CSL disc disintegrating??

Z

z4mcc

Member
Hi All,

has anyone seen an issue like this on their e46 m3 csl / z4m discs?

7-B58-CD3-A-4-A5-F-4-D4-A-BE01-4-CBDF00183-E9.jpg

it looks like the face is disintegrating. I thought the dull spots we’re pad build up but it’s actually indentation.

I can’t see any min thickness stamped into the discs so I wonder if this are non bmw part discs.
 
Not seen that sort of wear on any my discs. Surface corrosion, pitting, micro-cracks, pad transfer, yes, but nothing like that.

The closest I've ever see to that was when an acquaintance decided to spruce up his e34 M5's discs by getting them chrome-plated - and wondered why braking performance had gone off a cliff :P :headbang:

Part number & min thickness should be on the shoulder of the bell/hat.

320050_x800.jpg

Part numbers should be 2282446 for RHS and 2282445 for LHS.
 
That's not the discs, it looks like pad backing to me. You got any pads left?
 
Loads of pad left yes. The lack of part numbers and stamping is very suspicious.

Is it still cotswolds for best price on new discs. Thruxton is next and it would be nice to have brakes :)
 
z4mcc said:
Loads of pad left yes. The lack of part numbers and stamping is very suspicious.

Is it still cotswolds for best price on new discs. Thruxton is next and it would be nice to have brakes :)
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Cotswolds stopped being the cheapest a while ago.

I find Rybrook Warwick, Harry Fairbairn and Douglas Park Hamilton to be cheaper.

Having said that, I got a quote for new discs and pads for circa £512 from main dealer. Yet fitted at main dealer was £520...so in the end I ended up paying the extra £8 for them to be fitted...
 
z4mcc said:
Loads of pad left yes. The lack of part numbers and stamping is very suspicious.

Is it still cotswolds for best price on new discs. Thruxton is next and it would be nice to have brakes :)
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Those discs have barely covered a couple of thousand miles , why would you replace them if they still function :?
 
z4mcc said:
Loads of pad left yes. The lack of part numbers and stamping is very suspicious.

Is it still cotswolds for best price on new discs. Thruxton is next and it would be nice to have brakes :)
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Part numbers on the discs or pads?

They've got too hot either way, what pads are you using?

Discs should clean up as mr wilks says :thumbsup:
 
Huge brake judder when hot. Rc6 pads.

Might be worth giving them a skim.

They are 27.8mm so plenty of thickness left.

It won’t clean up as it’s not deposits. It’ll need to ware down.
 
Something wrong with the metal those have been made from, pads should have produced a smooth surface over the face of the disc, are both sides showing up the same condition? You could try having them skimmed and see if it returns, if it comes back then I would change them for a reputable brand with new pads.
 
I'm always on the look out for consumables and I've noticed that disc prices have gone up a lot lately, I'm sure c£250 would get you a pair of fronts not too long ago!
 
Very odd. I wonder if they built up an uneven layer of rust at some point and were then “etched” by subsequent usage?

Skimming would get my vote.
 
z4mcc said:
Huge brake judder when hot. Rc6 pads.

Might be worth giving them a skim.

They are 27.8mm so plenty of thickness left.

It won’t clean up as it’s not deposits. It’ll need to ware down.
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Just had a quick Google, not fully upto speed on CL pads, from the specs they sound very harsh, oem discs have never been designed to run at them sort of temperatures.

I think a skim is the way forward, it'll just happen again with them pads though unless you manage to improve the cooling?
 
Seems like pretty straightforward galling caused by using a stainless steel disc and aggressive (their words) incomparable pad..

https://www.bssa.org.uk/topics.php?article=12 Refers
 
I’ve ran rc5/6 on various cars including m cars without issue.

I’ve ordered some proper bmw discs from cotswolds (cheapest in the end) and will see how they hold up.
 
Stainless steel materials gall very easily....common problem with stainless steel nuts n bolts with threads damaging..

One of the main reasons most discs are made of high grade cast iron..
 
Pbondar said:
Seems like pretty straightforward galling caused by using a stainless steel disc and aggressive (their words) incomparable pad..

https://www.bssa.org.uk/topics.php?article=12 Refers
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I've never heard of car brake discs being made of stainless steel. If they are, they are certainly not up to the job.

I think they are just poor quality discs.
 
Lower said:
Pbondar said:
Seems like pretty straightforward galling caused by using a stainless steel disc and aggressive (their words) incomparable pad..

https://www.bssa.org.uk/topics.php?article=12 Refers
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I've never heard of car brake discs being made of stainless steel. If they are, they are certainly not up to the job.

I think they are just poor quality discs.
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If you look at the picture, it doesn't seem to me to be the usual cast iron disc..lack of corrosion seems to indicate a different materal?
 
Pbondar said:
Seems like pretty straightforward galling caused by using a stainless steel disc and aggressive (their words) incomparable pad..

https://www.bssa.org.uk/topics.php?article=12 Refers
Click to expand...
Tend to agree with this prognosis. Though I didn't realise you could get stainless discs for the Z4 before I saw this. :?

Looks like plenty left in them so a skim would recover the surface.

Then softer pads for normal road use.

But if they are stainless, then heavy road / track work is going to do the same thing again. :(
 
z4mcc said:
I’ve ran rc5/6 on various cars including m cars without issue.

I’ve ordered some proper bmw discs from cotswolds (cheapest in the end) and will see how they hold up.
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If you don't change the pads change the cooling setup, have you the ducts in the bumper open?

Some oem discs (if yours aren't oem? ) could be better quality but they will still get to roughly the same temperature as your current discs assuming they are similar mass and design.

You either need bigger thicker discs that can take more heat or more cooling or different pads or all three :thumbsup: :driving:
 
I don’t think this is a consequence of overheating. I ran OEM discs on my car for about eight years, during which I covered thousands of miles on track using progressively more aggressive brake pads with each pad change. On numerous occasions I’ve seen pads smoking even after cool down laps and I’ve even had the friction surface of the pads break up through over heating. I’ve also seen OEM discs crack from heat stress (albeit not mine). However, I’ve never seen a disc that looks like that.
I suspect these discs are cheap copies of the OEM discs and they are not fit for purpose. The pad choice is probably irrelevant.
 
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