Has anyone else's Leon Cupra started to suffer from the rear discs turning black

[RUM4MO]

My oldest daughter's May 2019 Leon Cupra has only done 10K miles from new, but now I see that the rear discs are black with corrosion and badly ridged - is this what any other people are finding probably due to lack of continuous use?

I scanned her car on Sunday prior to it getting its second service today and checked the discs then, initially I thought that the driver's side rear disc had turned blue or bluesih as she has just returned from a trip down to Canterbury (and back up to Edinburgh). She later confirmed that neither side gets warm or hot when the car is being driven around, so I worried less as initially I thought that it was due to the rear brakes partially seizing/dragging.

I'd think that I'll be suggesting that they get replaced before its first MOT and probably I'll fit Pagid discs and probably Pagid pads on the rear. The front discs are perfect so no worries at that end.

In the past I've found that any replacement discs stay in good condition longer than the original factory fitted ones, well from VW at least.

Finally, yes I know if you look at cars in any car park, the rear discs probably don't look to be in good condition, lots of that will be due to most cars not needing to hand over very much of the braking effort to the rear discs, so they don't suffer much from wear which equals they do suffer more from corrosion!

Edit:- by the way, my 2011 Audi S4 at (gulp!) 24.5K miles, has nice shiny front and rear discs, my wife's 2015 VW Polo 1.2TSI 110PS at 34.5K miles, has nice shiny front discs but the rear ones are slightly marked with corrosion.

 

[Woody_72]

Is the car an automatic by any chance? If people don't use the handbrake, the whole mechanism corrodes and the pivoting arm seizes and the caliper stops working properly. When I got mine, the rear discs were in a shocking state and the whole mechanism barely moved. I replaced the discs and pads and used the handbrake properly (it took a lot of pulling it on HARD before the whole mechanism freed up) and now the new discs and pads are wearing normally and the mechanism has freed up perfectly.

Link here so you can see what I'm referring to.

 

[DigitalSushi]

Not black but certainly i get surface rust on them, that's normal. Blue disks yeh is almost certainly overheating and the fact that they are lipped and ridged would indicate at some point something was binding heavily but may have released now, when you say ridged is that on the disc surface (ie the bit the pads squeeze to).

After 10k miles they really should not be looking dodgy at all, mines at 35k with nothing like that on the discs and that includes a lot of exuberant/dumb use.

Bit hard to guess without some pics but honestly if I saw this on my daughters car then yes i would be looking at replacing both discs and pads with a decent garage who will give the callipers a good service to ensure they dont bind. Fast car with possibly dodgy brakes

 

[RUM4MO]

Is the car an automatic by any chance? If people don't use the handbrake, the whole mechanism corrodes and the pivoting arm seizes and the caliper stops working properly. When I got mine, the rear discs were in a shocking state and the whole mechanism barely moved. I replaced the discs and pads and used the handbrake properly (it took a lot of pulling it on HARD before the whole mechanism freed up) and now the new discs and pads are wearing normally and the mechanism has freed up perfectly.

Link here so you can see what I'm referring to.

Yes it is an DSG, as are all later Cupras and no not that issue as it has an electric handbrake. This car does not have any grabbing or seizing coming from these rear brakes everything run free, but it progressively turned black on the driver's side due to corrosion.

 

[RUM4MO]

Not black but certainly i get surface rust on them, that's normal. Blue disks yeh is almost certainly overheating and the fact that they are lipped and ridged would indicate at some point something was binding heavily but may have released now, when you say ridged is that on the disc surface (ie the bit the pads squeeze to).

After 10k miles they really should not be looking dodgy at all, mines at 35k with nothing like that on the discs and that includes a lot of exuberant/dumb use.

Bit hard to guess without some pics but honestly if I saw this on my daughters car then yes i would be looking at replacing both discs and pads with a decent garage who will give the callipers a good service to ensure they dont bind. Fast car with possibly dodgy brakes

The car has just come back from a service with no comments which makes me think that they are seeing a lot of this!

It will be me that replaces these discs and pads when the time comes, I'd hazard a guess that the braking effort from these nasty discs will exceed the MOT requirements and these electric handbrakes grab these discs with a lot more effort than a simple wire cable handbrake could ever dream about.

There is actually no blueing, I initially "saw" what I thought was slight blueing but after having another look it is just polished black, the ridges or more correctly radial grooves are what many people will get seeing appearing on their rear at least VW Group cars, discs, that sort of "behaviour" concerned my mate with his May 2018 T-Roc 150PS - but he traded it in so that no longer concerns him - for now!

I'm still looking for more comments as I think that there must be quite a few low use cars ending up with this issue. When it comes, my fix will be to use quality aftermarket discs and pads, no more VW Group brake spares for me, I never have bought brake parts from VW Group, this issue will probably disappear with no non VW Group discs and pads.

 

[Big Col]

I've never had to replace rear discs or pads on any car due to them wearing out - its always due to corrosion.

On my Leon the inside pad seized in the carrier on both sides. On my Golf - bought at 3 year old - it failed its first MOT on the rear brakes, thats how bad it was. It had brand new discs and pads when I bought it. Similar stories on my Ibiza and Fabia.

I do 20K miles a year and give the brakes a good 'italian tune up' when I can and they still suffer. The rust on the unswept area of the discs grows into the swept area.

I guess the rear brakes just dont work hard enough to keep them clean like the fronts.

 

[RUM4MO]

Last time I needed to replace a brake disc because it was worn, was on a 1994 Ford Fiesta 1.6SI, back then "British" cars, my case Fords always used 2 or 3 sets of pads before the discs were due to be changed. We had just come back from being away on holiday, and I left my car and used my wife's Ford Fiesta really to make sure it was ready for use after its rest. Braking below 30MPH was okay, braking above that resulted in a serious vibration - reason being one front disc had weakened so much that the disc was cracking at a weak point at the "top hat" section, I sorted that ome right away and made sure that that never ever caught me out again, my mistake!
Nowadays, if a disc lasts 2 sets of pads that is good enough for me, except corrosion has always beat me to that point with especially rear VW Group cars original discs.

Edit:- pads on the other hand, I tend to replace when they are over 2/3 worn so never ever letting them get down to the maybe MOT limit of 2mm, doing that is crazy.

 

[Mr Pig]

I think the lockdown has done a lot of damage to cars. My son was working from home so his car hardly moved. He keeps it in a garage too which doesn't help. The underside of his car is a lot more rusted than it should be for its age and his brake disks are wrecked.

The calipers can seize, disks rust up. If the disks rust badly enough it doesn't clean off, just gets polished and burned by the pads. Basically, free everything off, new pads and disks and drive the car. All should be well.

 

[Cuprabenwytm]

Do some 60 to 0 soon free em. Up lol

Sent from my MRD-LX1 using Tapatalk

 

[SuperV8]

The car has just come back from a service with no comments which makes me think that they are seeing a lot of this!

It will be me that replaces these discs and pads when the time comes, I'd hazard a guess that the braking effort from these nasty discs will exceed the MOT requirements and these electric handbrakes grab these discs with a lot more effort than a simple wire cable handbrake could ever dream about.

There is actually no blueing, I initially "saw" what I thought was slight blueing but after having another look it is just polished black, the ridges or more correctly radial grooves are what many people will get seeing appearing on their rear at least VW Group cars, discs, that sort of "behaviour" concerned my mate with his May 2018 T-Roc 150PS - but he traded it in so that no longer concerns him - for now!

I'm still looking for more comments as I think that there must be quite a few low use cars ending up with this issue. When it comes, my fix will be to use quality aftermarket discs and pads, no more VW Group brake spares for me, I never have bought brake parts from VW Group, this issue will probably disappear with no non VW Group discs and pads.

The problem is not your genuine discs and pads - the problem is lack of use, and maybe caliper sticking somewhere, also your location - if you are near the coast for example. This can effect ANY car brand.

VW don't make brake discs and pads or brake systems for that matter, there are a handful of big braking suppliers in Europe which supply most of the European auto industry, same for Asian vehicles.

Don't think that because you see TRW, Bosch or Continental on an OEM brake pad that they actually make the OEM pads - just marketing. If you look carefully you will see a small name like Textar/Galfa/Ferrodo/Brembo etc - and again don't think that TRW, Bosch, Continental, Textar, Galfa, Ferrodo, Brembo etc.. aftermarket pads are the same as the OE pads are the same because they are NOT.

It used to be the case 20+ years ago that rear brakes saw a lot less heat than the fronts, but for modern brake systems the rears can see equal if not more heat than the fronts. Yes they do less work - due to weight transfer to the front axle whilst braking, but they are sized accordingly smaller to they have less thermal mass.

Brakes need to see some heat from time to time which keeps them in good condition - which unfortunately is at odds with eco driving and avoiding/feathering the brake pedal.

 

[RUM4MO]

I think that you will find that I’ve covered all that matters in my opening posting, including “lack of work being handed over to the rear brakes”, truth is, whenever I’ve moved to another disc supplier I’ve solved that problem for much longer. I’ve never fallen for the “OEM supplier” where it means that a certain manufacturer is selling new friction parts and they only ever have got contracts to supply maybe fuel filters.

In the “good old days” when brake discs cost a lot of money, it was cost effective to get discs dressed, but not now - the fix is to replace discs and pads. I always do my own brake work so probably I’ll need to work on my older daughter to cough up for the parts.

Edit:- in my experience Textar and Pagid who have been factory suppliers for brake pads or suppliers to TRW who supply some of these complete packages, do list an “as factory” replacement kit it is just ECP that that tend to sell only a shortened range of Textat/Pagid kits, I have had a discussion with the UK tech/marketing team over ECP being the sole importer of these parts and not doing/providing what is need, in each case I was supplied with exactly the correct kit, and I’ll repeat that action every time ECP do not supply the exact correct kit.

 

[SuperV8]

ECP I believe has a licencing agreement to use the Pagid name. Quite different product & quality compared the OE and probably not even made in the same factory.
Assuming the Leon has 272x10 rear discs and an 'ATE' caliper then this is the OE pad:
5Q0698451Q
ATE brake system - Pagid friction material code PA4357

Pagid aftermarket pad - Friction material code PA4016 (this is a general aftermarket material used across many of their rear pads)
Ignore the EE suffix, this is just the AMECA code used in the US and is rather meaningless, EE being a lower friction coefficient hot and cold.

This OE pad also uses a fine-blanked back plate vs conventional blanking for the Pagid aftermarket (as well as most other aftermarket).

The car is still quite new - you might be ok just taking apart/inspecting/cleaning the original brakes (slide pins/pad abutment points/piston) - and then performing a bedding cycle to try to clean up the discs, depends on how bad they are?

 

[RUM4MO]

Yes, unfortunately I've heard that about Pagid, not really very useful for DIYers wanting to buy good service parts - okay if Pagid's "true quality" parts were also available from another source, then ECP's offerings could be avoided, but I'm not sure if any other motor factors supply "true quality" Pagid parts.

Could you explain the differences between OEM and Pagid from ECP's backing plate? I know ECP tend to sell a "compressed" range of Pagid etc range of brake parts, I've even bought ATE for the rear brakes on my old 2000 VW Passat 4Motion which would have had Girling/Lucas rear callipers - and the ATE offering had no tapered shim on the backing plate - so braking for a couple of weeks was as "loud as a taxi" - after that I bought Pagid or Textar whichever VW had fitted at factory and they had tapered shims like the factory fitted ones and no more noises.

I seem to remember that the factory fitted pads on the front of my wife's 2015 Polo have VW Group p/n + TRW p/n + Jurid on them. It is easy to see why, TRW will have had the supply contract for braking assemblies to factory so have their branding on them, they will have sourced the pads from Jurid and everything needs the VW Group p/n.

Cleaning up these discs, at one time I seem to remember that you could buy pads that had a sacrificial sheet of abrasive that could be used to "dress" slightly tarnished/rusted discs, these sheets just wore away and then it was back to normal friction material. I have considered removing both discs and trying to use a rotary wire brush on both faces of both discs - but my daughter and her partner probably are not interested in me taking that action and then wanting to replace these discs. I've seen pictures of newish discs that have ended up with sections of the top surface falling off, or ripped off by the pads after slight corrosion had set in - I've personally never had that happen.

Bottom line is, that daughter's partner is a car guy, well Lotuses - or now just one Esprite, and I'll bet that car would never have even the slightest mark on its brake discs - but it is seen as a proper car, the 2019 Leon Cupra is seen as a boring modern runabout maybe not worthy of such attention to detail!!

Edit:- I found it very easy to be concerned about what I first spotted on these discs considering the car is a May 2019 reg'd car with very little miles under its belt - but how deep this corrosion/blacking is, I can't say, if it was my car I would have done something about before it got this bad. The rear discs on my 2011 Audi S4, which were replaced all round under warranty it seems due to vibration, so still VW Group parts, but not factory fitted ones, are still spotless after 14K miles being put on these pads, it has manual trans and HillHold is not always enabled - by default on older cars like that it is OFF.

 

[SuperV8]

Yes, unfortunately I've heard that about Pagid, not really very useful for DIYers wanting to buy good service parts - okay if Pagid's "true quality" parts were also available from another source, then ECP's offerings could be avoided, but I'm not sure if any other motor factors supply "true quality" Pagid parts.

Could you explain the differences between OEM and Pagid from ECP's backing plate? I know ECP tend to sell a "compressed" range of Pagid etc range of brake parts, I've even bought ATE for the rear brakes on my old 2000 VW Passat 4Motion which would have had Girling/Lucas rear callipers - and the ATE offering had no tapered shim on the backing plate - so braking for a couple of weeks was as "loud as a taxi" - after that I bought Pagid or Textar whichever VW had fitted at factory and they had tapered shims like the factory fitted ones and no more noises.

I seem to remember that the factory fitted pads on the front of my wife's 2015 Polo have VW Group p/n + TRW p/n + Jurid on them. It is easy to see why, TRW will have had the supply contract for braking assemblies to factory so have their branding on them, they will have sourced the pads from Jurid and everything needs the VW Group p/n.

Cleaning up these discs, at one time I seem to remember that you could buy pads that had a sacrificial sheet of abrasive that could be used to "dress" slightly tarnished/rusted discs, these sheets just wore away and then it was back to normal friction material. I have considered removing both discs and trying to use a rotary wire brush on both faces of both discs - but my daughter and her partner probably are not interested in me taking that action and then wanting to replace these discs. I've seen pictures of newish discs that have ended up with sections of the top surface falling off, or ripped off by the pads after slight corrosion had set in - I've personally never had that happen.

Bottom line is, that daughter's partner is a car guy, well Lotuses - or now just one Esprite, and I'll bet that car would never have even the slightest mark on its brake discs - but it is seen as a proper car, the 2019 Leon Cupra is seen as a boring modern runabout maybe not worthy of such attention to detail!!

Edit:- I found it very easy to be concerned about what I first spotted on these discs considering the car is a May 2019 reg'd car with very little miles under its belt - but how deep this corrosion/blacking is, I can't say, if it was my car I would have done something about before it got this bad. The rear discs on my 2011 Audi S4, which were replaced all round under warranty it seems due to vibration, so still VW Group parts, but not factory fitted ones, are still spotless after 14K miles being put on these pads, it has manual trans and HillHold is not always enabled - by default on older cars like that it is OFF.

RUM4MO;
Regarding backing plates:
This VAG OEM & most OEM pads use a fine blanked steel back plate - which is a more precise blanking process which can hold tighter tolerances and give a better, flatter finish.
Most aftermarket pads - including this one - just use conventional blanking - think like pressing out a cookie cutter in pastry - not as precise or as good finish.
The trouble is that fine blanking tooling is very expensive so you have to have high volume to amortise the tooling cost - fine for OEM where you are churning out high volumes of one part number - BUT in the aftermarket where you have lower volumes and more variety this is a problem.

Regarding friction materials - these really are a secret sauce:
OEM's have hundreds of different friction materials - each one 'tailored' to that manufactures individual requirements following years of testing.
Aftermarket have a handful of different materials to pick from - the better ones have more materials (more than 10) to better match the original material - the 'not so good' ones have 2 (front and rear) or even 1 to cover 1000+ parts!

Regarding anti-noise shims:
OEM's have thousands of variations to pick from following years of testing each with varying composite construction using differing steel, stainless steel, rubber and adhesive combinations.
Aftermarket can have none, rubber coat(paint), or just plain metal (painted). I would avoid these, you really want a good shim.

Unfortunately you don't always get what you pay for with brakes - often you are paying for a big name and not much else. Yes, most will be fine for pottering around, but I have carried out brake tests (part of my automotive engineering job) where the braking after several high speed stops really faded to the point where when the OEM and 1x aftermarket had stopped - the vehicle with a couple of the big name pads was still doing 50+mph!

Yes, that abrasive sheet to 'dress' the discs is no longer a 'thing' Brake discs are machined and required to be ever increasing tolerances (less than 0.010mm thickness variation - 10 microns!) that any disc/pads issues generally just require new discs.

I wouldn't rotary brush the discs -just try re-bedding in process. Something like:
Find a quiet stretch of road and do 10 stops, from 60mph - 20mph at about 50% effort (100% being an ABS stop) most IMPORTANT while doing this is not to come to a complete stop with your foot on the brake.

 

[RUM4MO]

@SuperV8 , thanks for clearing that up wrt brake pad backing plates.

Just one other thing, how are brake discs manufactured, are they drop forged?

The reason that I ask is that I've seen more than 2 incidences - ie pictures, of front discs having "delaminated" and so causing issues, these were on all on Polo/Ibiza/Fabia, and were all original factory fitted discs. sectors of the shiny silver surface had vanished revealing a darker - I'd think corroded under surface.

Now some people were just thinking that discs are not "one part/material" and that they are made up from some inferior internal bulk of slightly junk metal and coated with higher quality metal to form the friction surface.

That did not seem correct to me but I did not bother commentating on it as I'd, at that time never come across problems with discs.

Now that I've seen other non family cars with nasty looking dark finishes on mainly rear discs, and now the same on my daughter's Leon Cupra rear discs, I've started to consider that maybe on her car this darkening is due to some form of separation caused possibly by "material pour interruption" during disc manufacture, ie material laminating.

I can't see me leaving this problem alone though it seems to be an uphill battle suggesting I'll provide the labour/effort if she or her partner provide quality new parts as it simply is not a problem right now, backed by a dealership (but not the SEAT branch) not commenting on it at service time. The only reason that that car did not get worked on by the SEAT dealership seems to have been down to, during the online booking process made directly on the dealership's SEAT area of the website, after inputting all the car's details and her details, "a new improved service feature" directed her to dropping the car off at a much nearer site of that dealership, seemed like a good idea to her as up to this time everything was standard SEAT UK chat wrt servicing. I asked if she did not mind her car being ragged across town to the SEAT dealership and back, but she had not considered that. Anyway, at the point of dropping the keys off, she was asked if there was any other work she wanted them to carry out and she mentioned the usual CarPlay issues which seem to be a common "thing" at least across the VW Group fleet - their answer was "we are not a SEAT dealership so we can't investigate that" - so that car was doomed to get a quick prepaid for oil and filter change and nothing more, no INSPECTION part of year 2 service or much more - other than 2 offers to use GOOD or EXCELLANT flusher additive prior to the oil change, ie first offering was cheaper than the second offering - I suggested that she decline both, strange to me that they offered the cheaper option first, but there you are.

 

[Woody_72]

Discs aren't forged, pretty sure they're sand cast (you can see this by looking at the area around the fins) and then machined to tolerance.

 

[SuperV8]

@SuperV8 , thanks for clearing that up wrt brake pad backing plates.

Just one other thing, how are brake discs manufactured, are they drop forged?

The reason that I ask is that I've seen more than 2 incidences - ie pictures, of front discs having "delaminated" and so causing issues, these were on all on Polo/Ibiza/Fabia, and were all original factory fitted discs. sectors of the shiny silver surface had vanished revealing a darker - I'd think corroded under surface.

Now some people were just thinking that discs are not "one part/material" and that they are made up from some inferior internal bulk of slightly junk metal and coated with higher quality metal to form the friction surface.

That did not seem correct to me but I did not bother commentating on it as I'd, at that time never come across problems with discs.

Now that I've seen other non family cars with nasty looking dark finishes on mainly rear discs, and now the same on my daughter's Leon Cupra rear discs, I've started to consider that maybe on her car this darkening is due to some form of separation caused possibly by "material pour interruption" during disc manufacture, ie material laminating.

I can't see me leaving this problem alone though it seems to be an uphill battle suggesting I'll provide the labour/effort if she or her partner provide quality new parts as it simply is not a problem right now, backed by a dealership (but not the SEAT branch) not commenting on it at service time. The only reason that that car did not get worked on by the SEAT dealership seems to have been down to, during the online booking process made directly on the dealership's SEAT area of the website, after inputting all the car's details and her details, "a new improved service feature" directed her to dropping the car off at a much nearer site of that dealership, seemed like a good idea to her as up to this time everything was standard SEAT UK chat wrt servicing. I asked if she did not mind her car being ragged across town to the SEAT dealership and back, but she had not considered that. Anyway, at the point of dropping the keys off, she was asked if there was any other work she wanted them to carry out and she mentioned the usual CarPlay issues which seem to be a common "thing" at least across the VW Group fleet - their answer was "we are not a SEAT dealership so we can't investigate that" - so that car was doomed to get a quick prepaid for oil and filter change and nothing more, no INSPECTION part of year 2 service or much more - other than 2 offers to use GOOD or EXCELLANT flusher additive prior to the oil change, ie first offering was cheaper than the second offering - I suggested that she decline both, strange to me that they offered the cheaper option first, but there you are.

No, automotive brake discs are cast iron.
Really bugs me on youtube videos when they talk about 'steel' discs
Again - the OEM will often use different iron grades alloyed with other metals, The aftermarket uses base cast iron, or high carbon which generally has better noise damping characteristics.

Can you share photos of these rear discs?

I have not personally heard/seen discs 'delaminating'

 

[RUM4MO]

Okay, I'll try to cross paths with that car soon and take some pictures.

I would never expect to find brake discs "delaminating" and personally have'nt - just seen pictures where it has been confirmed that a "layer" of top material had parted - over a sector of the swept area, from discs that were otherwise looking A1, ie still like new. That was why I had considered that the pouring process had possibly had suffered an interruption and allowed the bulk of the liquid metal to start setting before the final quantity had been added - not many other reasons why an object made form poured metal would end up "delaminating".