W204 C350 minimum disc thickness

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merc07

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Car
C350cdi & C220cdi
As above, anyone know this for the drilled sports pack discs.
I changed the pads at 70k, hardly any lip at all at the time, now done 110k and the pads still look like new..
 
Can that be read after 110k miles ?
 
After cleaning the disc edge

 
Cheers, if I have time over the w/e I'll check.
Just been through my records, I changed the pads after 87k, not 70k..
 
If you input your vehicle details into one of the online factors, eg eurocarparts (others are available ;)), select front discs and then 'fitment' details it should list the disc's sizes, including min thickness.
 
Nothing showing on europarts ?
Couldn't see anything on the disc themselves either.

These are genuine discs, measured one side at 30.5mm, from the lip to lip is 32.5mm.

They ok then as far as the thickness goes ?
 
put up a pic. how big is the lip thats formed
 
If you're saying original thickness was 32.5mm and it's now 30.5mm, I would suggest that they need changing; you've lost 2mm of disc thickness which will make a difference in heat dissipation, let alone anything else.

I don't know if the link relates to your car, but interestingly it shows disc thickness at 32mm, minimum 30mm, which would indicate that yours is at or virtually at minimum thickness.

 
Lip is 32.5-30.5 = 1mm per disc surface, I'll take a pic tomoz. See if you think the surface is ok to use the pads already in there if I swap out the discs as plenty of life left they look almost new - Or is always a pad change with discs..

Cheers for the link, @tonysmb

Yep mine are perforated/vented, guess original are brembo also so min 30mm, just about dead.
 
You get atleast 2 pad changes per disk change.

Only MB dealers change them both together....
 
You should always fit new pads if you fit new discs, however, how many sets of pads are needed during the life of a disc very much depends on how you drive/brake.

It's a generalistation but many now find/recommend that discs need replacing at every other pad change. Having seen people who have mistakenly measured their discs (one example) and pads (a different individual), both had problems, despite having assured themselves that their brakes were within spec; in one case the disc broke when subject to an emergency stop and in the second case the 'noisy brake' was caused by pads worn down to the metal backing, which the individual had mistakenly measured as part of the pad thickness.

For the price of a set of pads, I wouldn't consider using old pads on new discs, even if they look to a reasonable life left, but ultimately, it's an individual decision. Garages will (should?) err on the side of caution because if there's a problem later on, they would be classed as 'experts', whereas the customer wouldn't.
 
Back when I first started selling cars....about 1987, disc changes were quite a rare thing.....perhaps a set in a cars 100,000 mile ......so perhaps 5 or 6 sets of pads per disc life. But as soon as they replaced the asbestos in pads disc wear skyrocketed to more like a set of discs every other set of pads. That's progress!!
 
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Back when I first started selling cars....about 1987, disc changes were quite a rare thing.....perhaps a set in a cars 100,000 mile ......so perhaps 5 or 6 sets of pads per disc life. But as soon as they replaced the asbestos in pads disc wear skyrocketed to more like a set of discs every other set of pads. That's progress!!

I've been thinking the same.

Wear limits on discs must have become more conservative which I struggle to believe is down to structural integrity, more a claimed issue with heat dissipation. I recently replaced my front discs that were only just down to the limit and structurally there was masses of metal remaining. In fact the damn things weighed a ton compared to the discs on my old 190e. Considering that's all unsprung weight. substantially heavier discs are not progress either.
 
My driving consists of either Bristol traffic, so max 20mph, or motorway on cruise - don't use the brakes.
Hence 87k for the first front pad change and the discs were fine - now at 110k, plenty of meat on the pads but discs getting low.

Think I should have just done discs and pads last time instead of '2 sets of pads to a disc' thinking..

Attached some pics, should have took them with the wheels off..
 

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That looks to be quite a lip on the disc, presumably they've worn down evenly on all four sides of the front pair? It is a nuisance when there's still plenty of material left on the pads: I ended up replacing the original rear discs and pads on a 10-year old MB because the discs were starting to corrode but the pads, however, were hardly worn.
 
The min thickness is something to check then you change the pads. It's my understanding that if you are above the min thickness you are good for a whole new set of pads.

Disc failure due to wear is pretty much unheard of, unless you watch Just Rolled In on youtube where people often wear the disc down to nothing.

Having said all of that your discs are looking a bit old and crusty. In that case the internal venting tends to get clogged with rust which would affect cooling.

In terms of the pads - advice is always new pads with new discs - however if it's OK to fit new pads to old discs accepting that the pad will wear to match the surface of the disc then reversing that must be true too? If money is tight run the old pads across some sandpaper on a very flat surface and it'll restore the pad surface to as new. The problem here is the chamfer on the leading edge of the pads, if this is lost then the pads can squeal.

All that said, in your case, I'd be leaving alone for now and when a bit more worn changing the lot - pads, discs and if at the rear the brake shoes too.
 
Thanks for all the input, instead of worrying about them every time I drive...

Just ordered a set of genuine discs / pads, think I'll keep the pads and flatten them off as mentioned, I have an old heavy duty flat sanding plate....

This will do me a for a good 70k +, then all being well, I'll just fit the old pads next time...180k 🙄
 

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