Hi everyone
I am having issues with my brakes (95 XM 2.5TD saloon). When I got the car the brakes squealed badly and looked quite worn so I decided to change front discs and pads (in June). By November the brakes were juddering when braking from speed (with those humps before roundabouts/junctions the shuddering was quite bad). Assumed that the brake discs had warped. The discs were replaced under warranty and now I have new discs (same pads as before - bendix). When replaced I got no judder for a while. Guess what (under 1,500 miles later) brakes juddering again. Noticeable from 50mph up although not always bad (sometimes light shudder). Discs warped again? Could something be causing the warped discs or is it just the quality of the discs? These ones are Brembos. I do get a slight squeal when the car pulls up - might just be dust? in this colder weather? Could the calipers be sticking?
Thanks
Andrew
Brake judder
Moderator: RichardW
Do you sit with your foot on the (foot) brake at traffic lights and at junctions. That can warp modern disks if they are hot, as can failure to torque the wheel nuts evenly with a torque wrench.
Try cleaning the disks with brake cleaner, and refitting the pads with the backs coated with Copaslip. That should help the problem with the current disks squealing.
I've got bendix pads and brembo disks on my ZX, they're fine.
Try cleaning the disks with brake cleaner, and refitting the pads with the backs coated with Copaslip. That should help the problem with the current disks squealing.
I've got bendix pads and brembo disks on my ZX, they're fine.
A question has to be asked, when you fitted your new pads and disc's. Did you run them in or just carried on from the word go braking harshly as normal. Which then could cause your disc's to warp, because the disc's are still rough and will generate alot of heat.
Otherwise are your wheels balanced.
Sooty
Otherwise are your wheels balanced.
Sooty
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first-things-first
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Thanks for your replies.
arry_b - as a rule I do not "ride" the footbrake or clutch. Being an XM I usually hold on the clutch on slopes or sometimes use the brake. I do take care to tighten the wheel nuts in the right order (diagonals). The discs were cleaned using thinners after being fitted to remove grease/dirt. The pads have copper grease behind them (small amount on wear areas only). As regards the noise, maybe I should elaborate more, what I am talking about is not a more continual squeal when braking but what I would class as more of a binding squeak at the last moment when the car comes to a complete stop.
sooty - I don't believe I am a harsh braker as every other car I have owned has never suffered from warped discs. Maybe I did not take as much care - are XM's overly sensitive to running in due to the power brakes and the car's weight? I did have a Xantia directly before and didn't suffer from warped discs and had that car 60K miles and changed discs and pads.
Thanks both for your answers
Andrew
arry_b - as a rule I do not "ride" the footbrake or clutch. Being an XM I usually hold on the clutch on slopes or sometimes use the brake. I do take care to tighten the wheel nuts in the right order (diagonals). The discs were cleaned using thinners after being fitted to remove grease/dirt. The pads have copper grease behind them (small amount on wear areas only). As regards the noise, maybe I should elaborate more, what I am talking about is not a more continual squeal when braking but what I would class as more of a binding squeak at the last moment when the car comes to a complete stop.
sooty - I don't believe I am a harsh braker as every other car I have owned has never suffered from warped discs. Maybe I did not take as much care - are XM's overly sensitive to running in due to the power brakes and the car's weight? I did have a Xantia directly before and didn't suffer from warped discs and had that car 60K miles and changed discs and pads.
Thanks both for your answers
Andrew
I know the noise you're talking about. One of my bikes does it when the pads get dirty. I clean them up by rubbing the faces on a bit of sandpaper laid on a flat surface and clean up the disks with brake cleaner. I also chamfered the leading edges of the pads which has helped.
I have used Lucas anti-squeal in the past on troublesome cars. This is a thick blue gooey liquid which effectively glues the pads to the pistons. It does work, but it's a bit of a bodge really.
One other thing to check is that the hubs are spotlessly clean and rust free where the disks bolt onto them.
Incidentally, after I had to pay for a new clutch in my XM V6 (11 hours labour!) I stopped holding it on the clutch on hills
I have used Lucas anti-squeal in the past on troublesome cars. This is a thick blue gooey liquid which effectively glues the pads to the pistons. It does work, but it's a bit of a bodge really.
One other thing to check is that the hubs are spotlessly clean and rust free where the disks bolt onto them.
Incidentally, after I had to pay for a new clutch in my XM V6 (11 hours labour!) I stopped holding it on the clutch on hills
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Stuart McB
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first-things-first
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Thanks again for replies. I think I will check run out again and see if they are warped. When I got the car I changed the front tyres, had all four balanced (did have a bad wobble caused by wheels not being balanced) and have had a wheel alignment.
So I would hope the balance is not out (about 5K 6 months ago). Although I think I heard the exclusive (speedline) 15 inch alloys can go out of balance easily - anyone confirm?
Thanks
Andrew
So I would hope the balance is not out (about 5K 6 months ago). Although I think I heard the exclusive (speedline) 15 inch alloys can go out of balance easily - anyone confirm?
Thanks
Andrew
Andrew -
You seem indeed to be an experienced DIY'er - knowing the pitfalls doing the brakes.
Technically the XM brakes are basically the same design as found on the BX & Xantia - being a beefed up version. Also these models have the same basic front supension setup (McPherson strut).
The only thing special to the XM regarding brakes - is that the XM is a heavy vehicle compared to other Citroens - imposing much higher load on the brakes.
It's similar to the CX compared to other Citroens in it's era.
But from own experience I know that the CX brakes is of a totally different design - with an insane handbrake construction (requires manual service/adjustment every 3600miles to be usefull).
I've never experinced strange problems with the CX main brakes.
Therefore I think your XM brake problems may be similar to what I have experienced from the BX - which for economic reasons allways have been quite worn species in my herd of cars.
The McPherson strut design means you only have the lower control arm fluid blocks (rubber busheings) controlling the longitudinal front wheel position. Therefore these fluidblocks are opposed to immence forces during their service life. Even slightly worn lower fluid blocks makes for unwanted geometri on the lower control arm - imposing slightly different forces on the front brakes & wheel bearings. This can indeed make for strange symptoms during brake actions.
To follow up on the very fine observations above on how to prepare discs & pads - I've experienced another common problem with brake pads in general : the back coating (paint) thickness. This works as squal dampers - even prevents the pads oscillate against the disc surface during braking - a very common problem.
It's the oscillating pads hammering against the caliper body that makes the noise - wether being a high pitch or groaning.
This is perfectly normal for brake pads - in many cases only perfectly matched discs & pads materials & surfaces can prevent this.
But even high cost "quality" branded brake parts are NO guarantee - as the operating conditions on any vehicle is the main factor.
In fact my only experience with these high cost quality parts are reluctance to brake fading when harsh driving is the issue.
Guess that's why they commonly are referred to as "performance" parts.
These parts simply takes the heat a lot better.
The use of pads with a thick layer of back coating allways have worked best for me. Just doing up the brake service replacing parts as backbone job - I often forget about the pads coating. Sure enough - if the brakes then starts squaeling - an inspection reveals pads with no backcoating - just a thin stain protective coating.
Driving on with these pads - the sqealing then tends to evolve into brake judder - as there seems to develop "spots" on the discs surface - seemingly from heat differences during braking. This is definately the case if any suspension details are worn - making for unwanted geometry during braking.
Brake problems on my cars then have lead to other faults being the issue - i.e. the fluidblocks and a worn wheel bearing.
I had no problems re-using the brake parts doing as mentioned above resurfacing the parts - and using a separate squeal damper padding behind pads thinly coated.
Andrew - I know this is a long talk with no definate answers to your XM brakes problem - but my hope is that you get some ideas.
You seem indeed to be an experienced DIY'er - knowing the pitfalls doing the brakes.
Technically the XM brakes are basically the same design as found on the BX & Xantia - being a beefed up version. Also these models have the same basic front supension setup (McPherson strut).
The only thing special to the XM regarding brakes - is that the XM is a heavy vehicle compared to other Citroens - imposing much higher load on the brakes.
It's similar to the CX compared to other Citroens in it's era.
But from own experience I know that the CX brakes is of a totally different design - with an insane handbrake construction (requires manual service/adjustment every 3600miles to be usefull).
I've never experinced strange problems with the CX main brakes.
Therefore I think your XM brake problems may be similar to what I have experienced from the BX - which for economic reasons allways have been quite worn species in my herd of cars.
The McPherson strut design means you only have the lower control arm fluid blocks (rubber busheings) controlling the longitudinal front wheel position. Therefore these fluidblocks are opposed to immence forces during their service life. Even slightly worn lower fluid blocks makes for unwanted geometri on the lower control arm - imposing slightly different forces on the front brakes & wheel bearings. This can indeed make for strange symptoms during brake actions.
To follow up on the very fine observations above on how to prepare discs & pads - I've experienced another common problem with brake pads in general : the back coating (paint) thickness. This works as squal dampers - even prevents the pads oscillate against the disc surface during braking - a very common problem.
It's the oscillating pads hammering against the caliper body that makes the noise - wether being a high pitch or groaning.
This is perfectly normal for brake pads - in many cases only perfectly matched discs & pads materials & surfaces can prevent this.
But even high cost "quality" branded brake parts are NO guarantee - as the operating conditions on any vehicle is the main factor.
In fact my only experience with these high cost quality parts are reluctance to brake fading when harsh driving is the issue.
Guess that's why they commonly are referred to as "performance" parts.
These parts simply takes the heat a lot better.
The use of pads with a thick layer of back coating allways have worked best for me. Just doing up the brake service replacing parts as backbone job - I often forget about the pads coating. Sure enough - if the brakes then starts squaeling - an inspection reveals pads with no backcoating - just a thin stain protective coating.
Driving on with these pads - the sqealing then tends to evolve into brake judder - as there seems to develop "spots" on the discs surface - seemingly from heat differences during braking. This is definately the case if any suspension details are worn - making for unwanted geometry during braking.
Brake problems on my cars then have lead to other faults being the issue - i.e. the fluidblocks and a worn wheel bearing.
I had no problems re-using the brake parts doing as mentioned above resurfacing the parts - and using a separate squeal damper padding behind pads thinly coated.
Andrew - I know this is a long talk with no definate answers to your XM brakes problem - but my hope is that you get some ideas.
Andrew,
If you're clutching at straws you might find this useful:
http://www.andyspares.com/discussionfor ... IC_ID=3240
If the brakes are binding it would cause overheating and eventual warping.
Only a thought.
cheers
noz[8D]
If you're clutching at straws you might find this useful:
http://www.andyspares.com/discussionfor ... IC_ID=3240
If the brakes are binding it would cause overheating and eventual warping.
Only a thought.
cheers
noz[8D]