rear caliper movement

My rear brake is binding slightly. I can move the wheel with light hand pressure but it doesn't spin freely like my other bikes and I can hear the pads rubbing. I have freed up the pistons and the seals/ grooves are all fine. I noticed when replacing the caliper that before the pad s were in there was a fair bit of movement possible of the caliper twisting/ rocking it between the pins ie not just the sliding along they are designed for. When the pads are in and up to the disc in the normal position it is still possible to detect some movement of the caliper twisting it on the pins it by hand. This doesn't seem right because every time the brakes are applied there is a slack to be taken up which would cause wear. the pins are like new but I am wondering if the caliper body internal bore has worn. There is no damage to the caliper pin boots. It would be strange to wear at such a low mileage 8k. Possibly an oem fault or since it was fine when new something in the mounting plate is out of alignment causing the caliper to wear prematurely. Can anyone else twist/rock their rear caliper? I am going to have the bike looked at by my dealer in 10 days but interested in views ahead of this .
cheers
David

have you checked the level in the master reservior?it could be overfull after the pad change,the caliper on my 4500 mile bike rocks a bit on the sliders as well.

No Help I suppose but my 1250 mile bike has movement too. Could this be to allow for any run out on discs warping etc but still allow safe operation.

Don't forget its a shaft drive and therefore you're turning more with your hand than on a chain drive bike. Its normal to hear and feel a slight pad noise as you rotate the wheel as they "rest" on the disc without pressure but it shouldn't be more than that and certainly not binding. Its also not a floating disc as found on the front.

My rear pads just rest on the disc , you can hear the slight squeak as you push the bike, it's not an issue That's a 2009

By coincidence I just serviced my bike and noticed the same problem with my rear brake caliper binding.

I used a small G clamp to hold each piston in turn whilst operating the pedal to extend the other piston out of its bore for cleaning. The 'rearmost' piston was quite tight in the bore and did not retract slightly when the pedal was released, thus causing the binding. Obviously the rearmost piston collects all the road crap around the piston skirt from the action of the rear wheel rotating. By spraying with brake cleaner and moving the piston in/out repeatedly plus a scrub with an old toothbrush I got it moving freely enough to retract slightly when the brake pedal is released. The dirt on the piston was almost microscopic and difficult to see against the grey piston colour yet it was enough to cause the binding. I also changed the brake fluid front and rear although it was clear and free of dirt.

I can now spin the rear wheel without any brake rubbing or binding and the calliper works smoothly when used.

Perhaps you could inspect the movement of your rear calliper pistons closely, looking for a tiny retracting motion when the pedal is released meaning your pads are releasing from the disk properly. If not, clamp each piston individually whilst pumping out and cleaning the other.

I can twist/rock my rear calliper which is typical of these bikes as the cantilever effect of the single leading sliding pin allows the calliper to move a bit on the pin. Its worth separating the carrier and calliper and cleaning and lubricating the sliding pin beneath the rubber boot.

Hope this helps.

if the brake isnt getting hot when moving you may want to drop the driveshaft out to check the U/J isnt starting to seize.as this can make the wheel hard to turn by hand.
mike

I've been doing the same piston free-off as Pukmeister for years and it works. Keeps everything working nicely and avoids rubbing.

When I was looking at GSs to buy I did see a demo bike with hardly any miles that had quite a lip on the outer edge of the rear disc- excessive wear caused by rubbing?

Thanks for the replies.

I have had the pistons/ seals out and checked there is nothing on the pistons or seals or in the grooves. Will definitely try draining a little from the master cylinder. from the comments above it seems some movement is usual on a new caliper so maybe I am worrying excessively about that. Is the slight rubbing as opposed to binding normal ? If you put your foot on your wheel and drag it down hard how much does it spin ? Not much more than a half a spin on my Gs versus 2 or 3 completely free spins on my other shaft drive bike ( pan ).

davnjud said:

If you put your foot on your wheel and drag it down hard how much does it spin ? Not much more than a half a spin on my GS

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About the same on my GSA but you can feel the difference once you free a previously sticking rear brake.

davnjud said:

Thanks for the replies.

I have had the pistons/ seals out and checked there is nothing on the pistons or seals or in the grooves. Will definitely try draining a little from the master cylinder. from the comments above it seems some movement is usual on a new caliper so maybe I am worrying excessively about that. Is the slight rubbing as opposed to binding normal ? If you put your foot on your wheel and drag it down hard how much does it spin ? Not much more than a half a spin on my Gs versus 2 or 3 completely free spins on my other shaft drive bike ( pan ).

Click to expand...

If you're not sure, take the caliper off and then spin the wheel. Or just loosen the two bolts, rock the caliper from side to side a bit to push the pads back then spin the wheel.

Beemerman59 said:

If you're not sure, take the caliper off and then spin the wheel. Or just loosen the two bolts, rock the caliper from side to side a bit to push the pads back then spin the wheel.

Click to expand...

Thanks Beemerman, good idea -will try this when I get home later today

The rear caliper is easy to strip & rebuild and new seals are only £18. Why put up with a sticky brake when a proper fix isn't hard to do.


Sent from a widget that can't spell.

Well the strip and rebuild of the caliper had definitely helped with the slight binding and the wheel now rotates almost a full turn when spun. The resistance is coming from the shaft drive and not the pads as I discovered when trying to spin with the caliper off. Interesting that there is much more resistance than on a Honda Pan shaft drive - obviously a different design issue. Still not completely happy with the feel of the brake so will up date on dealer findings on Monday.

Bled it to death and realised on my way to the dealer that it really is ok which they confirmed setting my mind at rest. They also confirmed that the quite significant rocking movement on the pins you can feel with the pads out is normal. ( all at no charge Alan Jefferies) I have ridden 7 different bikes in the last week and got a good feel for how different rear brakes perform including linked systems. ( Abs and standard pan, cb 750 four, Honda crossover, New RT, Triumph Trophy, GSA. ) and my GSA is up with the best. Despite my earlier finding that exercising the pistons fully in and out with the caliper off significantly improved binding it was only completely eliminated by doing a pistons out service as recommended by Bendy toy above. I couldn't see any debris in the seal groove or damage to the seals but it seems they are very sensitive to even tiny contamination. Any way I now have good working brakes and my rear wheel can be spun over one full turn. Interesting to see quite wide variation in the rear pads binding of the 5 used bikes I managed to check in the dealer showroom including one totally bound. That 's about it on this mini saga - thanks for reading.

See also this post if you are considering a rear caliper strip

http://www.ukgser.com/forums/showth...200-rear-brake-overhaul&p=3804882#post3804882