grooves one rotor only???
 

1. I have been changing break pads since high school and on Mercedes cars about 17 years now I am really stomped over this recent encounter I have.

2. A scratching dragging sound was coming from the rear driver side, after inspection trough the rims opening I see grooves on the rotor. Well time for new pads normal right, NOT.

3. Well ordered the new pads and got everything apart and after looking there seems to be about six months of life left on these babies, what gives? There is a slight wear difference from the outer and inner pads the outer has a little more wear on them. Also a lot of rust. Of course the grooves on the rotor not the two big ones like you see when there is so much wear that it’s down to metal to metal then the rivets. But a bunch of little ones like on a record.

4. I check the other side and no grooves! But the pads seem to have less life about 4 months left. The wear is the same on both outer and inner pads. A little less rust. The only thing different about this side I recall is the bearings was replaced about 3 months ago.

5. The following are things done on both sides as I recalled:
. a. Rotors were replaced about 6 years ago.
. b. Calipers were replaced about 5 years ago.
. c. New pads 2 years ago.

6. With these statements known above, the following are question I have:
. a. What would cause grooves?
. b. What would cause uneven wear for outer and inner pads?
. c. What would cause uneven wear from side to side?

7. As for now I’ll try to get my moneys’ worth and ride them for the duration of the remaining pads unless youall can tell me something different.



Thai GI

Sounds like the caliper may be sticking on that rear wheel. Did you take a look at the seals on that caliper? I'd start with that for sure. Good luck.

I agree with Jason, sounds like you may have pistons sticking in the caliper. You may also have a problem with a collapsed brake hose to the calipers . Its always a good idea to replace the hses when you replace or rebuild calipers and also a good idea to do calipers in pairs.

both were changed
 

1. Oh, the calipers were both changed also the hoses at that time.

2. I’ll check that, don’t have one of those fancy kits so I think I’ll do it by removing the pads and have the wife slowly step on the breaks and take a look, I guess. :D

Thai GI sends…

BE VERY CAREFUL with taking the pads out and having someone step on the brake pedal. You can easily over-extend the pistons inside the caliper and then you have a royal pain to deal with. Put something inbetween to fill in where the pads and disk were.

Ditto on that. Can't you just inspect the seals around the caliper and see if they are blown out or not? If you can hear it, that is almost indication enough it is sticking. Big ole pain if they go out too far. I know someone who did that once...a long time ago.

Abrasive grit like sand on the pad will groove the rotor and prevent pad wear, while reducing braking efficiency.

I'd replace the pads and have the rotor turned if the grooves are more than 0.020" deep -- this is a rather deep and obvious gouge that you can catch your fingernail in. If they are small, just replace pads.

A small stone tossed up by water or the wheel that gets behind the dust shield and lodges up by the pads can do the same thing -- I got a bit of limestone stuck behind the dust shield on the 220D that screeched so badly I finally pulled the rotor to get it out, it was driving me nuts. It had started a nice gouge, too, but it was shallow enough I left it alone.

Peter

rotors grooved
 

I have had both problems with the gouging of the rotor.
piston sticking and pea gravel
With the temps so harsh and variations of being in the elements and then in a nice warm garage the moisture begins to come into play in the brake lines
at the calipers, lack of not flushing the lines will hang up a pad.
The pea gravel the city here use for traction at intersection, curves and ect.
It's a must for safety, but the pea gravel will work it's way in between the rotor and pad.

clean and grease
 

1. Well I check the calipers and it was in good working order, I just clean around the area with a brush and clean the pads then apply a little copper grease. Will give it a month or so to see if the rotors will smooth out I think this should the trick.

2. I think that the pads were just seized and was rusted on the calipers. The car was in Iceland and after shipment it sat for about 5 months the combination of salt and moister might have done this.


Thai GI sends…

Two things are very bad for MB brakes -- running the rotors down too thin, sticking the calipers, and overheating them and letting them sit for extended periods.

I think extended sitting leads to the collection of water under the dust shields, and hence corrosion of the area of the caliper bore above the piston seal. This area does not appear to be chrome plated, for some reason, and any roughness here causes the piston to stick.

I would remove the caliper and replace the piston seal, dust boot, and heat shield. It will seem to work OK when prying it back, usually, but still stick once hot in use.

And rusty pads will certainly cause trouble -- I was getting concerned that I had 60,000 miles on the front pads in my Volvo with no signs of worn out pads, although I had some squealing issues (not uncommon on the 740). When replaced them, I discovered that they had been rusted in place for some time -- took a large hammer to drive them out AFTER lifting the floating caliper! I greased the new ones after scraping off large amounts of rust. The old pads were worn tappered from being more stuck on one end than the other, causing the screech. They didn't work well, either -- I was stopping only with the rear brakes!

Peter