Rear caliper

[Stedman8]

Hi all, I am having trouble with the rear brake caliper  pistons on my fazer once I free them and think its sorted they start binding again - it looks like a dismantle and thorough clean etc- but  just a quick question when looking at the caliper from behind the disc appears to sit well to the left of the slot in the caliper - it doesnt touch but is that the position its supposed to be in or should the disc sit in the centre of the slot,cheers Steve

[Dead Eye]

The discs are semi-floating (I think) so it shouldn't matter

[darrsi]

The discs are semi-floating (I think) so it shouldn't matter

Rear isn't?
It's about as floaty as the Titanic! 

[spamfritter]

my disc sits central .. 


i have just done strip and rebuild on rear caliper ,,it takes about an hour start to finish ..
 having done this job many many times i find that the sticking is always down to a build up behind the first small dust /dirt seal ....i pop out both seals ,,and clean them most times the rubber needs scraped wih your nail to remove deposits ,


,then scrape out the seal grove with ,, suitable tool ...i use a bit of sheet alloy cut to a point and then bent to a hook to allow access to the groove ,,, then wash out and clean caliper ...clean pistons ..i have wire brush mounted on bench grinder ... and ree assemble using clean break fluid as lube and your good to go ,,if seals are real bad leaking etc change them but most times a clean out is enough ..

[Stedman8]

Cheers spamfritter, thanks for those instructions I have new seals,but if the original seals are ok , should I put the new ones in as a matter of course or save them until needed. The way the disc is sitting in the caliper does puzzle me ( which isn't difficult  ) I wonder why that is, is there a spacer or similar that is missing ? Anyway stripping and cleaning is the first thing on the list,cheers Steve

[Dead Eye]

The discs are semi-floating (I think) so it shouldn't matter

Rear isn't?
It's about as floaty as the Titanic! 

Yeah, I questioned this in my head when I posted it but figured someone would correct me if I was wrong

[tosh23]

If the disc isnt sitting in the middle of the "groove" the look at your wheel alignment...

[limax2]

 The disc should be in the middle of the calliper slot. It is fixed by the calliper to carrier bracket fitting face, carrier to wheel spacer face, spacer to bearing, and position of bearing in hub. It is hard to see how any of these have become out of spec but I would start by checking the fitting faces of the calliper and carrier and correct length of spacer. If the wheel bearing on the disc side was not fully pushed in it would throw the disc to the left, but I think the bearing would soon have collapsed if that was the case. A longer spacer would also have the same effect.
Have you checked if the gap is the same front to back. i.e. is the calliper parallel to the disc in the line of travel.
I can't see how wheel alignment would effect the position of the disc relative to the calliper.

[Stedman8]

I did check the wheel alignment ( in a rudimentary fashion - nothing hi-tech ) and that seems ok, as for the rear axle ,everything seems to be in place,its as if there is a spacer missing or too short by a couple of mil, as an experiment I put a 2mil thick stainless steel washer between the disc and the wheel on every bolt and that centres it - although it wont be taken on the road with these on as I'm not sure how safe it would be  so please keep the help coming , I surely need it , cheers everyone,Steve

p.s. I have taken the caliper apart and totally cleaned it and the pistons etc will be putting it back later so hpefully this will sort out the seizing prob, as for the positioning of the disc  , later,Steve