W204 brake pads handed - why?

[JamesG66]

I recently changed the front discs and pads (@33k miles) on my W204 C350 CDi, with genuine parts bought from my local dealer.

It all was going fine, and with driver's side (R) done I started on the passenger side (L) when I noticed that the inner pad seems to be handed, as this photo shows:

Realising my mistake I compared the original pad with the new pad and the only part that looked asymmetric is the backing material and the fact that it has an "L" on the back. So I carried on, and figured if they squeal I'd swap them over, but they are silent.

Today, about 300 miles later, the car is in for a service at MB and they pick up that the pads are in the wrong way round. Again, it's no drama for me to change them but I've never had handed brake pads before. The wear sensor fits fine with the pad on the "wrong" side so it's not that.

So what is the reason for them to be like that? Anybody know?

 

[MancMike]

I don't know either but I've seen the arrows on non-OEM pads too.

It's fantastic that they spotted this though! I'd be well pleased.

 

[Will]

I recently changed the front discs and pads (@33k miles) on my W204 C350 CDi, with genuine parts bought from my local dealer.

It all was going fine, and with driver's side (R) done I started on the passenger side (L) when I noticed that the inner pad seems to be handed, as this photo shows:

Realising my mistake I compared the original pad with the new pad and the only part that looked asymmetric is the backing material and the fact that it has an "L" on the back. So I carried on, and figured if they squeal I'd swap them over, but they are silent.

Today, about 300 miles later, the car is in for a service at MB and they pick up that the pads are in the wrong way round. Again, it's no drama for me to change them but I've never had handed brake pads before. The wear sensor fits fine with the pad on the "wrong" side so it's not that.

So what is the reason for them to be like that? Anybody know?

Not sure - are they chamfered slightly more on one side, as in the leading edge? Only other thing is the semi-circular cutout on the backing material - is that in the same place on both pads (?)

Interesting to note - someone bought aftermarket parts from a 3rd party supplier recently and was given TRW items. They said they'd never heard of them (and assumed they were a cheap brand I guess) and weren't happy. Looks like MB do in fact use them as an OE supplier

Plenty of TRW bits on my 911 too, and other German (VAG) cars I've seen.

 

[grober]

Mercedes-Benz W204 Front Brake Caliper Replacement - (2008-2014) C250, C300, C350 | Pelican Parts DIY Maintenance Article

 

[grober]

https://youtu.be/0ButRvF9GSE

Shows the sliding pins quite well but doesn't answer the question.
[YOUTUBE HD]0ButRvF9GSE[/YOUTUBE HD]

 

[grober]

I am lead to believe that the brake pad wear sensor is only on the right side??? front and back?

There are also different drillings on the disc pads for the wear sensors to go in depending on the model and right left position
detailed in AH42.10-P-003-01CW which I can't find on the web just yet.

 

[grober]

Here you go.

 

[ktos92]

One week ago I have change my rear discs and pads, I was considering buying original OEM parts from my local dealer but after I have hear the price of 250EUR just for the parts I have bought it TRW discs and pads for my W204 C180 AMG Line. I had compared the look of them to the original one and there is no difference at all :-D The only thing that is missing is MB logo. Regarding break wear indicator not every W204 has the one on the back. It depends on the engine type - for example M271 engines weren't fitted with the rear break wear sensor. This is what I have read in the WIS.

 

[OneForTheRoad]

nice genuine parts made by trw . mays well just put any pads in. :bannana::bannana:

 

[grober]

dup

 

[grober]

I can only surmise these pads are multipurpose intended for several models in several configurations. I can only guess that the holes are positioned at different depths in the pad material such that the pad renewal sensor signal comes up at different wear thickness perhaps to accomodate different brake disc cross section? I guess the motto of the story is to pay very close attention to the existing brake pad/sensor setup in your car before any pad /sensor change to duplicate it exactly.

 

[JamesG66]

Thanks for the all the responses.

Regarding the new pads, the chamfering appears to be the same on either side as this photo shows.

(I suspected I could have got a few k more miles out of the original pads as it goes.)

The soft layer of supporting material on the backing plate has a cut out which is in a different area depending on which side they are fitted though, which was the only difference I could see. From what I can tell its job is to prevent any noise and yet, from what I read, seems to be omitted from aftermarket pads.

And finally, in this case, the holes for the sensor are identical for either side pad. I've inspected my old pads to double check but they fact that I have them in the wrong way but the sensor still fits indicated that anyway.

So, still a bit of a mystery but as already said by another poster, it's always worth checking everything carefully before fitting.

Out of interest, how much labour does a dealer charge to change discs and pads these days?

 

[ktos92]

For the rear I was qouted in Ireland 240EUR for the parts plus labour. Everything in total was 350EUR which I think is a bit expensive.

 

[gianton]

For my S204 C250 CDI, cost of parts all four corners €260 from eBay (ATE rotors & pads) and €40 labour at my local indie. At dealership I was quoted double that price €600 (parts & labour). That’s in Greece.


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[JamesG66]

Brief update. I was investigating some front end shimmy this weekend and since I had the wheels off I swapped the pads around so they were correct. I've done 2k miles since fitting them. Went for a drive afterwards and there was absolutely no difference at all which, to be fair, was exactly what I was expecting.

So I still don't really know the significance of them being "handed" but it doesn't appear to be that critical.