Brake Caliper & Pad Question - PeachParts Mercedes-Benz Forum

RML · #1 01-05-2014, 01:28 AM

I have the rear brake calipers from my 84 300D on the bench for rebuilding. They were not engaging at all and I was stopping with totally the front brakes. So I have them all apart (not the casing) and am cleaning them up. It was difficult to get the pads out of the slots because of the rust, but now that I have the rust cleaned up, the pads still go into the slots with some difficulty. I am wondering if it is common practice to file the side of the brake pad so they slide in easier, or is there a danger of getting too much play and having the pads vibrate and chatter when engaging.

vstech · #2 01-05-2014, 01:35 AM

if the pads are not rusty, there's no reason to file them... clean the calipers better.
be sure to grease the spot where the pads touch the calipers. it aids the pads release.

Stretch · #3 01-05-2014, 02:45 AM

I agree don't modify stuff beyond the realms of cleaning. If the pads are of a really cheap brand you might want to consider something more prestigious!

toomany MBZ · #4 01-05-2014, 08:26 AM

Make sure the pistons are pushed back far enough to allow the pads to slide in.

No need to file anywhere.

tangofox007 · #5 01-05-2014, 09:55 AM

Quote:

Originally Posted by RML

I am wondering if it is common practice to file the side of the brake pad so they slide in easier...

By chance, does the friction material overlap (extend beyond) the the upper and/or lower edge of metal backing plate?

t walgamuth · #6 01-05-2014, 10:34 AM

I grind the edge if they are too tight.

Diesel911 · #7 01-05-2014, 12:08 PM

All the cheap ones I used have fit. But, I would have no issue filing a bit off if they were a little sticky.
If I had that happen to new locally bought Brake Pads I might take them back as the Local Auto Parts Store is close by.

BWhitmore · #8 01-05-2014, 12:12 PM

Definitely do not file the pads. Appropriate disc brake pad lubricant is the best to use but not excessively.

t walgamuth · #9 01-05-2014, 12:38 PM

Quote:

Originally Posted by BWhitmore

Definitely do not file the pads. Appropriate disc brake pad lubricant is the best to use but not excessively.

why not?

Clarence Thomas · #10 01-05-2014, 01:01 PM

Quote:

Originally Posted by RML

It was difficult to get the pads out of the slots because of the rust, but now that I have the rust cleaned up, the pads still go into the slots with some difficulty.

The issue is the fact that corrosion is constant over the years on the calipers and cleaning them up requires more than a cursory pass with a wire brush. If you feel the surface where the pads ride, it will not have a good finish, despite the fact that the surface rust is removed. It is necessary to take a file and remove the pitted surface so you achieve a satisfactory surface finish. Add a bit of grease designed for brake calipers to those surfaces and the pads should now insert without any issues.

whunter · #11 01-05-2014, 01:30 PM

Quote:

Originally Posted by Clarence Thomas

The issue is the fact that corrosion is constant over the years on the calipers and cleaning them up requires more than a cursory pass with a wire brush. If you feel the surface where the pads ride, it will not have a good finish, despite the fact that the surface rust is removed. It is necessary to take a file and remove the pitted surface so you achieve a satisfactory surface finish. Add a bit of grease designed for brake calipers to those surfaces and the pads should now insert without any issues.

File the caliper to a clean smooth surface, a light coat of anti seize is also a good idea.

.

BWhitmore · #12 01-05-2014, 01:35 PM

Cleaning up the caliber (filing) seems to be the best way to go. If the pads do not fit that would be a pretty good indication of a poor quality pad.

t walgamuth · #13 01-05-2014, 02:22 PM

never had any trouble grinding the edge a bit.

dude99 · #14 01-05-2014, 02:32 PM

Sometimes the backs of pads are powder coated (or painted) and they get high spots on them. I have taken a knife a scraped the paint off these edges making a pad that was difficult to fit slide right in.

RML · #15 01-05-2014, 02:50 PM

The pads are Texar. I ordered them from this site when I last replaced the pads. I stay away from cheap parts as I almost always pay the price later.

The pistons being out too far are not an issue as they are not in the caliper right now. I am still cleaning the calipers.

The friction material does not extend beyond the metal backing plate.

I have cleaned up the surface rust on the calipers with a wire brush and did a cursory pass by with a file but did not want to get too aggressive. I would not say that surface is without pits. Assuming that the pads are sized correctly, I think I need to use my file on the caliper a bit more aggressively to achieve the smooth surface that whunter is referring to. I definitely do not have that yet.

Regarding my next step while I have the calipers out, I am planning on priming and painting them. I considered having them sand blasted and painted but I really do not want to get that carried away with this project. I am wire brushing the caliper body but cannot really get it down to a shiny surface everywhere because of all of the curves and crevices. I considered using Por 15 to convert any remaining rust and then using an etching primer. Not sure if I should just use the etching primer and skip the Por 15. I don't want to go to a bunch of trouble just to find that after a few months the paint has all peeled off. Any suggestions?