Replacing brake pads - back wheel virtually locked

[alpertonian]

Changing the rear brake pads should be easy eh?

Changing the pads on my wife's F800R
The R clip and retaining pin come out fine, the piston retracts fine, and I can compress the caliper so that I can fit in the brake pad behind the disc, but it is so tight when you release the compression of the caliper, that the back wheel is virtually locked.
The other pad in front of the disc has plenty of space

The pads are identically shaped, with the only difference being the thickness of the new ones, as there's no wear. I've fitted both new pads and got pedal pressure back, but the "rear" of the two pads is still so tight, and locking the wheel even with caliper still pushed in.

When I put the old thinner pads back in everything works fine.

Am I missing some sort of adjustment which would centralise the brake disc in the gap between the two pads?
Thanks in advance

[Tango13]

Does the bike have ABS? On some cars with ABS fitted the piston need to be wound back with special tools, not just pushed back into the caliper. Also did you remove the reservoir cap before pushing the piston back?

[alpertonian]

Yes and Yes.

It's odd though that even with the piston fully pushed in, just fitting one new brake pad and the wheel won't spin.

[Jazoli]

Have you removed the caliper and lubricated the sliders?

Edited by Jazoli on Thursday 24th September 16:45

[alpertonian]

Not yet, But the piston seems to be working ok. The wheel is locked when just the new pad that does not come into contact with the piston is put in place

[Steve Bass]

alpertonian said:

Not yet, But the piston seems to be working ok. The wheel is locked when just the new pad that does not come into contact with the piston is put in place

Are these orignal/OEM or aftermarket pads? Decent brand or chinese cheapies....??

Sounds like the pads are over thick which is causing the binding.

[Prof Prolapse]

Not wishing to question your competence, but is it definitely pushed back in all the way?

[Krikkit]

Steve Bass said:

alpertonian said:

Not yet, But the piston seems to be working ok. The wheel is locked when just the new pad that does not come into contact with the piston is put in place

Are these orignal/OEM or aftermarket pads? Decent brand or chinese cheapies....??

Sounds like the pads are over thick which is causing the binding.

I've had this same issue with aftermarket pads.

In one case I sanded the coating on the back of the pad down as it was ridiculously thick. In another it was just about touching the disk, and wore itself down on the test drive to allow enough clearance.

[_Neal_]

Steve Bass said:

Are these orignal/OEM or aftermarket pads? Decent brand or chinese cheapies....??

Sounds like the pads are over thick which is causing the binding.

Sounds like this to me. Although perhaps take the rear wheel off/unbolt the caliper from the bike (which it sounds like you haven't done yet) and take look at it for any issues/anything you've missed.

[alpertonian]

Prof Prolapse said:

Not wishing to question your competence, but is it definitely pushed back in all the way?

Happy to have my competence questioned. The piston is definitely 100% all the way back. Its the pad that is not in contact with the piston that dos not have the space, even when the piston is pushed back, so it sounds like they are too thick.

EBC brake pads so not cheapos.

[alpertonian]

_Neal_ said:

Sounds like this to me. Although perhaps take the rear wheel off/unbolt the caliper from the bike (which it sounds like you haven't done yet) and take look at it for any issues/anything you've missed.

Think this is my next step...

[gdr]

If it's a single piston floating caliper, and one pad is loose while the other is tight, sounds like the caliper is being prevented from centering with the new pads in. The new full thickness pad on the non-piston side would be the tight one in that case even if piston is fully retracted. Need to clean up and lubricate the slider pins.

[V8RX7]

gdr said:

Need to clean up and lubricate the slider pins.

^^^ This is my guess too

OP without any pads does the caliper move in and out on the sliders ?

[crofty1984]

V8RX7 said:

gdr said:

Need to clean up and lubricate the slider pins.

^^^ This is my guess too

OP without any pads does the caliper move in and out on the sliders ?

Sounds like a good place to look.

[alpertonian]

Thanks. Almost certain it's my sliding pins causing the issue as it's seized. Might also explain a bit of uneven wear on the old pads.

Next to try and get it moving

Thanks all

[trickywoo]

I think it’s because BMW.

You probably have to code the new pads to the ecu or something equally ridiculous.

I’m only half joking btw.

[alpertonian]

V8RX7 said:

^^^ This is my guess too

OP without any pads does the caliper move in and out on the sliders ?

No. They don't. Eliminated everything else so it has to be the sliding pins are stuck.

BMW bikes can be a bit of a pain!

[Biker's Nemesis]

Has the fluid been changed recently ie while the pads were worn down?

Is the fluid level right at the top of the MC reservoir?

[Prof Prolapse]

Poor bd.

This is one of those classic, "I'll change them myself in ten minutes" type jobs that turns into four hours of asking the internet.

[Jazoli]

alpertonian said:

No. They don't. Eliminated everything else so it has to be the sliding pins are stuck.

BMW bikes can be a bit of a pain!

All bikes need maintenance, not just BMW's, clean them up with some wire wool and give them a light smear of grease