Uneven brake ware 4200 cc

[davidhowson]

Hi Guys

Quick question:

Any thoughts what may be causing me to have a half inch band round the outer edge of my front off-side brake disc?

I have noticed that there is a rusty band which doesn't clear no matter how much braking I do. I Cleaned off the disc and took out the pads and cleaned them and copper-slipped them back into the caliper but the band is re-appearing.

Clearly the pad on the outer face isn't pressing against that part of the disc but I can not see why, the pad surface is flat and clean and the car stops ok.

Any thoughts what else I should check / change? Could it be that I need to flush through the brake fluid? All 4 pots seem to move ok so not likely to be a sticky caliper.

Thanks!

David

 

[BennyD]

David, in my experience it usually happens when the discs need replacing. I think corrosion gets deep into the disc face from the edge and doesn't seem to clear with use. I recently had the same thing with my BM, I changed the discs and they are wearing normally again. This seems to indicate that whatever caused it, it wasn't the callipers. Fortunately, thanks to the good work of the guys on this forum, replacing the discs and pads needn't cost the earth anymore.

 

[davidhowson]

Thanks for the reply Benny, but the discs were new last year and less than 2k miles on them, so I hope it's not that!!

I'm wondering if I chnaged the fluid in case there's uneven pressure due to contamination or age.

I'm also running Green Gripper pads and maybe it's them?

Thanks tho'

Regards

David

 

[davy83]

do you get the same band on the inside surface of the disc? or is it clean or even rusty at the ID of the inside face of the disc?

This is pretty odd as usually the face of the pad wears down to the shape of the disc, so for some reason the pad is not being pushed all the way into the disc? How long have you have these brake pads on there? is it possible you just have not allowed enough time to let them bed in yet? Especially if they are hard material. Or maybe not breaking hard enough to get them bedded in?

 

[BennyD]

When you cleaned the disc surface did you manage to get back to shiny metal or was there corrosion still present? How about a photo David? That way someone might have the definitive answer as I am wracking my brains and can't think of an obvious one.

 

[Emtee]

The pads do sit within the braking surface of the dsk. Not half an inch mind you, more like 5mm.

 

[BennyD]

M, from what David was saying it is only the front offside disc that is affected and why that would be, I just don't know.

 

[ENZ525]

Does sound like uneven pressure if it is one corner doing that...maybe try bleeding before changing the fluid...

 

[BennyD]

TBH Enzo. I don't see how it can be uneven pressure. Surely, if the pistons push out of the calliper square, and that's the only way it can due to the design of pistons and cylinders, the pressure must be the same across the back of the pad for the whole of the surface of each piston. The fault, IMO, has to lie in the contact area between the disc and pad. On my wife's BM the rear brake pads had a chamfer on the top and bottom of each pad and didn't contact the surface until the pad had worn down sufficiently, but why it would do this only on the front O/S I don't know.

 

[conaero]

I have seen this quite a lot on our Masers, so much so I talked to Mike Roberts about it. From what I can fathom, it would appear that the pads are binding in the calipers and filling the edges might be the answer.

I happend alot on my old 3200, and usually appeared after the car had been sat and not used much.

If the discs are new, I would whip them out, clean, clean the guided, and file the edges of the pads so they drop in, remembering to put a blob of copper grease on the back to stop them rattling. If that does not work, the problem would exist within the caliper, see if you can move it in and out easy. My 3200 was very stiff and Mike said I need either a new caliper or replace the piston o rings. Incidentally, I had a similar issue on my classic Opel GT and changing the o rings made the braking like new again.

 

[davidhowson]

Thanks for all the replies guys!

It is just the outer surface of the offside front disc that is affected.

I wondered if the pad material had either come off the backing and slipped or if a bit had broken off, but the pad looks to be in as new condition, and I swapped the pads over inside face to outside face when I cleaned them up.

The pads were a bit of a tight fit, so I filed a little bit off the edges and put them back in with copper slip. I didn't take much off and they were still quite tight fit. Maybe that's all it is.The discs and pads were changed at the same time just a few months ago, but I didn't use the car very much between November and March and again these cars really don't do sitting around very well even in a garage!

The band of rust is perhaps not a wide as it was this time, so Matt is onto something with the pad perhaps not moving freely in the caliper.

I think I will get the fluid flushed through as well just to make sure.

Any recommendations on fluid if I swap this??

Thanks again guys, I will let you know what happens.

Regards

-David-

 

[Parisien]

Wasn't there an issue of caliper corrosion and a plate lifting off?

Do have to make sure a snug fit after the 45 min filing of the old greengrippers!!!


P

 

[conaero]

Frank there was indeend.

Also the pads should drop in so I would file a bit more off.

 

[conaero]

As for fluid being a performance car it's probably Dot 5, but dot 4 is probably fine. Just don't mix them make sure you flush all the old stuff out as the shouldn't be mixed.

 

[RonnieMack]

Hi David,
The handbook recommends synthetic DOT 4 fluid and I would suggest it's best to flush out and replace the fluid every 18 months or so.
Cheers
Ronnie

 

[conaero]

Hi David,
The handbook recommends synthetic DOT 4 fluid and I would suggest it's best to flush out and replace the fluid every 18 months or so.
Cheers
Ronnie

Yes I would stick to the dot 4, I have not heard great things about dot 5.

 

[Fluxy]

Interesting post - I've noticed the same thing on mine. New discs with Greengripper pads too - I've also noticed the ABS kicking in a little earlier than you might expect, although this might be due to the shocking suface at the end of my road!

Might have to have them out and file em off a bit more.

 

[davy83]

I also had problems with brake pads needing modified to sit well in the caliper.

Thinking about this, if the pad was binding at one spot it would tend to make the pad rotate as the caliper piston applies pressure to it, producing the uneven wear, it would also tend to just rotate more as the pad wears resulting in one piece of the disc not being touched.

I think filing a bit more off the pads is in order!! you are looking for high spot so make sure your filing is flat, if possible, you want a little movement between pad and caliper but a snug fit so its not loose. If your filing off is not parallel to the chrome surface in the caliper the pad may rock in use which wont stop it working but cause some vibration (although i have not seen this)

 

[hodroyd]

Disc Pads should always move freely in their guides and not be stiff, otherwise they will potentially jam in the guides and incorrect braking follows..!!