C43 facelift: Unusual front disk wear pattern

[Jimjordan]

Looks like the discs are starting to clean up if you zoom in on the disc picture , possibly the car has been sitting for ages without moving and now that it is the holes on the discs are being clogged up with the residue corrosion.

Being that the calipers are solid and the pads are one piece then it would need to be some weird mechanical issue to cause the wear pattern yours are showing.

If there is plenty of `meat` on the discs then you could get them cleaned up and fit new pads.

How many miles have you done since picking up the car ?

K

Done about 110 miles (90 of those was motorway driving, bringing it home from where we bought it). Don't mind replacing the front pads/discs (27k on them already - dont see any replacements in the service history), just keen to make sure whatever happened to the current set doesn't just muller the new ones as well.

 

[Jimjordan]

OP = original poster, ie you.

Ah . I'll gladly share the outcome of this.

 

[grober]

looks like a multipiston caliper 6 ? and that pattern might arise if a couple of the pistons were jammed or mabe the wrong size of pads fitted?

 

[KennyN]

Done about 110 miles (90 of those was motorway driving, bringing it home from where we bought it). Don't mind replacing the front pads/discs (27k on them already - dont see any replacements in the service history), just keen to make sure whatever happened to the current set doesn't just muller the new ones as well.

Have you tried some "proper" braking ?

Cant think of any logical mechanical reason that you would have that particular wear pattern on the discs , exactly the same on both sides ??

Even if there was a sticking piston the other piston(s) would still push the pad squarely onto the disc.

K

 

[Jimjordan]

Have you tried some "proper" braking ?

Cant think of any logical mechanical reason that you would have that particular wear pattern on the discs , exactly the same on both sides ??

Even if there was a sticking piston the other piston(s) would still push the pad squarely onto the disc.

K

I did a couple of pretty hard 70+mph down to 20 on the day I got it to check for shudder etc (had warped disks once on a previous car). Didn't notice anything odd, shaved speed off quickly enough.

Not keen on pushing it now that it looks like it's using less than half of the pad friction surface on both front wheels.

I think I'll have to wait till I can get it to a local Merc mechanic next week to continue the investigation. The one consensus is that that wear pattern ain't right

Many thanks all for the feedback, comments and links! I'll share what we uncover...

 

[Bellow]

Looks like the disk face is absolutely clogged up with crap - the surface looks far too rough. the vent holes are clogged up too.
Interesting - would love to hear the outcome.

Agreed - a good clean up required.

Looks like the discs are starting to clean up if you zoom in on the disc picture , possibly the car has been sitting for ages without moving and now that it is the holes on the discs are being clogged up with the residue corrosion.

Agreed - a good clean up required.

Being that the calipers are solid and the pads are one piece then it would need to be some weird mechanical issue to cause the wear pattern yours are showing.

Odd though that there is both an outer and inner band making contact.

If there is plenty of `meat` on the discs then you could get them cleaned up and fit new pads.

A good manual clean and from there there's a fighting chance of reviving what's there. At least for long enough to ascertain the problem has gone.

 

[grober]

Brembo pads may also be directional

 

[grober]

How to fit and replace directional brake pads - Brembo

Before fitting Brembo directional brake pads, check the assembly instructions.

www.bremboparts.com

 

[Jimjordan]

You might be on to something with the directional pads.

The pads are not symmetricalThere is daylight visible between the ruler and the pad in the middle to the pad wear matches the wear pattern on the disk.

Had the disks (already lipped) and pads replaced now so I’ll keep an eye on them (garage found no other issues with the callipers when they put the new ones on)

 

[Bellow]

You might be on to something with the directional pads.

The pads are not symmetricalView attachment 122540There is daylight visible between the ruler and the pad in the middle to the pad wear matches the wear pattern on the disk.

Had the disks (already lipped) and pads replaced now so I’ll keep an eye on them (garage found no other issues with the callipers when they put the new ones on)

Out of interest, when you do the same on the reverse side (across the steel backing plate) is it correspondingly bowed?

 

[Jimjordan]

Out of interest, when you do the same on the reverse side (across the steel backing plate) is it correspondingly bowed?

Reverse side of the pad looks completely flat