2017 GLS 550, 55,000 miles. I'm replacing pads and rotors as a result of check brake pads warning. Very different thickness between inner and outer pads: 0.080" left on the inner (wear sensor side) and 0.360" outer pad remaining. Not sure if you can see in picture below. Guess this means my floating caliper wasn't floating. The caliper pins had a layer of black gummy substance that I was able to remove with a shop cloth.

Is this common? Symptom of any bigger issues? Do I need to clean my pins periodically (every 10K miles, other?)
Is there anything else I should do/check as part of this service besides cleaning the pins and the bores they go into so that I get even inner/outer pad wear? FCP Euro says that the front pins should not be greased, and there was no grease in the pin boot.

Dave


Right front pads, outer left (0.380" thick), inner right (0.080" thick) .

I believe the calipers are full floating calipers on the non AMG models... usually this a symptom of the caliper not being able to freely slide on the pins. more than likely replace the pins.

EDIT... I should read the post and not just look at the pictures... LOL Looks like you are already on the right track... possible someone put some "lubricant" on the pins at some point that dried up!

Are you a left-footed braker?

No, not a left-footed braker and certain that I don’t ride the brakes.

This was a used, CPO purchase and is my first brake service for the vehicle. Probably was one performed by the prior owner.

The rear pads were much more uniform inside vs outside.

Lots of folks were taught to left-foot brake, and I see this all time out on the road -- a car in front of me whose brake lights randomly flutter on and off. I know the driver isn't moving his foot back and forth, gas to brake to gas. He's resting his left foot on his brake pedal. A possible consequence of this is uneven pad wear as the piston side of the caliper pad is rubbing on the rotor while the other pad is not (the piston side pad usually makes rotor contact first).

I agree with @thtguy -- someone used paste or lubricant when they installed the brake pads. Mercedes work instructions call out specifically to *not* use paste or lubricants on brake pads or other brake parts (e.g., caliper pins) -- I suspect for exactly this reason.

I would clean everything up, with lots of brake clean, if the pins have any pitting or stickiness or anything not perfectly smooth, I would go ahead and replace.