[JD6]

My dealer has let me know that my front discs have 1.5mm remaining and the rears 2mm. I'm interested to know what the total available wear is on these discs (blue M Sport) when new so I can understand what proportion worn they are?

I realise this has been discussed before, but I can't find it.

[lethbridge]

Not sure that makes sense? As far as I am aware the max permitted wear on the disc is 1.6mm front & rear. Someone correct me if I'm wrong...

Fronts (370mm) are 30mm and can wear down to 28.4mm
Rears (345mm) are 24mm and can wear down to 22.4mm

[JD6]

Originally Posted by lethbridge

Not sure that makes sense? As far as I am aware the max permitted wear on the disc is 1.6mm front & rear. Someone correct me if I'm wrong...

Fronts (370mm) are 30mm and can wear down to 28.4mm
Rears (345mm) are 24mm and can wear down to 22.4mm

Thanks.

That sounds strange. My rear discs appear to be thicker now than when the car was new 46k miles ago! If your figures are right, my dealer must have got their measurements wrong.

[JD6]

Actually there is some other stuff that sounds odd on the Vehicle Health Check. My front pads are showing 5mm remaining and rears 6mm remaining, and yet they are marked as 80% worn and 70% worn respectively. Both are in the amber section showing needs attention soon.

[teaston]

Originally Posted by JD6

Actually there is some other stuff that sounds odd on the Vehicle Health Check. My front pads are showing 5mm remaining and rears 6mm remaining, and yet they are marked as 80% worn and 70% worn respectively. Both are in the amber section showing needs attention soon.

I don't let pads go below 4mm, so those figures are about right.

[JD6]

Originally Posted by teaston

I don't let pads go below 4mm, so those figures are about right.

Cheers. As I tend to get the dealer to do all work, replacing pads probably costs me £200 a set I think - a fair bit more than it costs you, so I tend to replace later. Perhaps they are assuming replacement at 3mm.

Do you agree with the disc figures that lethbridge quoted?

[lethbridge]

A dealer will usually insist on replacing pads and discs. Their logic is reasonable - if you only replace the pads, the discs will have worn down to tolerance before the next set of pads would be due (and you have to fit new pads when you replace discs).

Whilst your fronts may need doing I'd be surprised if the rears do - they usually have quite a bit more wear in them - when you reset the warnings the rears get set to 80k miles and the fronts 47k. Not a remotely exact science though as your driving style will dictate this - I spend all my time on motorways and would normally expect to not need to replace until around 70-80k on fronts & 110-120k on rears...

[teaston]

Originally Posted by JD6

Cheers. As I tend to get the dealer to do all work, replacing pads probably costs me £200 a set I think - a fair bit more than it costs you, so I tend to replace later. Perhaps they are assuming replacement at 3mm.

Do you agree with the disc figures that lethbridge quoted?

Originally Posted by lethbridge

A dealer will usually insist on replacing pads and discs. Their logic is reasonable - if you only replace the pads, the discs will have worn down to tolerance before the next set of pads would be due (and you have to fit new pads when you replace discs).

Whilst your fronts may need doing I'd be surprised if the rears do - they usually have quite a bit more wear in them - when you reset the warnings the rears get set to 80k miles and the fronts 47k. Not a remotely exact science though as your driving style will dictate this - I spend all my time on motorways and would normally expect to not need to replace until around 70-80k on fronts & 110-120k on rears...

Conveniently I’ve always found these discs have worn by around 0.7-0.8mm after one set of pads have worn out, so perfect for two sets of pads per disc!

Some ‘stealers’ will still try to sell you new discs though obviously.

[JD6]

Originally Posted by lethbridge

A dealer will usually insist on replacing pads and discs. Their logic is reasonable - if you only replace the pads, the discs will have worn down to tolerance before the next set of pads would be due (and you have to fit new pads when you replace discs)..

Given that a set of blue M Sport discs are somewhere in the region of £6-700 a pair fitted, and brake pads are more like £200 a pair fitted (perhaps £150 if done with the discs), the logic doesn't seem so reasonable to me, unless the discs are needed pretty soon.

I'm not going to throw away say £250 worth of life left in the discs to save myself £150 in future.

[lethbridge]

Suspect their other reason may be around safety - the wear warning is the on the pad so there is nothing to warn you the disc has warn below tolerance if you change the pad and not the disc - I'm with you though, I just change what is needed but then that is an easy option if you DIY...

[teaston]

Originally Posted by lethbridge

Suspect their other reason may be around safety - the wear warning is the on the pad so there is nothing to warn you the disc has warn below tolerance if you change the pad and not the disc - I'm with you though, I just change what is needed but then that is an easy option if you DIY...

The disc wear limits are actually being over cautious, as long as you don’t break through this wear indicator on the edge of the disc then technically the brakes are safe: