Hi all, front brake calipers appear to have a couple of pistons that can’t be arsed to move. Liberally sprayed with brake cleaner and tried to pursuad with pliers but not moving. Is it easier to buy new calipers or should I overhaul them? I’m not that able in the garage but get by. Any guidance would be appreciated.
As long as your comfortable bleeding them back up and can be confident in your work then there’s no reason why you can’t refurbish them yourself and it will probably be cheaper than sourcing another pair that could well have the very same issue as yours. Basically, you need to remove and split them. Straight forward enough. Next would be piston removal. An air line or even a pump would really help things along here. They shouldn’t require much pressure to get them out. A good clean up of the whole calliper including pistons, new seals ( relatively cheap ) install and reassemble. The seal kits are comprehensive and includes everything you will need. Back on( new pads be nice), bleed up. Now these are obviously crucial to safety so unless your happy to do them yourself just ask a competent mate.
You can sometimes get stuck pistons moving if you jam all the others back so only one can move at a time. Leave one caliper on the disk while you work on the other. cut a block of wood that fits between two opposing pistons when they're both pushed in. Use a 2" G-clamp to hold back the piston opposite the stuck one(use a scrap of leather to avoid scratching the outside of the caliper with the clamp). Now the only piston that can move is the stuck one. If you get it snapped free and pumped out a bit you can clean it, smear a little red rubber grease round the piston, push in/pump out a few more times.... Sometimes you need to use a second G-clamp to push the piston back in again the first time or two(again - Use a scrap of leather to avoid scratching the outside of the caliper with the clamp). ...and sometimes that can be beyond footery. I used to use clamps like the red one on the left which would just about do the job but were always getting in each others way and falling off because I didn't have them positioned just so. Got a pair of the black Axminster ones just for cleaning and freeing pistons. The lack of bracing under the platform makes the job sooo much easier.
Take the bleed nipple out and put a grease nipple in and pump out with a grease gun, you get fantastic pressure with a grease gun and at a controlled and steady speed, it’s probably dirt or moisture got behind the dust seals and created a little corrosion around the main seals, powerhouse brakes in chesterfield probably do a rebuild kit for them.
Very easy to rebuild. You'll need a big old Torx bit to split the caliper halves (T22 I think, but I can check). I use TRW rebuild kits... comes with all the seals, new bleed nipples including caps, and even a little sachet of red rubber grease. If, as you suggest, some seals have gone and wedged against the pistons, then you'll probably need more than compressed air to remove them. I've done it VERY CAREFULLY using several layers of cloth and pliers (you don't want to mark the piston faces)... you twist and pull, rather than just pull... or you can splash the cash on proper piston pliers. You can take the opportunity to give the calipers a good clean... it's a very satisfying job. I took some pics when I last did mine: RR7 caliper rebuild | 1000RR - The CBR1000RR Fireblade Forum If anything the harder job is bleeding the front brakes after refitting the calipers.
Get a set of monobloc 2008/2009 calipers - they fitted straight on my 2007. Look better, don't seem to have as many issues. I got a really clean set for £90 - was easier and cheaper than refurb/painting
Thanks all, great replies and got some thinking to do now. I will report back. So grateful to you all
It’s hard to tell from the pictures as you can’t see the outside which is the important part, the hollow internal doesn’t matter If it has any corrosion s it’s not against the seals.
