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Discussion Starter · #1 ·
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":rolleyes:
 

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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":rolleyes:

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
 

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

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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...
 

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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":rolleyes:

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...
 

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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.
 

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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.
 

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if you were able to get the piston all the way into the caliper (i.e. not frozen), check the thickness of the new pads. Depending on whose pads you bought, they may be a bit too thick.
 

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You sure you have the right pads part nos. and right rotors? As others pointed out, there is no magic to compressing the piston and you don't need extraordinary force (such as prying with breaker bar). On some cars, the pistons come out stepwise such that you need to rotate the pistons back in with a special tool, but not the M5 calipers. Just need C clamp or spreader tool. I had Axxis D+ pads on my car (recently changed to Centrics), and it was an easy job.
 

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Discussion Starter · #18 · (Edited)
You sure you have the right pads part nos. and right rotors? As others pointed out, there is no magic to compressing the piston and you don't need extraordinary force (such as prying with breaker bar). On some cars, the pistons come out stepwise such that you need to rotate the pistons back in with a special tool, but not the M5 calipers. Just need C clamp or spreader tool. I had Axxis D+ pads on my car (recently changed to Centrics), and it was an easy job.
Thanks Guys;

Yes - cap was off.
Tried the C clamp as well.
OEM rotors & Axxis pads for this car (completed the fronts with Axxis recently - no problem in retracting calipers).

It's probably this particular caliper - as in frozen?
Anyone have a low mileage drivers' side for sale? :)
 

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Vics:

If the piston is all the way in, flush with the caliper side, and the pads still don't fit, then the pads are wrong.

If you moved the piston it aint frozen. Again that would point to the pads.
 

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Did it move at all? It would be unusual for it to move some and just stop. The piston should depress flush into the caliper...maybe you pressed it in at an angle and it got hung. you may want to put it back on with a piece of wood in between and press the brake pedal a time or two and see if it frees up.
 
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