Rear Brake Pad Replacement Question - PeachParts Mercedes-Benz Forum

Panzermann · #1 04-22-2007, 09:12 PM

So, I measured the thickness of the rear rotor on my 1985 300D and it was 8.1 mm, which is below the noted thickness in the book (8.3 mm) so I decided to replace it and the pads at the same time, although the read pads on it were not worn out.

I replaced the rotors with new ATE ones, which were thicker than the original. I think my read calipers are Bendix. My old pads had shims on them.

I go to put my new Textar pads in and thay will only fit partway, getting hung up about halfway in. I could not get them to fit, so I eventually reinstalled the old pads (minus shims) and waited to discuss this problem on the forum.

I noted that the Textar pads have some material, almost like a shim of sorts, glued to their back. It can however been easily removed and I suspected would allow the new Textar pads to be inserted. What to do? Remove these backign pads from the Textar pads, clean off the glue with some brake cleaner and the install them, if possible? Sand down the braking surface of the Textars so they fit? Do the Textars need a shim, even with the backing material?

toomany MBZ · #2 04-23-2007, 05:06 PM

I just took a look at my Textar pads, they do not have any shim type affair. My '82 has shims, don't know about the others. I've heard the shims are for squeal control, but can't figure out how. Don't know if they're necessary. I have a CD-ROM on the procedure, and that fella did not deal with any shims. Make sure you are installing rear pads, as the front pads are thicker. Your old pads should be fine, as long as they are 2mm, which is service limit.

carnut · #3 04-23-2007, 06:20 PM

You are retracting the caliper piston into the caliper PRIOR to inserting the new pads, correct? With the pads removed, simply use a large screw driver as a lever and push in the pistons slowly. Must be done on both pistons at each caliper. Once the new pads are in, depress the brake pedal two, three times to adjust the pistons to the increased thickness. As a general rule, the rotors will be below minimum thickness at the third brake pad replacement. I retract the pistons prior to removing the old pads, using the pads as the prying surface, then the new ones drop in like toast in a toaster!

t walgamuth · #4 04-23-2007, 09:24 PM

yeah, i bet you didnt get the pistons pushed all the way back.

tom w

Panzermann · #5 04-24-2007, 10:15 PM

Quote:

Originally Posted by carnut

You are retracting the caliper piston into the caliper PRIOR to inserting the new pads, correct? With the pads removed, simply use a large screw driver as a lever and push in the pistons slowly. Must be done on both pistons at each caliper. Once the new pads are in, depress the brake pedal two, three times to adjust the pistons to the increased thickness. As a general rule, the rotors will be below minimum thickness at the third brake pad replacement. I retract the pistons prior to removing the old pads, using the pads as the prying surface, then the new ones drop in like toast in a toaster!

So, you insert the screwdriver blade in to the space where the pad used to be, emerging from the other side and use it as a rod of sorts to apply pressure to the piston?

vstech · #6 04-24-2007, 10:25 PM

AAAACK, no! keep the old pads in, put the screwdriver against the old pads, and pry until the piston is all the way in.
John

t walgamuth · #7 04-24-2007, 10:56 PM

that is right. pry with a 16" screwdriver between the disc and the pad. don't worry about damaging the rotor. they are very very tough.

before installing the new pads clean the slots where they slide in and take a little off the sides if you need to to get them to slide in easily.

good luck,

tom w

Chris Bell · #8 04-25-2007, 02:54 AM

Quote:

Originally Posted by vstech

AAAACK, no! keep the old pads in, put the screwdriver against the old pads, and pry until the piston is all the way in.
John

I use the old pads and C-Clamp to push the piston back in, works well.

vstech · #9 04-25-2007, 07:23 AM

how do you get a c clamp to work on a dual piston caliper?
John

dannym · #10 04-25-2007, 08:00 AM

get some brake cleaner and spray the caliper down before putting the new pads in. Also put anti-squeal paste on the back and sides of the new pads.
I use a full can on each caliper.
Unless you like the noise then nevermind.

Danny

Panzermann · #11 04-25-2007, 11:38 AM

Quote:

Originally Posted by vstech

AAAACK, no! keep the old pads in, put the screwdriver against the old pads, and pry until the piston is all the way in.
John

OK I understand now. This must also be the reason that you change one pad at a time. Thanks for the input!

rrgrassi · #12 04-25-2007, 01:12 PM

Quote:

Originally Posted by vstech

how do you get a c clamp to work on a dual piston caliper?
John

C clamp works on a dual piston floating caliper. The dual piston fixed caliper is a different story as we all know.

I have heard it said that the is a caliper speader for this type, but have yet to see one. I just love how you try to push one back, and the other decides to move out. I guess that is the reason why you remove one pad at a time, unless you are replacing the caliper. I wonder how rebuilding them works...

vstech · #13 04-25-2007, 02:40 PM

Quote:

Originally Posted by rrgrassi

C clamp works on a dual piston floating caliper. The dual piston fixed caliper is a different story as we all know.

I have heard it said that the is a caliper speader for this type, but have yet to see one. I just love how you try to push one back, and the other decides to move out. I guess that is the reason why you remove one pad at a time, unless you are replacing the caliper. I wonder how rebuilding them works...

Yeah, that was my point.
on the 123/126 calipers they are fixed calipers. no way to put in a c clamp...
several threads have been here about rebuilding the pistons, they use a block of wood to hold one piston in place while they use air to blow out the piston they work on.
John

rrgrassi · #14 04-25-2007, 02:46 PM

Quote:

Originally Posted by vstech

Yeah, that was my point.
on the 123/126 calipers they are fixed calipers. no way to put in a c clamp...
several threads have been here about rebuilding the pistons, they use a block of wood to hold one piston in place while they use air to blow out the piston they work on.
John

I wonder how they do that. Seems like the wood would block both at the same time. Yeah those opposed piston calipers can be a pain, but they sure stop good!

Panzermann · #15 04-29-2007, 09:05 PM

Thanks for the help! I changed the rear pads without difficulty by using the screwdriver between the old pad and the rotor method, with the cap on the brake fluid reservoir slightly off to prevent build-up of pressure. Worked great. No problem getting the new pad and shim in. Took in total about 45 min. There is apparently a device which is like a pair of pliers that one can use to compress the piston, with the device having one clamp that is inserted over the piston and the other clamp over the outside of the caliper, but this screwdriver method seems perfectly sufficient.

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