New Pads In, Different Feel? - PeachParts Mercedes-Benz Forum

Ara T. · #1 10-26-2005, 08:33 PM

After getting my new master cylinder installed and getting a decent firm pedal (a bit too firm, I think my booster is dying) I decided to do my first brake pad job... I installed some of those PBR Ceramic Ultimate Pads all around. It was pretty simple and would have been a joy to do if I didnt have to use that sticky anti-squeal paste. Im not sure what brand the old pads were (they were not MB ones) but they seem very smooth compared to the rough feel of the new PBR pads. Anyone felt really smooth brake pads before? Or is that what youd call glazed pads?

The problem is im getting a rather mushy ineffective brake pedal now with the new pads, I did break them in by doing 45-0 mph with little to medium brake pressure at least 15 times. The only thing I can think of is that when I had the brake reservoir cap off, I pushed the brake pedal maybe 6 or 7 times to set the pistons against the pads. Perhaps this drew air into the MC or something? I really dont want to pull the MC off again to bleed it, I am really really sick of brake fluid. Anyone had experience with this? I did bleed the brakes at the caliper after doing the pads, but saw no bubbles or anythin comin out.

SD Blue · #2 10-26-2005, 09:51 PM

Quote:

Originally Posted by Ara T.

.... The only thing I can think of is that when I had the brake reservoir cap off, I pushed the brake pedal maybe 6 or 7 times to set the pistons against the pads. Perhaps this drew air .............?

This sounds like air in the system, especially "6 or 7 times". However, you should bleed it with the master cylinder in place. http://www.peachparts.com/shopforum/showthread.php?t=117258&highlight=homemade+pressure+bleeder this little project should alleviate that "sick of brake fluid" feeling.

boneheaddoctor · #3 10-26-2005, 09:51 PM

You have to bleed the M/C with it on the car not off as a system at the calipers...read what you wrote again and correct it or did I read it right?

Maybe you did not bleed it enough....remember you will have to effectively to a total fluid transfer to run any bubles completely through the system...and thats more than a few squirts.

Glinko · #4 10-26-2005, 09:53 PM

Yeah, I am having the same exact problem. I installed new rear calipers/pads, and the pedal is mushy.

Ara T. · #5 10-26-2005, 09:57 PM

Quote:

Originally Posted by boneheaddoctor

You have to bleed the M/C with it on the car not off as a system at the calipers...read what you wrote again and correct it or did I read it right?

Maybe you did not bleed it enough....remember you will have to effectively to a total fluid transfer to run any bubles completely through the system...and thats more than a few squirts.

Before installing the new MC I did a bench bleed. After installing it I did a bleed with the MC in place, at each wheel... the pedal was fine, then I changed pads and I got a crap pedal instead of a brake pedal now. I bled a good amount as well... the container is about the size of one of those advil containers and I did one full container per wheel. I will keep trying though... if i keep at this im gonna clean Kragen out of their DOT4 fluid.

boneheaddoctor · #6 10-26-2005, 09:59 PM

Quote:

Originally Posted by Ara T.

Before installing the new MC I did a bench bleed. After installing it I did a bleed with the MC in place, at each wheel... the pedal was fine, then I changed pads and I got a crap pedal instead of a brake pedal now.

maybe there was still a bubble in the system...different pads with affect grab differently ( depending on material and coefficient of friction) but should not account for mushy pedal.

I have had that happen to me...sometimes you need to move more fluid to purge it than you think.

t walgamuth · #7 10-26-2005, 10:00 PM

pads may seat and feel better in a few days of driving.
you are stopping ok right?

tom w

boneheaddoctor · #8 10-26-2005, 10:02 PM

Quote:

Originally Posted by t walgamuth

pads may seat and feel better in a few days of driving.
you are stopping ok right?

tom w

I think he needs to better describe what he feels...new pads won't grab well until they are broken in completely...however new pads should never cause mushy pedal.

Ara T. · #9 10-26-2005, 10:09 PM

Okay, try this: I have to push the brake pedal further with the new pads than I did with the old ones, or at least it seems so. I don't think id stop very well in a panic situation, I haven't tried a hard stop yet, I want to break these pads in right.

As an aside, anyone who hasnt should do sway bar bushings on their W123... the car feels so much better in curves, doesnt feel like a cadillac from the 70's anymore. I can't imagine how nice these cars must have felt when brand new.

boneheaddoctor · #10 10-26-2005, 10:13 PM

Quote:

Originally Posted by Ara T.

Okay, try this: I have to push the brake pedal further with the new pads than I did with the old ones, or at least it seems so. I don't think id stop very well in a panic situation, I haven't tried a hard stop yet, I want to break these pads in right.

As an aside, anyone who hasnt should do sway bar bushings on their W123... the car feels so much better in curves, doesnt feel like a cadillac from the 70's anymore. I can't imagine how nice these cars must have felt when brand new.

Sounds like you need to give it a few hundred miles to fully break in...and its possible they just won't grab as well as the old compound.....

All pads and compounds are not equal......thats why I replace my brakes in complete sets.....even though they don't wear equally...wasteful maybe...but I like the knowledge all brakes run the same material and will be better balanced.

Point of note....long life pads tend to be crappy since they sacrafice agressivness for low wear...the two really are mutually exclusive. THats based on 30+ years of doing my own brakes...

Ara T. · #11 10-26-2005, 10:21 PM

Should I continue being real easy on the pads then?

boneheaddoctor · #12 10-26-2005, 10:23 PM

Quote:

Originally Posted by Ara T.

Should I continue being real easy on the pads then?

slow easy stops for about 100 miles or so..(not highway miles either) so you don't glaze them. (they outgas binders during this time)...if you drive mostly highway up that to about 300 miles...

Ara T. · #13 10-26-2005, 10:50 PM

Regarding glazing, is that what I saw with the old pads? That smooth shiny pad surface?

#14 10-26-2005, 11:25 PM

Pads are generally rather hazy looking...its just their nature.

I have the PBR Delux models on my car (not my first choice but dad got them for me).

They work good after you abuse them a little (after they are broken in).

I have about 8k on mine and they are doing okay. Probably over 50% left...I drive hard

I think my last pads were mercedes brand....these new ones are not quite a nice but they dust very little. THey get better with time...just bleed your brakes and hold out for awhile

t walgamuth · #15 10-26-2005, 11:36 PM

to break in pads. i know you are supposed to but i never think of it. i am not particularly hard on them.

i think that new pads can affect pedal feel til they are conformed to your rotors. they might be a little off on the angle of attack. i think that would affect feel.

did you turn or replace the rotors or just do the pads?

if in doubt the above rec to bleed the calipers is not a bad idea.

tom w