BRAKE DISC WEAR

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Mickey
C Class
Posts: 33
Joined: Mon 13 Apr, 2015 12:04 pm
Model you own: w164
Location: Sutherland Shire, NSW

BRAKE DISC WEAR

Post by Mickey » Thu 11 Aug, 2016 12:09 pm

Just had my car serviced at my stealership. All is well except that he told me that I needed 4 new tyres (which I don't with 5 mm of tread depth left after 23,000km) and new front discs. I can do the brakes myself but how do I tell when the discs are worn to their wear limit? How much wear is enough? They look to be around 2mm below the disc edge but I haven't measured accurately yet. What is the limit? All opinions welcome.

mattml430b
C Class
Posts: 44
Joined: Sun 10 Jul, 2016 6:52 am
Model you own: w163

Re: BRAKE DISC WEAR

Post by mattml430b » Thu 11 Aug, 2016 12:29 pm

You need to measure your disc width. It will be written on the disc itself the minimum allowable width.
If you have a 2mm worn outer grove there is every chance he's correct.
What year and model is it?


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Bartman4800
300 SLR
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Joined: Fri 10 Oct, 2008 12:10 am
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Location: Perth WA

Re: BRAKE DISC WEAR

Post by Bartman4800 » Thu 11 Aug, 2016 1:15 pm

A minimum thickness is usually stamped into the perimeter of the disk.

If you say a 2 mm raised edge, that tells me your dealer is probably correct (but not on the tyres)

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T-Modell
SLS AMG
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Re: BRAKE DISC WEAR

Post by T-Modell » Thu 11 Aug, 2016 5:42 pm

If you have holes in the discs, there is a maximum length of the cracks starting from those holes. Maybe that's what your dealer meant.
Thomas
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Mickey
C Class
Posts: 33
Joined: Mon 13 Apr, 2015 12:04 pm
Model you own: w164
Location: Sutherland Shire, NSW

Re: BRAKE DISC WEAR

Post by Mickey » Thu 11 Aug, 2016 5:54 pm

mattml430b wrote:You need to measure your disc width. It will be written on the disc itself the minimum allowable width.
If you have a 2mm worn outer grove there is every chance he's correct.
What year and model is it?


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Thank you for the reply. I have a 2010 ML350 CDI. Bought it 2 years ago with 54,000km on it. Now it has 78,000km. The rear discs have less than 1mm wear. I replaced the rear pads about a year ago and bought new front pads thinking I would need them soon but the fronts are not down to the wear indicators yet.

mattml430b
C Class
Posts: 44
Joined: Sun 10 Jul, 2016 6:52 am
Model you own: w163

Re: BRAKE DISC WEAR

Post by mattml430b » Thu 11 Aug, 2016 8:39 pm

Original is about 32mm but have a look on the outer edge of the disc or it can be just on the inside edge of the disc face. Sounds like they are ok if you only have 1mm of wear.


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Mickey
C Class
Posts: 33
Joined: Mon 13 Apr, 2015 12:04 pm
Model you own: w164
Location: Sutherland Shire, NSW

Re: BRAKE DISC WEAR

Post by Mickey » Fri 12 Aug, 2016 4:49 pm

Thank you all for your input. I shall have a closer look at the measurements.

Mickey
C Class
Posts: 33
Joined: Mon 13 Apr, 2015 12:04 pm
Model you own: w164
Location: Sutherland Shire, NSW

Re: BRAKE DISC WEAR

Post by Mickey » Mon 15 Aug, 2016 5:27 pm

Had a look at my discs on the weekend. For general information, the front discs have a minimum limit stamped on them of 29.4mm. I have 30.1mm left on both sides. To be fair to the dealer, he probably pointed that out thinking that they won't last to the next service (once a year for me). For some people they wouldn't but they probably will for me. I had a Commodore SS which had 177,000km on it when I sold it and I never changed the brake pads or discs. And I had about 4mm of pad wear left. Anyhow, I will keep an eye on the wear and I figure that the pads and discs will wear out at about the same time so I will replace both things at once.
Thanks again for the use of your knowledge, guys.

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