching the wheel / tyre?

All the best

Keith
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

thanks for the tip on the code, good to know, is this mentioned somewhere on this site and i didnt see it??

The place does car mot's as well and use a standard brake tester for cars. Front brakes are ok rears have 1 hand brake not good and the other foot pedal not good.
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Ben_nz · Posted: Wed Aug 06, 2008 1:13 pm Post subject:

I think the numbers those brake tests give you are a measure of how powerful your brakes are - big heavy cars with large brakes score higher numbers. Maybe your mate didn't notice how light your car was.
I always thing of those readings as being in magic brake units, because it seems that as long as the brakes are functional, the difference between readings on the same axle is the important thing. I.e. it's a bit concerning that your left front brake is apparently 29% stronger than your right front brake. That wheel might lock up prematurely and make you crash.

I failed my WOF recently because my rear brakes were out of balance, so I went out to do some panic stops in the rain and sure enough the stronger rear wheel felt to usually be locking up first, sliding the car's bum to one side.
Soon as I get a dry weekend I'll have a look. I'm not sure whether the 33's rear brake bias valve can go faulty and give more braking to one side than the other, so I'm going to stick some weight in the boot before my retest.
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

We put in the gross weight of 2525 instead of 1066, "I think" we got that number from the plate under the bonnet, but we miss read it.
Yup, whilst round Paul H's we removed the left side to check pad wear and I copper slipped up things before assembling, I shall do the same on the other side and see if that helps.
I swapped the rear axle today, with help from Paul H, "thanks Paul, V much"
I kept my new cylinder and left his other cylinder on. I used Paul’s drums and made up the best shoe pair we could, all the same make. The drums are knackered and the mechanic said I should have kept mine, we used a Dremel type of air tool to get rid of the huge lips.
Foot brake is even now but hand brake is stronger on one side, there is slack on the cable that is weaker. I might try and shim that up, I have a new handbrake cable but if I swap it, it might end up being shorter that the other side as it’s new and un stretched.
Should I try my old drums, maybe the handbrake cable nipple in the rear shoes isn’t sitting correctly?
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Admin · Posted: Thu Aug 07, 2008 11:54 am Post subject:

Hi

Have you played with the adjuster inside the drums?

All the best

Keith
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Oh yes, i figured out how it actually works form one of pauls that we made a good set. I have never had a working adjuster, now i have 2 but it probably wont work in situ. Someone had actually put one of my cogs adjusters the wrong way on.
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Well I swapped over the drums after measuring and there was a difference.
I looked into the hand brake unevenness and found that the shorter cable side needed fixing.
On the lever that the cable attaches to on the shoe, there is a pressed out part that acts as the stop. The arm was loose at the pivot point at the top and the pressed out part was resting past the correct resting point. With the aid of my wingman Paul.H we swapped over this lever and the cables are once again even.
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Ben_nz · Posted: Sat Aug 16, 2008 12:28 pm Post subject:

You're doing better than me then.
I opened up the weaker brake drum to sand / lubricate / adjust, and I finally worked out how the brake adjusters are supposed to work and why they don't. Laughing

Then I reassembled it, went and did a lot of hard stops in forwards and reverse, loaded up the boot with batteries and went for my retest. The strength of the rear foot brakes was more even but not enough to pass.
Now the car has gone to the mechanic, who says the problem will probably either be a brake hose or that trusty brake bias valve.
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Hey Ben, sorry to hear that, were your shoes in good condition?
If your rears are working but not well enough I would check the cylinders are lubricated and not stiff. If they are ok I would then check the compensator by cable tying the sprung load away from the compensator, if it is working you should get less brakes on the rear if there is no change then I guess it’s seized, can these be lubricated?
I now have 1 more brake test to see if they will pass if not then I will try new shoes and if it fails again then I will have to get new drums I guess.
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Ben_nz · Posted: Mon Aug 18, 2008 9:46 am Post subject:

All the shoes and front brake pads were replaced about 7 months ago.
Today I got the car back from having the brake bias valve replaced ($$$) and it didn't have any effect on the rear footbrake balance! Infact the imbalance was slightly worse than last time - 27% difference.
The guy at the testing station suggested swapping the drums left to right, so I did that tonight and I'll go back tomorrow to try again. Rolling Eyes

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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Ben, check both the pistons on both cylinders.
Remove 1 drum and get a friend to slowly press on the brake pedal, both pistons should move out, you should be able to see if the self adjustment is working. If the pistons don’t move, or one is stiff, see if you can remove the rubber cover and clean / lubricate, failing that replace the cylinder. Check the other side in the same way. I had an imbalance due to a brand new cylinder on one side and a sticking one on the other side. Paul.H and I noticed that my old one had rust coming out of the seal, so we used the other from his axle and now both are equal albeit not good enough.
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Ben_nz · Posted: Tue Aug 19, 2008 2:08 am Post subject:

That's the first thing I did on the weaker side, and I couldn't see any problems.
Latest news though, swapping the drums reduced the imbalance from 27% to about 13% and I passed! Very Happy

If only I had known to try that first. Confused

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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

sweet, well done, wish me luck lol
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

well i had mine retested and the hand brake is more powerful than the foot brake, balance is ok! What do i do now? Changing the rear brake bias valve made no change for you Ben, did the bit on the compensator, that rested on the sprung load rotate? I might try and see if it has seized but im not sure if it only goes in and out. i dont want to waste my time changing it if it made no change for you Crying or Very sad

i am now stumped as the shoes have pleanty of meat on them?
suggestions anyone?
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Ben_nz · Posted: Thu Sep 04, 2008 2:13 am Post subject:

The brake bias valve didn't change the left/right balance problem on the rear footbrake; that was cured by swapping the outer drums over.
But in hindsight the bias valve did seem to achieve a bit of an Alfa miracle - the car can now lock its front wheels under hard braking instead of one or both rear wheels.
I never checked whether it was seized myself, because I thought I'd have to disconnect the panhard rod (?) and I couldn't be bothered. Wink

I'd say your problem is more likely than mine to be related to the bias valve thingy.. unless maybe one of your brake lines is crushed or full of bubbles.. actually I have no idea what I'm talking about. Rolling Eyes

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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

Is it normal for our brakes to be pants? Should they lock the rear with foot brake or handbrake when being tested, as they are put under much higher load?
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Admin · Posted: Wed Sep 17, 2008 10:54 pm Post subject:

Hi

Never had any issues with a 33 locking the rear up first. Fronts manage to lock up first (not that the brakes are that good).

All the best

Keith
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

hey keith, i think you mis understood me.
When the brakes are working as they should, are they good enough to lock the rears when using the foot brake and the handbkare on the brake tester?
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Admin · Posted: Sat Sep 20, 2008 8:43 pm Post subject:

Hi

Not sure. On MOTs I am not sure I have locked the wheels on a car.

All the best

Keith
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Ben_nz · Posted: Sat Feb 07, 2009 12:04 am Post subject:

Well, 6 months later both my cars were due for WOFs again.
And both of them failed because the rear footbrakes are out of balance! Aaargh! Evil or Very Mad

Handbrakes are fine on both cars.
In both cases it's the right rear brake that is the weaker.
I guess to start with I'll swap the drums over on both cars and take them back to try again.
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

ben
before you do that why don't you undo the handbrake cable inside the car and then adjust the rear brakes with everything insitu through one of the wheel bolt holes.
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Ben_nz · Posted: Sun Feb 08, 2009 6:11 am Post subject:

I thought that even if the brake shoes were adjusted closer to the drum on one side of the car than the other, the brake system would still apply the same amount of force on each side?
More fluid would have to flow into one side than the other to move the more distant shoe further, but once all shoes have contacted their drums they all have the same system pressure behind them. Is this wrong?
If it's not wrong, why will adjusting the brakes help?
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BigAl · P4 Joined: 06 May 2003 Posts: 2990 Location: U.K Surrey

I think that the system is a x split system design so that one side is not dependant on the other side, so that if one side fails the other will continue to work.
I think that the difference in brake force has come from the automatic brake adjuster working/working better on one side.
Over here the nuts are no longer available from Alfa, so its another incentive not to remove anything unless necessary.
I do this just before every mot and when i feel the brake pedal has lots of travel in it before it goes hard, which is now, lol Laughing

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