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MG MGB Technical - Brakes squaling
|A new season has started for me and my 64 B. Most things are OK or even perfect this season ( se next thread) but i still have a VERY annoying brake squeal. It is persistent and on the RH front wheel only. |
The car is fitted with the dimpled and slotted discs from MGOC. I have been through greenstuff pads, soft Mintex pads plus another cheapo soft brand, anti squeal glue-on patches, copper paste, sticky Loctite special anti squal expensive compound, and yes - the piston slots are positioned correctly. Still, the RH front wheel squeals like an old army truck, but only when light pressure is put on the pedal. Slow city driving really isnt fun!
As far as I can understand the problem must be with either the disc or the caliper or the alignment between the two.
Has anyone got some good advice or proven solution before I go ahead and rip things apart? (I have been through all the archive threads on the subject)
|Jan Emil Kristoffersen|
|Jan, I had exactly the same problem as you describe with brake squeal on the right hand front wheel. Like you I fitted slotted and dimpled discs (and new calipers) from the MGOC and greenstuff pads, swapped them for Mintex, still no difference. Checked the run out of the disc and the bearing play - all ok? Used the sticky brake pads and copper grease on the back of them, checked and lubricated the pistons on the brake caliper and still no luck! Looking at the pads each time I changed to a new set, the sticky brake shims were worn through by the brake caliper piston and there were wear marks on the top and bottom of each pad (where they had been chattering in the caliper I guess). I tried to get stainless steel metal shims, but they don't seem to be available for a MGB. |
In the end after years of frustration (yep years) I thought I would just try the pads without any sticky shims on the back and just used copper grease on the back and top and bottom edges. This worked for me, not a hint of noise now :-)
When you changed the pads did you de-glaze the disc? I'm not a fan of Greenstuff but I have previously had a similar problem on a midget which started when I changed pad manufacturer. I assumed it was down to the slightly different composition of the friction material and was cured by a thorough de-glazing. But why one side and not the other?
Are the slotted discs handed? One would assume, unless the slots are perfectly radial, that they should be.
This is quite a common problem, I tried every thing I could think of to stop this problem but nothing I did lasted very long, until I got hold of some anti squeal shims from a Peugeot expert, which have done the job, I have been to the Alps quite a few times in my car since, driving up and down some of the biggest mountain passes in Europe, and not a peep,A.T
|Andy, do you have the Peugeot part number for those shims? I'd be interested in having a look at them. Thanks|
|I believe the anti squeal shims are not that easy to get (in the UK) ?806 model?|
Another thing worth trying is anti squeal stick on patches on the top /bottom edge of the backplate. The rationale is that when braking the pads can move upwards within the caliper and possibly chatter. Eventually the gap in which the pads sit get fractionally bigger. If a patch works for a while (as it must wear thru like the ones at the piston,) it might be a clue.
It might also be worth swapping the pads from one side to the other. It has been known to cure the problem, tho why is less well known!
|It's not a trivial task but in desperation you could try swapping hubs (and hence discs) between sides as various makes of pad have all squealed on the same side. Parts Catalogue shows quantity two of both hub and disc so they are not handed.|
You would have to reset the end-float on both sides.
After trying many things to cure it on the V8 the last was to put offcuts of the sticky pads on the top and bottom edges of the pad back-plates, having previous stuck the main part of the pads to the back of the pads. As with most things tried they were initially quiet, then started making slight noise, but only for a very short period and since then (many months) they have been quiet. The interesting thing is that these sticky pads are a couple of mm thick, but there was room to get the pads in - with a bit of a wiggle - which implies the clearance to caliper is significant. Removing the pads shows the piston had cut into them (hardly surprising) and the strip on one edge of a couple of pads had moved to one side, but still no squealing.
|Thank you for all your suggestions. It seems I need to focus on soft shims and/or copper paste on the top and bottom edges, and maybe deglaze the discs. BUT: How do I deglaze discs? Wet sanding paper or grinding paste? |
I have a set of new plain (cheap discs from Moss) discs on the shelf. If the aforementioned fixes do not cut the mustard I will probably swap discs. Swapping hubs sounds more like an autumn/winter job to me.
|Jan Emil Kristoffersen|
Are the discs on your car asymmetric? Therefore handed, if so are they installed correctly? De-glazing is not easy on the inside of the discs but one way could be by glueing a piece of emery cloth to an old pair of pads and rotating the wheel with light pedal pressure. Never tried it though!
|I am sorry but I don't the part number for the Peugeot anti squeal shims, by the way you need 4 of them, definitely the best fix I have come across for this problem,AT|
|Allan, One trick of the trade is to put a suitable sized ring spanner over a wheel stud, then screw on the wheel nut fairly tight, then you can spin the disc at a reasonable speed. If you can find some 3M 60 grit emery cloth thats coloured green then that was the best I have used. Make sure to use some brake cleaner to clean off and dust etc.|
PS when spinning the disc keep your fingers away from the gap between the hub and the caliper, it hurts like hell.
|Unfortunately, this an all too common problem with disc brakes in general. What you're hearing is the pad occilating inside the caliper as the it begins to make contact with the rotor. Almost every new rotor, that I've handled, is out of round right out of the box. Even the best ones. I usually take a light cut out of them on the lathe to make them true. However, this process leads to another problem; lateral runout. This lifts and then lowers the brake pad, in relation to the rotor, causing the brake squeal that we've come to know all too well. 3M makes a kit that is designed to remove the lateral runout left over from the cutting process on the lathe. It consists of a drill mounted disc that accepts 3" sanding discs especially made for this application. A few minutes working on each rotor will almost always quiet the offending rotor. I've had great success with it. RAY|
|Just noticed that some new V8 pads have significant chamfers on leading and trailing edges, never had that on MGB discs before.|
|Paul, that feature is very common on most of the disc brake pads, that I have installed, on many different cars. a I agree that I've never seen it on a B pad though. Even on B V8 pad. RAY|
I chamfered the edges of the friction pads, painted the edges of the backplates with two coates of Plastidip, put on new anti squeal pads, coated all around the edges + on AS pads with copper paste, including springs and cotter pins.
Same noise. No improvement what so ever. Arrrrrgh!
|Jan Emil Kristoffersen|
|Jan, have the offending rotor cut on a lathe. Removing just a small amount of metal can make a world of difference. The brake pads are lifting and falling back into place, causing this noise. I've encountered it more times than I can count. RAY|
|Thank you Ray, the lathe way is the next step. I hate doing such jobs in May!|
|Jan Emil Kristoffersen|
|Jan, as I said I tried every thing I could think of which included skimming the front discs, as long as you don't have wire wheels a lot of garages have a brake lath so it can be done on the car, both sides in less than an hour, but it didn't make any difference within a few days the noise was back, A.T|
|As I posted earlier, simply skimming the rotor can leave behind a lateral runout that allows the pads to move around the face of the rotor, causing the brake squeal. By removing this runout, using a small circular sanding disc, the noise should go away. RAY|
|Ray, I assume you are not familiar with the on the car brake laths, which I am surprised about as the best ones are made in the US, they are fitted with a very smart gyroscope which eliminates any run out, on the discs, when they are being cut,which also takes into account any run out due to faults in the hub, drive flange etc,A.T|
|Andy, the problem with all brake cutting lathes is that they leave behind a spiral mark from where the cut was started. This occurs even with the smallest cuts, done at the slowest speeds. This is where the 3M sanding discs come in handy. They leave behind a circular pattern on the rotors which eliminates the the spiral. The rise and fall of the brake pads, as they come into contact with the rotor, is eliminated. RAY|
|Article in this month's MGOC magazine that suggests that particularly with upgraded systems, a non-compatabilty of disc to pad material results in insufficient heat being generated. This can cause squeal. Easy enough to test. My pal's V8 squeals when tootling around town, but is fine when used from a decent speed.|
|The Peugeot shims are no longer available - I checked this with my local Peugeot dealer a couple of years ago.|
The MGOC are usually looking for something new to sell us, perhaps they should get some of these things made - I'm sure they'd sell enough to make it worthwhile.
what you said is most interesting, but if what you say is correct then surely this would be the same in all cases, and all cars would have a brake squeal after the discs had been skimmed and not dressed with 3M sanding paper afterwards, I don't know how many discs you have skimmed using an on the car brake lath, but I have skimmed quite a few hundred, and have never had a brake squeal on any except my B, and have never dressed the discs afterwards with any kind of sanding discs in my opinion the problem lays in cheap brake pads, in the UK you can buy a set of pads for between £10-00 and £15-00, which is ridicules, you go to a main dealer and try to by a set of pads for £10-00, for a modern car, A.T
|Milling the discs in situ proved to be difficult locally. Last night I was so tired of scaring the s.. out of pedestrians that I tore off the slotted and dimpled discs and the green stuff pads and replaced them with new plain discs and standard pads. Anti squeal pads and copper paste on the piston side of the pads. 20 miles test drive and bedding in the brakes as per instructions. Not a sound - just noiseless stopping power. |
I hope it will last :-)
Thank you for all your suggestions,
|Jan Emil Kristoffersen|
This thread was discussed between 20/04/2016 and 19/05/2016
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