Brake disc, is this normal?
Discussion
|https://thumbsnap.com/Ty7epk5U[/url]
Smint said:
The wedge shape that brake pad has worn to doesn't look in the least right to me, i'd be having those pads out and see what the dickens is happening in there.
Totally agree, nothing normal about that at all. The disc may not yet be dead but that pad's close to giving up and I suspect the two are related. If it was my car I'd be getting ready for a set of discs and pads. No point putting new pads on that old disc. If the car still has adequate braking and stops in a straight there may be no immediate rush so long as you keep an eye on things. I'd start by taking the car somewhere quiet and braking all the way to anti-lock. See what happens.
To add: it looks to me as though OP has a partially jamming piston in that calliper, so it may well need a new calliper as well. They're not expensive on most cars these days and few garages will bother to attempt a refurb. (i.e. new piston and seals, which may or may not be a complete repair.)
Panamax said:
Smint said:
The wedge shape that brake pad has worn to doesn't look in the least right to me, i'd be having those pads out and see what the dickens is happening in there.
Totally agree, nothing normal about that at all. The disc may not yet be dead but that pad's close to giving up and I suspect the two are related. If it was my car I'd be getting ready for a set of discs and pads. No point putting new pads on that old disc. If the car still has adequate braking and stops in a straight there may be no immediate rush so long as you keep an eye on things. I'd start by taking the car somewhere quiet and braking all the way to anti-lock. See what happens.
TTmonkey said:
It’s all a trick of the light (or lack of it) and the angles seen from the perspective of the camera.
Possibly - if the metal backing plate is a significantly different shape from the friction material. If the pad's even thickness all the way across then those brakes aren't too bad at all. Not perfect, but not bad at all.Maybe it is a trick of the light/shadow, but it looks like that outer pad might have been fitted badly from day one and has worn flat to the disc but wedge shaped, or as said there could be something wrong caliper wise.
If its been fitted badly from day on that could account for the ridge at the outer edge of the disc, because in its early stages of wearing down only a small but gradually increasing percentage of the friction material would have been in contact with the disc with the disc getting very hot at that point.
Less extreme but its why you get poor braking for a while when fitting new pads to badly worn discs, it takes a while for the pad to wear to the mishape of the disc, and something you can't rush due to excessive heat generated at the points of contact.
Be interesting to see the update to this thread, hopefully its just the picture and shadow angle giving a distorted view.
If its been fitted badly from day on that could account for the ridge at the outer edge of the disc, because in its early stages of wearing down only a small but gradually increasing percentage of the friction material would have been in contact with the disc with the disc getting very hot at that point.
Less extreme but its why you get poor braking for a while when fitting new pads to badly worn discs, it takes a while for the pad to wear to the mishape of the disc, and something you can't rush due to excessive heat generated at the points of contact.
Be interesting to see the update to this thread, hopefully its just the picture and shadow angle giving a distorted view.
Maxdecel said:
geeks said:
Could just be me or the angle of the photo but why is the pad a triangle shape?]
It's a chamfer used to prevent noise.I've seen much worse scoring recently on a 6 month old Qashqai e-power, I think caused by poor (largely non-existent) bedding in due to use of one pedal driving mode during a salty Scottish winter.
Probably not an issue on an M3.
If the braking is fine then there's probably nothing to worry about, but if the brakes have not been checked for some time I'd pull the calipers/pads and check for free movement of the slider pins and pads within the carriers and also check that the discs have not reached minimum thickness.
5s Alive said:
Max is correct, I don't think there's anything wrong with that pad.
I've seen much worse scoring recently on a 6 month old Qashqai e-power, I think caused by poor (largely non-existent) bedding in due to use of one pedal driving mode during a salty Scottish winter.
Probably not an issue on an M3.
If the braking is fine then there's probably nothing to worry about, but if the brakes have not been checked for some time I'd pull the calipers/pads and check for free movement of the slider pins and pads within the carriers and also check that the discs have not reached minimum thickness.
I've seen much worse scoring recently on a 6 month old Qashqai e-power, I think caused by poor (largely non-existent) bedding in due to use of one pedal driving mode during a salty Scottish winter.
Probably not an issue on an M3.
If the braking is fine then there's probably nothing to worry about, but if the brakes have not been checked for some time I'd pull the calipers/pads and check for free movement of the slider pins and pads within the carriers and also check that the discs have not reached minimum thickness.
Just to avoid any doubt.
Best comment on OP's question - Reckon it's a score created by material residue built up in the cross drilled hole, if you look it initiates at the top left of the hole and follows the rubbing path.
It's difficult to see but the score doesn't appear to complete a full rotation indicating to me the deposit self destructed at the end of the damage, suggests the dust collected in the hole probably got wet, swelled then hardened. It then became trapped between the pad and disc causing the score on the first application probably after been parked.
Cross drilled discs are known for clogging up on road cars, 911 Turbos were my first experience of them; 330 holes pr. disc drilled out on every major service
That was fun.OP - As long as the discs are within spec & there's no judder there's nowt to concern yourself with, just look out for hairline cracks starting around the holes. Drilled discs have a tendency in my experience.
Edit - Like this
Edited by Maxdecel on Monday 12th February 23:16
Wow, thanks for all the comments. I haven’t driven it since posting, but can confirm the pad on the other side is exactly the same (wedge shape) and also has the outer edge wear on the disc too. All rather bizarre.
I’ll pop the wheel off later this week and get a proper look and post pics of both sides! I’m fastidious when it comes to maintenance that I’m aware off, it went into BMW for a service a few months ago and they didn’t mention anything, but more than happy to change discs and pads if they need doing!
I’ll pop the wheel off later this week and get a proper look and post pics of both sides! I’m fastidious when it comes to maintenance that I’m aware off, it went into BMW for a service a few months ago and they didn’t mention anything, but more than happy to change discs and pads if they need doing!
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