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I'm on my second Mercedes (CLK then C class). I gather that due to the design, where the pads grip slightly inside the edge of the disc, the discs will always become lipped.

Whenever the pads have worn down the Mercedes garage always recommend replacing the discs as well as the pads because of the lipping.

Is this just a money maker for them or can I safely just have the brake pads replaced assuming the disc is still thick enough, even though it is lipped?

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  • It's probably a money maker. The discs do not usually need replacing as often as the pads.
    – Weather Vane
    Commented Sep 6, 2019 at 12:16

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This does depend on the grade of pad and the original thickness of the disc.

Go back 10 or more years and discs were thicker as the drive for fuel consumption and total weight was not as severe, which means if they can fit thinner discs with a reasonable life they will...

I have just had to replace discs and pads after 70000km - the pads needed changing and the discs at the minimum thickness. Not bad actually, as my previous car ate pads every 15000km and discs every 30000km. And my driving style has not changed between the two cars (both manual) and yes, all my bad habits are ingrained :) ...

So, for the "newer" generation of cars changing pads and discs together seems to be about right.

The practice of skimming discs, well, if there is enough meat left then fine but if they have done 50000km plus then probably not.

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Pretty much all cars have this, and depending on the brake use and the brake pad compound it may wear out the brake rotor too.

It really depends on how bad the lip is, usually manufacturers release certain specs and also wear specs found in repair manuals. As a rule of thump, if the lip is more than 2mm I would consider replacing the brake rotor too.

Generally, the reasons why you need to replace the rotors are 2, if you wear out the rotor too much there may be weaken and in extreme cases start using the inside cooling veins for rotor material. The other reason is for the best possible performance.

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There is an alternative to replacing the discs, depending on how much is left on the lipped discs. It's possible to have your existing discs turned on a lathe to remove the lips and present a flat braking surface. I don't know where you live but there are manufacturers who make "on-car" brake lathes and local garages with this technology won't charge much to skin a set of discs. I have no affiliation with this company but a quick google search unearthed them; https://skimmydiscs.co.uk/your-nearest-service-centre

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  • Skimming a disc won't make the worn part any thicker. It is worn because this is the area where the pads rub. The lip is there because the pads have not worn it away like the rest of the disc. The only merit I see of removing the lip, is when a different pad is fitted which overlaps the lip.
    – Weather Vane
    Commented Sep 6, 2019 at 12:12
  • It'll return the discs to a flat surface so it'll remove any warping. Plus if the lip interferes with the pad in any way, skimming them will significantly reduce running in time. I agree that if the lip isn't in the contact patch of the pad, there is little point removing the lip.
    – Steve Matthews
    Commented Sep 6, 2019 at 12:17
  • That's true, skimming the entire disk instead of just the lip will remove any warping, but will make them even thinner, so it is hardly an alternative to replacing a worn disc.
    – Weather Vane
    Commented Sep 6, 2019 at 12:18
  • If the end thickness is within manufacturers tolerance, it worthwhile. Very much depends on the state of the discs to begin with I guess.
    – Steve Matthews
    Commented Sep 6, 2019 at 12:19
  • I have removed the lips ( rear wheels) by turning them with the engine and holding a file on them until gone.
    – blacksmith37
    Commented Sep 6, 2019 at 15:51

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