I have a very efficient Hope Mono 6 rear disc brake which is normally no problem but recently I decided to replace the pads and the right hand piston refuses to retract, thus making insertion of new pads impossible. I've tried using a tyre lever, flat tools etc, but it refuses to budge. Any ideas?
See attached photo
Cheers
Hope Disc Brake
Re: Hope Disc Brake
It is possibly siezed which could require a stripdown/clean rebuild.
Firstly.
Have you tried putting the old pads in then trying to pry it back.
Try opening the bleed valve slightly then try to pry it back.
Try cleaning the piston and rubbing a bit of Brake fluid on the protruding surface.
Sometimes it's just stuck and requires a "bit of persuasion".If all else fails it could be a stripdown job.Not particularly hard but can be messy!
Firstly.
Have you tried putting the old pads in then trying to pry it back.
Try opening the bleed valve slightly then try to pry it back.
Try cleaning the piston and rubbing a bit of Brake fluid on the protruding surface.
Sometimes it's just stuck and requires a "bit of persuasion".If all else fails it could be a stripdown job.Not particularly hard but can be messy!
Re: Hope Disc Brake
Best thing to do is restrain the piston that moves and get the stuck side moving using the brake lever. If it moves forward it'll usually move backward.
I use two plastic tyre levers with holes drilled in them - tyre lever one goes in the caliper, tyre lever two goes outside the caliper, they get bolted together to hold the free piston back. Pump the lever till the stuck piston moves, clean the ring of crud from the piston, carefully push stuck piston back. It's possible for the piston to go in crooked and bind. Good luck!
I use two plastic tyre levers with holes drilled in them - tyre lever one goes in the caliper, tyre lever two goes outside the caliper, they get bolted together to hold the free piston back. Pump the lever till the stuck piston moves, clean the ring of crud from the piston, carefully push stuck piston back. It's possible for the piston to go in crooked and bind. Good luck!
Re: Hope Disc Brake
I agree with Andy's suggestion.
In addition to this I note that
- a small G-clamp can often be used to push the piston back (but there isn't much benefit in pushing it back if it won't also push out...)
- Hope recommend that you use a Silicone spray lube on the pistons; possibly lack of this has helped cause the piston stickiness...?
NB Brake pistons won't move easily if they are even slightly cocked in the bore; they must be pushed back exactly square.
cheers
In addition to this I note that
- a small G-clamp can often be used to push the piston back (but there isn't much benefit in pushing it back if it won't also push out...)
- Hope recommend that you use a Silicone spray lube on the pistons; possibly lack of this has helped cause the piston stickiness...?
NB Brake pistons won't move easily if they are even slightly cocked in the bore; they must be pushed back exactly square.
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: Hope Disc Brake
Hi all,
Thanks for advice. I'll get out in the bike shed and try again. It's on a tandem so might have to call on stoker to help. Did try inserting old pads but without success, also dabbed some alcohol on exposed areas to clean/loosen.
Thanks for advice. I'll get out in the bike shed and try again. It's on a tandem so might have to call on stoker to help. Did try inserting old pads but without success, also dabbed some alcohol on exposed areas to clean/loosen.
Re: Hope Disc Brake
Update on jammed piston - I coated pistons liberally with Famous Grouse (only a miniature bottle, so not too much wastage!) and disc brake cleaner then inserted the plastic handles of two cone spanners in the gap between said pistons and wiggled them. This resulted in sufficient retraction to enable old pads to be inserted, so am now back to square one. New pads are on the way which I may or may not fit, as brake does now work as before. Thanks for responses from forum members. I live in Bualnaluib, sixty seven or so miles from nearest bike shop.
Re: Hope Disc Brake
Hope have a video showing how to lubricate the pistons on their brakes: https://vimeo.com/67723111.
Re: Hope Disc Brake
Thanks, NickJP. It is a good video. Silicone grease ordered.