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2 sets of warped AMG discs!

Discussion in 'Suspension, Steering & Brakes' started by grayb, Mar 29, 2011.

  1. grayb

    grayb Senior Member

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    Just thought I would post our experience of problems with replacement AMG discs for our W209 CLK55.

    We had new OE discs fitted by our local garage in April 2009, using genuine parts supplied by the nearest MB dealers, Tonbridge. By autumn 2010, it was apparent that the discs had warped - in no more than 10,000 miles, with only reasonable use (i.e. no track days! and mostly motorway miles). Our local garage referred the problem back to MB Tonbridge, who had the car in, checked the brakes, agreed they were warped and replaced the discs (with new pads) FOC under the 2 year parts warranty. Very helpful, cleaned the car etc. etc.

    Come this February, we still weren't happy with the brakes. Whilst the car was with Colin & Dave at MBS we asked them to check the brakes. The rear discs were shot - ok, we had never touched them so that's fine. However, the guys said the fronts were warped again as well!!

    Back to MB Tonbridge yesterday. Yep, they agreed and replaced the discs and pads again. Very helpful and apologetic, cleaned the car, can't fault their service. However, they did point out that the original warranty is up next month and that even if these new discs warp again, then it will no longer be covered.

    Now, given the track record so far, I am not confident that the discs wont warp again. I think I may have to write to MB to ask what they think of the questionable quality of their discs and on why a brand new set should not be covered by a new 2 year warranty?

    Incidentally, we drove our C43 for 5 years and only changed the front discs once in that time...
     
  2. television

    television Senior Member

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    The main reason that can cause them to warp or go out of true is if after a hard stop the foot remains on the brake pedal.

    Other than that just cheap cast iron, a very unstable metal at the best of times
     
  3. Bolide

    Bolide Senior Member

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    Are they truly warped - and what is the runout if they are? Next question is why?

    If this was a common problem I would expect there to be more mentions of it on the forum. As it doesn't seem to be common what's different about your car?

    It might be instructive to put some thermometer labels on the calipers to see what temps they are getting up to

    See
    http://www.temperature-indicators.co.uk/

    Nick Froome
    www.w124.co.uk
     
  4. Naraic

    Naraic Moderator

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    I know what you mean...but, as the pads are always abutting the discs, what difference does it make keeping your foot on the brake pedals.
     
  5. television

    television Senior Member

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    If you do a hard stop so that the disc get very hot, if you keep the pedal depressed then uneven cooling takes place causing the disc to warp or change in shape, the brake pads and caliper can act as a heat sink, or in reverse, and the natural cooling down is interfered with. The pads can also leave a footprint on the disc.

    With any cast iron object the heating and cooling is the most critical stage of any work, hence the welding of engine blocks is not easy and metal stitching is the way to go
     
  6. _Taz_

    _Taz_ Senior Member

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    part of the problem with these calipers ( I'm assuming they are like the famed Bremobs on my other car ) are that if the PADS aren't floating as meant to, then they will also bind = increased hot running, not to mention causing hot spots when you stop after coming off a motorway for example, the pad surface actually diffuses into the cast iron ( plus it also changes its composition ).

    the only way to cure this, is oddly enough to do several HARD stops ( on a private road ) without coming to a FULL STOP & repeating a few times, IT does work.

    other than that, or buy better discs... you could always push the boat & have 2 piece floating discs, again it's the cost versus what you want out of your setup :D
     
  7. television

    television Senior Member

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    Yes on my v70R i have knocking disc sometimes and a few hard braking without stopping it goes away, been gone for months now come to think of it
     
  8. OP
    grayb

    grayb Senior Member

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    I don't know what the run out was. I could ask the MBS guys if they measured it - but it was mostly felt through the pedal when you braked. If they weren't warped then why would MB Tonbridge have replaced them FOC twice?

    Perhaps the pads are binding as Taz says - but they have been in and out several times in this process and neither MBS nor Tonbridge spotted any other signs.

    And as for whether we have we done any hard stops and kept the foot on the pedal, we certainly do not drive the car in any way that an AMG is not intended to be driven. We are not boy racers nor has the car been tracked. The discs should be up to the use we put them too. We have owned plenty of fast cars that haven't suffered like this - from the C43, through an XJR, 944 Turbos x 2, Fiat Coupe Turbo etc. So perhaps there is something else going on?

    It would be interesting to know what Colin and Dave think...
     
  9. grober

    grober Senior Member

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    Its sometimes difficult to get your head round this but I will try to explain.

    You initially purchased a set of front discs from MB. These had a 2 year warranty and when they warped they were replaced FOC [ that's the important bit] as part of the 2 year warranty you originally purchased with the discs. They are still covered by the remainder of the original warranty. However you did not pay for the new discs or their implicit warranty so they remain unwarranted after the original warranty expires . If you think about it Mercedes could be replacing discs ad infinitum by your your reckoning which is just plain suicide from a business point of view. Buy another pair and you will get another 2 year warranty. Not many disc suppliers would even give you 2 years! That doesn't detract from the fact they should have lasted a bit longer but modern disc and pad material seem to have increasingly shorter lifetimes nowadays. I don't know who makes the MB AMG discs---Zimmerman-Brembo ?? but I have always found ATE to be a good product if they make discs in that size.
     
    Last edited: Mar 30, 2011
  10. jberks

    jberks Senior Member

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    A warranty is part of your sales contract and is not connected to that actual phyiscal component you bought. Think of a warranty not as a guarantee that the part will last that long, but rather a guarantee that for the period of the warranty, they will acccept responsibility for any further expense as a result of the warrantied part.
    In theory, it should be in their best interests to ensure the part outlasts the warranty, or they're paying for each subsequent replacement.
     
  11. wireman

    wireman Senior Member

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    Adding temp labels to the calipers wont tell us much, its the disk that's over heating.
    A thermochromic paint will be required to deal with the possible 600 degrees plus.

    The sticky pad theory sounds favorite to me, pre heating the disks so that they get above a sensible ~400C+ temperature in normal use will result if the pads are even only slightly rubbing.
     
  12. television

    television Senior Member

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    True with cast iron the the critical stage is 400c plus, I think though that if the brakes were rubbing / binding then the smell of the hot brakes would be a givaway on this. Could not it just be a bad batch of disc
     
  13. OP
    grayb

    grayb Senior Member

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    And surely over several thousand miles the pads would wear unevenly if one caliper were sticking? If so either MBS or Tonbridge Merc would likely have spotted it...

    Oh, and I take every one's point about the warranty. Doesn't mean I like it though ;)
     
  14. television

    television Senior Member

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    Yes you would have worn a set out in no time, one must bare in mind that only 1 disc was at fault here, not both
     
  15. drmw

    drmw Moderator

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    I beg to differ on this. My understanding is that when a part is replaced, the warranty for that part starts again. Personal experience with a PSE pump. It was replaced last year - say January - new unit goes down February this year. I call into MB & say the pump fitted last year had failed within the new 2 year warranty cover, please replace again.

    They did and if it broke next March, I would get it replaced yet again under warranty.

    I understand what you say about commercial suicide which is why they should manufacture to higher standards in the first place. ;)
     
  16. jberks

    jberks Senior Member

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    Not how the law works afaik, although on a goodwill/reputation basis you may well get them to change it anyway. All law is based around the original "sales" contract, and that commenced when the item was bought and fitted. The warranty starts at that point and ends when it ends. Remember, the warranty applies to the sales contract, not the physical component. How many times the component is repaired or replaced during that warranty period is irrelevant. This can be a tricky aspect of a new car warranty. If they replace a component in year 3 for example and it fails again in year 4, technically there is no warranty covering it as the 2 year used parts warranty on that component only applies if the part was sold to you, which it wasn't.
    In reality, in most cases there's some lattitude but that is from MB, not the law.
     
  17. ernieh

    ernieh Senior Member

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    Warranties

    I think jberks has explained the situation fully and accurately........Back in the days of the Morris Marina, I had a colleague who had a 1.8TC which seemed to be always breaking gearboxes. He was not a coarse or hashy driver and never had trouble with previous cars, so it was difficult to see what was causing it. If I remember correctly, he had 5 gearboxes under the original 12 months warranty, but when the last one went at 13 months, he had to pay for it. Needless to say that was the last one he paid for as he then sold the car for another Marina, which was OK for the 2 years he had it.

    There was no good will in these days....when the warranty expired, you were on your own!


    Ernie
     

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