2014 C300 Uneven brake pad wear inner v. outer
 

https://cimg9.ibsrv.net/gimg/www.mbw...0259a58e63.jpg
Inner pad material remaining
Hi all,
I was looking at my brake pads recently on my 2014 c300 sport 4matic with a the wheel off thinking I was due for a brake service soon given the amount of material left on the OUTER Pad of the front driver side. I popped the wheel off and found the attached picture. The inner pad had twice if not 2.5 times the amount of material on it than the outer pad did. Coming from DIY land, I'm used the inner pad wearing faster than the outer pad, esp since we're talking about front brakes here.

I didn't pull the other wheel yet to see if there was a pattern and I haven't checked the guide pins. You can see both pads are wearing evenly just not at the same rate so I'm skeptical of a pin having seized.

Both outer pads are wearing at similar rates.

The car only has 58k miles on it so I am assuming this is still the 1st set of pads. I'm the second owner.
No loss of brake fluid and the caliper itself looks really clean.

Anyone have this happen/know the reason why?

I'd be interested in reason particularly since these are single piston calipers on a C300, at least my preF and I don't see a 2 guide pin caliper becoming so reluctant to slide evenly that the inner pad had that easier a life. I have an 08 Mazdaspeed 3 with front calipers much like my MB. The inner pads on the front also wore significantly faster...I always used synthetic high temp brake grease on the pins, cleaned the bores/rubber boots, calipers were a slipping and a sliding on install but pad wear anomaly persists through the 3rd set of pads so far. That may be the nature of my Mazda but my C300 had even wearing front pads at the first change out. Any other C300 ft. brake pad observations out there ?

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I will definitely be digging in further once it warms up. i'm hoping to eek by on inspection next month so I have more wiggle room with timeframe. I am beginning to wonder if someone literally did a half assed brake job and only replaced the inner pads once upon a time and let the outer ones ride. I see on the service record that came with it that the brake fluid has been changed twice in 5 years. That's pretty intense for brake fluid change intervals. Looking at the aunt jemima in the brake fluid reservoir, I don't think it ever got changed since new....Maybe an indy or a dealer pulled a fast one on the previous owner....who knows. Rotors have got to be original.

This happens to me a lot with the floating caliper design in salty winter ontario. It's corrosion and lack of lubrication where pads are supposed to slide freely on the mount. I made the mistake of only inspecting the outer pad which appeared ok, much like you, but eventually the brakes started pulsating and grinding. Figured it was because my rotors were worn, I was only partially right. When I took apart the brakes, I figured the caliper might need rebuilding, but the piston retracted without issue and was smooth. I had to hammer the pads out of the bracket, though. Thats how badly seized they were. There was basically no grease left on the sliding surface. Put new rotors and pads on, and made sure to grease all the sliders very well (but not excessively, last thing you want is excess grease getting on the pad surface or rotors). All of this road salt is disastrous for floating caliper brake systems. Typically I service all the brakes before winter with new grease and a general cleanup, but this is what happened this year when I didn't.

https://cimg9.ibsrv.net/gimg/www.mbw...555ca49c56.jpg
Inner pad, very uneven wear
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Inner face of the rotor destroyed by terrible pad pressure and the pads not fully retracting because they were very seized up. The inner pad had actually pulled out of the piston "socket", so while the piston was retracting, the pad was not. Eventually, dirt and debris ruined the rotor surface. I should throw this on my record player to see what sort of sound it'd play..

In my opinion, this is a 99% slide pin lubrication issue. The other 1% is the caliper piston is hanging up.

Thanks for the pics and advice! This is a good problem to know about. When comes time to change these guys out, I will definitely be lubricating and polishing everything well. This has been a southern Virginia car for almost all of its life so salt use is not unheard but an order of magnitude less than ON. Or they just dried out because they're 5 year old original pads that haven't been serviced yet.

Check the tie rod end. Bad tie rod or bad ball joint in the lower arm or thrust arm can cause the uneven brake pad wear.