Astra rear brakes, routine replacement = rubbing + squeek

[kaytay]

I am hoping that I am being blatantly blind to an obvious solution to this, bear with me there’s a lot of info here:

Astra 1.7TDI, 2000 reg. 100k miles
Routine inspection of rear brakes inspired me to replace the shoes, since the drums were lipped and new ones were only £30 pair I decided to replace shoes and drums together. Prior to this there was no breaking noise, the hand brake functioned fine on both sides and the footbrake function was also sound, passing its MOT with ease.

Having replaced shoes on other cars before this is not my favourite part of servicing but I'm happy and confident to do it.

I stripped and cleaned down the back plate, springs etc and swiftly assembled the new shoes in place, putting everything back where it came from. The wheel cylinders look fine and dry and their pistons slide freely. With the handbrake cable slackened off I pumped the pedal, heard the adjusters ratchet to position. Spinning the wheels (both sides) resulted in a localised rub through about 20 degrees the rest of rotation freely. I expected some rubbing while they bed in, I adjusted the handbrake stop nut but didn’t tighten it all the way down to its final position so not to unduly load the brakes while they bed in

A short test drive resulted in brakes and handbrake functioning well, silently. However a longer drive of 5 miles resulted in loud pulsing ‘rubbery, squelchy’ squeak under heavy breaking conditions, from the rear brakes. This was accompanied by slight pedal sensation similar to that related to warped front discs. The brakes still function fine.

Strip down revealed nothing suspect, everything was still in place, wear was moderately uneven on the shoes but nothing unusual for new parts. There was no shiny evidence of something contacting something it shouldn’t.

Backing the adjusters off and slackening the handbrake made no difference, so as there seemed to be no detrimental fault other than the noise I decided to treat it as just needing to bed in. Having done about 50 miles including plenty of irregular braking the noise persists and still there is no evidence within the drums that anything is wrong.

I have stripped and re assembled both sides putting a spot of copper lube here and there, rubbed down the ‘high spots’ on the shoes and re adjusted everything today. No difference.

It is as though the drums are not round, or perhaps the holes not concentric so I have compared old and new, their drilling s look the same.

Someone throw me a line please…..

 

[iain90210]

A few thoughts which may/may not be helpful:

1. I have just looked at renewing brake drums in one of my workshop manuals. It says 'use a suitable solvent to remove any preservative that may have been applied to internal friction surfaces' This could explain the squeal. Maybe the rub is due to bedding in as you thought.

2. Do you trust the new drums? Are they brand new and of a good quality? If not brand new are they slightly oval - you would need a micrometer to measure this. OR:

3. I would consider putting the old drums back on. A b*ll ache, I know, but if the problem is cured you will know what the cause is.

Good luck and enjoy

Iain

 

[keyplayer]

You could try swapping the drums around.

 

[kaytay]

Thanks guys,

The drums and shoes are new, unipart branded, from a unipart shop so I feel I should be able to trust them.
I have no means of testing their roundness or concentricity - I do have a mic but is that not only going to tell me the drum wall thickness which could be uneven without affecting the truness of the machined surface inside?

The new drums were covered in preservative oil which i removed with solvent and cleaned down with aerosol 'brake cleaner' so I'm confident they are clean

If i refit the old kit and the same happens - any ideas in advance ? wheel bearing wobble ? not that theres any sign of this

unless there are any more posts, my next steps (when it stops raining) will be:
swop the drums over and test,
refit all the old kit and test
assuming old work ok - fit new drums on old shoes, if this is ok its the new shoes that are at fault and I'll get another set of shoes .......

I hate brake drums

 

[iain90210]

I do have a mic but is that not only going to tell me the drum wall thickness which could be uneven without affecting the truness of the machined surface inside?

Sorry I should have specified, an internal micrometer. Anyway, as the drums are brand new I wouldn't think this should be an issue.[/quote]

 

[yes2mud]

kaytay,having read through your posts,you seem to have done a thorough job and already checked likely causes.I have had the odd brake drum out of round from brand new.This is your most likely cause of pedal oscillation.If you have a brake pipe clamp,you could fit it to the rear flexi hoses one at a time,this would stop that brake working and tell you which side has the judder problem.This was how I found out the same problem on our last astra.Alternatively,if you know anyone in engineering,who could loan you a DTI (dial test indicator).You just fit the drum backwards onto the hub,set up the DTI on a firm base and rotate the drum slowly looking for runout.I clamp a DTI mounting stick to an axle stand this works ok.

 

[kaytay]

i've not been able to get near the car today but if theres no rain in the morning I'll be on it doing what i stated earlier as soon as....

I know where I could get a DTI but not till next weekend and would need to take the drums back for a swop before then. if the old ones function fine when i put them back on tomorrow (ill be tempted to leave them) but will take the new drums back and take it from there ......

Thanks guys, watch this space for the result

any other ideas - lets be having them, I despair, the central heating boiler has come out in sympathy for the car, it's developed a noise, oh the joys .....

 

[kaytay]

well, Ive swopped the drums and the noise / sensation continues exactly as it was from both sides

Note: they were fine and silent under initial gentle braking, when i heated them up with a bit of left foot braking the noise then happens everytime.

So heat is the enemy, perhaps something has a very snug fit and the heat just makes it that fraction too big. But theres nothing shiny or destroyed (other than the proper friction surfaces) to suggest a source for the contact problem.

I think im going to have to strip one side and compar everything in minute detail with the old kit, its lashing it down again and im really loosing the will.....

 

[johnwr]

Hello kaytay, If I were you I would refit the old shoes and drums, but this time manually adjust the brakes, I know it is difficult with worn drums, but relying on the auto adjuster you will lucky to get the adjustment very close to the drum. If this works then you should try refitting the new shoes and drums and again manually adjusting the brakes. If the noise and judder still occurs then return them to unipart. Checking the drum with a DTI will be difficult because I believe there is a lip on the drum flange, if the drum is not fitted perfectly in the reverse position then the DTI reading will be meaningless. It is also impossible to check anything but drum size with an internal micrometer.
I hope you have some success with your problem, keep us informed.
regards johnwr

 

[cabot]

Sorry to butt in but have unipart supplied the correct size of drum .I tried a few non vauxhall parts suppliers and they seemed to be a bit unsure of exactly the same part.I went to vauxhall and there was no confusion about the size of the drum. I changed them,have had no squeals or rattles and have had my astra for 7 years. Price wise they were the same price as the non vauxhall dealers.And no i dont work for Vauxhall!

 

[iain90210]

It is also impossible to check anything but drum size with an internal micrometer.

regards johnwr

Measure the internal diameter. Then take another measurement at right angles to the first. Compare the two, they should be identical. Repeat, taking pairs of measurements around the drum. This will tell you whether or not the drum is the correct size and if there is any ovality.


Only problem is that not many people have an internal mic in their tool box!

 

[johnwr]

your right iain, a bit of brain fade, what I meant to say that you can't check for run out with an internal mic.
regards johnwr

 

[Bluebee]

I have the same problem (1.7 DTI Astra Van). It started when I serviced the brakes, nothing required changing, just a good clean and put back together. Initally everything was OK, then after about 10 miles a oscillating noise (feeling) from the rear n/s drum. I then replaced the drums and shoes still the same. Everything is clean and when I take the drum off to have another look, the adjuster have worked. The only thing I can think of is that the origional drum which is making the noise was difficult to get off, and i had to get a large screwdriver between the drum and back plate and tap the drum with a hammer to get it off. Could the back plate be slightly out of shape. I'm a bit reluctant to replace it as I can't see why that would cause the oscillation. Any ideas or thoughts would be appreciated.

 

[Trazor]

I would suggest you raise this problem as a new topic, as this one is nearly 2 years old, you will get a better response.