That's cracked it

[WDB124066]

Brake discs (even good-quality ones) suffer a very-hard life.
They are constantly being heated-up and cooled down in a very short space of time - The heat distribution is often severe and uneven - The thinner they get, the more extreme is the thermal fatigue that they endure.
Perhaps we should be surprised that they don't crack more frequently.

Other real problem is that a very-large proportion of brake discs in use today originate in China (no matter what label they carry).
Some of them are utter rubbish.

I fitted a set of front discs to a Jeep Cherokee not too long ago.
They looked horrible when I took them out of the box.
So much so - That I ultrasonic tested and dye-pen tested them before fitting.
They were not obviously rejectable, but their surface was a variable colour - Which is not a good sign on machined castings.
I fitted them with usual care - New pads at the same time.
Twelve months (25k miles) later, the braking was lumpy.
The discs were clearly disintegrating.
I got my money back on the discs, but needed to fit a new set of pads at my expense.

This has got me thinking here quietly I might just get a tech to MPI my rotors after every 1/2 pad of wear or so. MB customers can't really dictate what is made where, so we may well end up with bits from places we really don't trust too much = pays to check.
A hardness test every now and then will tell a bit about rotors, both new and worn, I might have a play one day....

I've worked on projects and I am sure you have too johnsco where sourcing from certain Countries of origin is expressly written into contracts as forbidden, bit like Israel when working in Arabic Countries - it just does not exist.

 

[Lord-WYBMAnE220]

, but needed to fit a new set of pads at my expense.

You coulda just flatted them off by rubbing them on a sheet of 140 laid on a flat surface.

 

[Lord-WYBMAnE220]

This has got me thinking here quietly I might just get a tech to MPI my rotors after every 1/2 pad of wear or so. MB customers can't really dictate what is made where, so we may well end up with bits from places we really don't trust too much = pays to check.
A hardness test every now and then will tell a bit about rotors, both new and worn, I might have a play one day....

I've worked on projects and I am sure you have too johnsco where sourcing from certain Countries of origin is expressly written into contracts as forbidden, bit like Israel when working in Arabic Countries - it just does not exist.

Nothing to stop you supplying your own genuine parts. I'm lucky in living close to Camberley AutoFactors who supply many OEM parts (identical to the stealership item) for things like wheelbearings, etc at 1/3rd the price.
Example : Couple of years ago, bought a non-OEM bearing for my Volvo S80, from a reputable local autofactor - but it set off the skid alert (or similar, can't quite remember).
So went and got the genuine article (duly compared with the dealership's) from CAF and buddaboom! - dash warning disappeared.
For some (semi-regular) items, it's worth buying the dealership part just to compare to the OEM part procured elsewhere (and obviously, then taking it back).

 

[kth286]

Nothing to stop you supplying your own genuine parts. I'm lucky in living close to Camberley AutoFactors who supply many OEM parts (identical to the stealership item) for things like wheelbearings, etc at 1/3rd the price.
Example : Couple of years ago, bought a non-OEM bearing for my Volvo S80, from a reputable local autofactor - but it set off the skid alert (or similar, can't quite remember).
So went and got the genuine article (duly compared with the dealership's) from CAF and buddaboom! - dash warning disappeared.
For some (semi-regular) items, it's worth buying the dealership part just to compare to the OEM part procured elsewhere (and obviously, then taking it back).

and paying the returns surcharge ?

might as well have purchased the original dealer part at the outset.

 

[kth286]

Be assured; the Mercedes operation will be testing that components made under contract, and packed in their own boxes with the hologram, DO meet full specs as laid down themselves.

Wow betide any contract manufacturer not complying.

There have been countless times that Mercedes have taken businesses to court over copy parts - the big one was copy wheels in past years.

 

[Lord-WYBMAnE220]

and paying the returns surcharge ?

Only if it's returned after the specified 2 or 4 weeks.
Varies by dealership.

 

[Lord-WYBMAnE220]

Be assured; the Mercedes operation will be testing that components made under contract, and packed in their own boxes with the hologram, DO meet full specs as laid down themselves.

Wow betide any contract manufacturer not complying.

There have been countless times that Mercedes have taken businesses to court over copy parts - the big one was copy wheels in past years.

Are you talking about two different things here ?
Their own gen-MB parts manufactured by their contracted suppliers - and unconnected manufacturers selling knock-offs as genuine Mercedes parts ?

 

[kth286]

Are you talking about two different things here ?
Their own gen-MB parts manufactured by their contracted suppliers - and unconnected manufacturers selling knock-offs as genuine Mercedes parts ?

It was suggested in above posts that the original parts purchased via Mercedes had become faulty; and subsequent suggestions reasoned it was because they were made in China.

I was merely pointing out that Mercedes have a strong follow up process of checking products made by contractors meet 'the design spec'.

The manufacturers could be any business that Mercedes have contracted with for that particular part.

So, I am suggesting have no fear with original Mercedes parts - they will meet the design spec.

The thinking so many persons have is that just because a business that manufacturers original Mercedes parts also supplies 'other' copy parts suitable for Mercedes, it is identical. It will not be identical, whilst being made during the contract period.

 

[johnsco]

I am sure that MB are very strict in monitoring compliance from their suppliers and sub-contractors.
I wouldn't expect it to be otherwise.
MB have a reputation to uphold, and will always insist on compliance from their suppliers.

However ... I've worked in inspection for many years and I have seen some very-reputable companies attempt to get away with some very-dodgy practices over the years.
A number of big players (particularly in off-shore oil and gas) have clauses written into their contracts stating that materials of Indian or Chinese manufacture "shall not be used".
The problem is that there are companies in Europe buying in materials from the Far East and then deliberately (and criminally) falsifying the QA paperwork to mislead buyers into thinking that they are buying a product sourced in Europe.

You may find that brake discs is only one element in a very-dodgy area.

Just for the record ... I do inspect some very-good materials sourced in China.
The Chinese are improving manufacture at a very-fast rate.
For the present, there are some pretty-poor players in the game.
However - The number of good Chinese manufacturers is clearly on the increase..

 

[johnsco]

You coulda just flatted them off by rubbing them on a sheet of 140 laid on a flat surface.

They were pretty bad.
They had worn unevenly due to the disc surfaces.
I would not want to have re-used them ... Especially on new discs.

 

[WDB124066]

I only use Genuine parts. The OP's rotors are Genuine, and look like they have failed[...?] Brake rotors are a cheap part to make and will be subbed out accordingly. I am one of those owner Organisation Inspectors, I have been in too many workshops and too many factories all over the planet to have a great deal of faith in any simple production casting facility in the third world, hence the thinking out aloud about hardness testing. The common NDT methods will not tell you much about the microstructure other than cracks and viods etc, but what I was particularly interested in is the underlying microstructure of the iron, a simple hardness test can tell a lot, especially as they wear and are subjected to many many thermal cycles. If you can determine likelyhood of when they may crack based on hardness that would be a bonus as the hardness of the metal can be a reliable indicator on many steels and iron alloys.
Was wondering if the motor racing guys do this....??

It's just that if a rotor fails [and it may not be a gradual failure] death is quite likely on my roads.

I wasn't going to be as blunt as mentioning the Countries names johnsco, but to be frank I haven't worked on a project since 2004 where Indian or Chinese products were permitted. I was involved with building Meko 200 Frigates, nothing from the East at all in the entire Ship!

 

[johnsco]

Ah well ... The Meko 200 frigates ... built by Blohm & Voss.
How wise of the Germans to decline to buy materials from the East.
I only wish the same could be said about the Type 45 frigates built in the UK shipyards.
There are horror stories I could relate, but my work limits very-severely what I can say here.
My Avatar will give you a clue.
... and don't ask ... I cannot say.

I now only use brake components on our MBs that are from MB.
They are not even that much more expensive than the cheap copies.

 

[Doodle]

Well, the car is now down with Olly. I suspect much of the LH outer brake pad is now a fine dust covering the A272, given the scuffing noise on every revolution!

 

[Doodle]

Turns out I was wrong - the brakes look to be ok (if a bit tired and overworked) and the finger is being pointed at the centre prop bearing.

 

[Dieselman]

Turns out I was wrong - the brakes look to be ok (if a bit tired and overworked) and the finger is being pointed at the centre prop bearing.

I can understand the confusion...