Brakes grinding in 1991 124, why?? - PeachParts Mercedes-Benz Forum

Grdenko · #1 07-17-2007, 08:25 PM

Hello forum, long time no see.

Heres the deal, about 23k miles ago i got new pads AND rotors (front only), done by an indie shop. The pads i think are OEM type, the rotors are not though, theyre slotted, and rather expensive.

About 5k miles ago i started noticing a strange grinding from the front brakes. The grinding doesnt happen always, but about 1/2 the time under these conditions:
1. seems to be louder when theyre hot, but not necessarily
2. only at low speed, below 15mph, the slower the louder
3. the harder braking, the louder

this, of course caused me some concern so i put 'er up on a jack and took a look at the pads/rotors. Everything looked fine at first, plenty of pad left etc. but after closer inspection heres what i saw:
1. the outer pad was wearing significantly faster than the inner pad
2. the pads were wearing unevenly, more toward the outside edge

i dont know if either of those things is a big deal, but i thought i would note them.

here are my ideas about the grinding, it could be from the slotted rotors, but i never heard this grinding in the first 18k miles on them. or maybe the pads are a different type than i had before?

i dunno, but the noise drives me nuts so im gunna try changing the pads anyway, so id like to get some tips on changing them and what kind to use.

thanks for all of your help.

vstech · #2 07-17-2007, 10:05 PM

slant inner/outer, is a sign of loosening bolts or a warped mount. also it could be improperly matched piston/bore on a rebuilt caliper. not a good sign.
I would pull the wheels, pry the pads away from the rotor, and try to wiggle the caliper, if it moves AT ALL get a new caliper and mounting bolts. if it does not move, pull the pin/spring and remove the pads, very simple, you will understand when you look at it. then wiggle the pistons in their bores. if they move at all, get a new caliper. if neither of these are a problem, you may have a bent mount. have a shop inspect.

Grdenko · #3 07-19-2007, 04:29 PM

calipers werent loose, and theyre original, not rebuilt ones. I didnt try wiggling the pistons inside the calipers though, but i did already have a shop look at it (before i posted) and they couldnt find anything wrong. Still making a horrible noise though.

The uneven wearing of the pads may be exaggerated because they are pretty near the end of their life. The inside pad had about 4mm left on it and the outside pad had about 2-3mm on it, 2 on the outside edge and 3 on the inside. Im not really very concerned about it other than for helping diagnose the noise.

Before i get it back up there id like some recommendations on new pads so i can have them to put on. Fastline has like 6 different kinds so some tips would be helpful.

thanks

rrgrassi · #4 07-19-2007, 04:38 PM

Have the calipers ever been rebuilt or replaced? You can get a piston sticking also, and that will cause uneven wear, and since our system uses rigid, piston opposed calipers, the piston that is the most able to move will press on the rotor with more pressure. Because of a little bearing play, it can be enough to make the rotor deflect a little resulting in the outside or upper part of the pad to wear more. This is also bad for the bearings.