Can't install rear pads - The Unofficial BMW M5 Messageboard (m5board.com)

vics · 10th March 2008, 04:37

OK, can't expand the piston in far enough to get the Axxis deluxe advanced pads around the rotors... Have ruined original pads & rotors with breaker bar which is ultimately OK as I've got new rotors as well - but had to button her back up & submit to temporary failure....

More than enough leverage with 2 foot bar- figured perhaps something with ABS? Started the car up, opened the bleed screw as well - NOTHING....

OK, tell me WTF I'm missing to get that additional 1/16th"

Blockdoc · 10th March 2008, 04:58

Quote:

Originally Posted by vics

OK, can't expand the piston in far enough to get the Axxis deluxe advanced pads around the rotors... Have ruined original pads & rotors with breaker bar which is ultimately OK as I've got new rotors as well - but had to button her back up & submit to temporary failure....

More than enough leverage with 2 foot bar- figured perhaps something with ABS? Started the car up, opened the bleed screw as well - NOTHING....

OK, tell me WTF I'm missing to get that additional 1/16th"

I'm curious too...since I will be tackling this myself in the near future. FWIW, the BMW TIS describes one of their many "special tools" to expand the piston.
Can this be done without the special tool?

Brian

M5CCIE · 10th March 2008, 05:23

I just used a regular pad spreader with the piston attached pad left in place to push the piston back. No issues.

Stika · 10th March 2008, 05:32

Did you try it with the reservoir cap off?

E55AMG2 · 10th March 2008, 05:37

any $5 brake piston tool can do the job in 30 seconds...the right tools make the job that much easier

kindanutz · 10th March 2008, 05:38

maybe the piston is frozed or the brake hose was twisted or colapsed... also you don't need a special tool to do bmw brakes... i wouldn't be able to diagnose the problem without more info or seeing it myself...

kindanutz · 10th March 2008, 05:39

Quote:

Originally Posted by E55AMG2

any $5 brake piston tool can do the job in 30 seconds...the right tools make the job that much easier

or a c-clamp, or large pair of channel lock plyers...

kindanutz · 10th March 2008, 05:46

Quote:

Originally Posted by vics

OK, can't expand the piston in far enough to get the Axxis deluxe advanced pads around the rotors... Have ruined original pads & rotors with breaker bar which is ultimately OK as I've got new rotors as well - but had to button her back up & submit to temporary failure....

More than enough leverage with 2 foot bar- figured perhaps something with ABS? Started the car up, opened the bleed screw as well - NOTHING....

OK, tell me WTF I'm missing to get that additional 1/16th"

i don't understand why you used a pry bar in the first place... a three pound sledge or an air hammer would have gotten it off without damaging the stoping surface... you could have easily gotten the job done without damaging the rotors... also when you opened the bleeder screw did you leave it open, so it could gravity bleed... there is also a possibility that now that you opened the bleeder you are going to have to bleed the brakes...

TCM · 10th March 2008, 05:51

Were the rear brakes draggin before swapping? You may have a frozen caliper piston or a busted seal. Have done countless M5 brake jobs and never ran into this issue. Usually piston slides right back with the proper tool. Please keep us updated.

jaj · 10th March 2008, 06:18

There's something wrong with the caliper - I've had mine apart probably 10 -12 times over the last five years and they're easy. If the piston won't go back in with leverage, then it's frozen in place (rusted, probably) and needs professional help.