Sticking Piston on Hope Mini

T1berious

Hi,

I've got an issue with a Hope Mini disk brake. The piston on the right hand side just isn't moving and I'm wondering what's the best way to go about fixing it.

Would I be better off just rubbing some alcohol on the piston after forcing it out by keeping pressure on the left hand piston? Or should I bite the bullet and just order new pistons and seals and just accept that I'm going to have to take the calliper apart?

It's the rear brake but as I've just upgraded the hoses it sort of makes sense to get this sorted.

Cheers for your advice.

T1b

ride_whenever

hopes are easy, the best bet would be to pull the piston apart, clean it and reassemble, then order replacement parts if they're needed.

stu8975

Try keeping the L/H piston/pad pressed in while you pull the brake and see if it un-sticks it, sometimes works. If not, as suggested, strip and clean.

shm_uk

Sounds like your best option is to remove the piston & give things a clean.

If the piston surface is dirty/damaged then a quick rub with some very fine wet-and-dry paper (wet) can help refurbish it.

It's highly unlikely you'd need to replace the piston unless it's badly damaged.

Probably worth ordering a seal kit (only a few quid) and replacing the seals whilst you've got it in pieces ...

ride_whenever

shm_uk wrote:

Sounds like your best option is to remove the piston & give things a clean.

If the piston surface is dirty/damaged then a quick rub with some very fine wet-and-dry paper (wet) can help refurbish it.

It's highly unlikely you'd need to replace the piston unless it's badly damaged.

Probably worth ordering a seal kit (only a few quid) and replacing the seals whilst you've got it in pieces ...

Do you mean the face of the piston? I hope you're not suggesting someone sands down their pistons to stop sticking, that's a recipe for disaster!

T1berious

Hmm, I think I'll order the parts and just be resolved to striping the calliper. I'd imagine it's fairly messy? Or do you bleed all the fluid out before opening up the calliper?

Thank you for replying

shm_uk

T1berious wrote:

Hmm, I think I'll order the parts and just be resolved to striping the calliper. I'd imagine it's fairly messy? Or do you bleed all the fluid out before opening up the calliper?

Thank you for replying

No need to bleed all the fluid from the system.

I would unbolt the hose from the caliper & use something to temporarily seal the end of the hose connector. A small amount of fluid will escape, but better than losing the whole lot. (I tend to find that as long as you don't pull the brake lever whilst the caliper's off the fluid stays in the hose by itself).

When you pop the piston out you'll lose some of the fluid from the caliper though.

Whatever you do, it'll all need re-bleeding once you've put it all back together.

shm_uk

ride_whenever wrote:

shm_uk wrote:

Sounds like your best option is to remove the piston & give things a clean.

If the piston surface is dirty/damaged then a quick rub with some very fine wet-and-dry paper (wet) can help refurbish it.

It's highly unlikely you'd need to replace the piston unless it's badly damaged.

Probably worth ordering a seal kit (only a few quid) and replacing the seals whilst you've got it in pieces ...

Do you mean the face of the piston? I hope you're not suggesting someone sands down their pistons to stop sticking, that's a recipe for disaster!

No, just go over it carefully with some very very fine paper to remove any blemishes from the surface that could cause it to stick.

This technique was recommended to me by someone else on this forum, and worked a treat. It doesn't remove any noticeable or significant material from the piston itself.

Northwind

Yup, perfectly reasonable, you want to be very careful with coated pistons but the idea is to remove the stubborn crap, not to sand down the piston. Fine wet and dry isn't aggressive, you don't want to go at it with 400 grit though Scotchbrite pad works too. Generally a last ditch but if the piston's going in the bin otherwise there's no great loss if it doesn't work.

There's various fixes you can try and do, just cleaning the pistons and seals (and seal gutters) will sometimes work, just cleaning without dismantling and applying a wee bit of appropriate lube to the seals (ie brake fluid or red rubber grease, or some say silicon spray) can help but in my experience it's a band-aid not a fix.

T1berious

Hi,

I'm really after the fix as this looks like the beginning of a trend with the rear brake. I've ordered the piston and seals so I'm just going to bite the bullet and take the calliper off, take it apart and replace the pistons and seals and hope it all comes out OK.

I think I saw a video on the web on stripping the calliper It's going to be a case of getting the rubber gloves on and making with the isopropyl alcohol.

Cheers for the replies

I'll let you know how I get on.

Many thanks,

T1b

ride_whenever

It can be messy, you cannot really get the fluid out beforehand unfortunately.

Which piston is sticking, because there are a variety of approaches based on which one it is...

allthegearnoidea

when mine stuck i sprayed in some brake cleaner and gave a little scrub with a stiff bristled brush (small spark plug one just about fits) and then applied some pressure to the working one and kept pulling the leaver until it moved! took a few pumps mind (you can poke an allen key in through the top hole and hold it on the bottom with it still mounted on the frame to help stop the moving piston from doing so!) then a light lube when it moved and pushed bac in and repeated until smooth!

stu8975

applied some pressure to the working one and kept pulling the leaver until it moved!

Already suggested, but seems he'd rather spend money on new piston before he's even tried, especially as its normally just crap build up that sticks the piston.

T1berious

The brake in question hasn't had much love over the last 5 years, so now seems as good a time as any to sort it.

I kind of have a it's brakes sort it out mentality and for £10 is it really worth cutting corners when it comes to safety?

So yeah, I'd rather spend a little now than see my partner at the bottom of the trail busted and bruised due to being unable to stop.

£10 piston and seals, cheap at half the price

but seems he'd rather spend money on new piston

Yep as the Mrs is worth more than a few beers, there's tight and then there's silly.

stu8975

You're forgetting you have STUCK piston, how exactly do you intend to get it out so you can replace it with the new one? Yep thats right, hold the working one in and squeeze the lever until (if) it moves.

T1berious

After getting the parts from the ever useful CRC, I took loosened the sticky piston by holding down the working one, got some brake fluid applied to the sticky piston. Once I'd got it moving I removed the calliper and disassembled it. It was pretty mucky, removed the old seals and old pistons, gave it a really good clean with IPA (Thank you Maplin), with a small coat of brake fluid replaced the seals and pistons. reassembled calliper gave it another clean with IPA, left it a bit and then bled the system.

Rear brake now as smooth as you like

Thanks for all the advice and I can safely say it wasn't as mucky as I thought it was going to be.

Cheers

T1b