Hope V4 ( or possibly all calipers ) expert advice required

My V4 front brake caliper has become sticky/stuck and will not return to allow the wheel to turn. I can lever the pistons back but if  I use the brake its back stuck . I have taken it apart and lubed up the pistons.

Cleaning inside I can feel a tiny bit metal or similar, should they not be smooth inside, can they be sanded or something to make them smooth again?

Email Johnny at Hope: service@hopetech.com

What did the pistons look like when they came out? I’d wager they need new seals and possibly a piston or two.

I think Hope do a fixed price ‘service’ where you send it to them, which could work out a decent option if they’re likely to need multiple pistons.

They’re not ‘fit and forget’?

Am considering Tech4/V4 for a new bike next year.

How much TLC do they need?

No more than any other brake.  I have a variety of hope brakes.  they used to get annual oil change.  I replaced one seal that blew and I bust a piston in one being clumsy

Hopes rebuild service is very good

to the OP – no there should not be a shard of metal there

All four pistons look ok, I will email Hope about service costs.

I have down zero maintenance in over 4 years ? apart from changing the pads and a re-bleed when running the rear hose through my new frame.

As of Sept 2023 –

We charge £60 per brake plus p+p for a service on a 4 piston brake (the complete brake, master cylinder and caliper). All seals and pistons are replaced, then the brake is bled and new pads fitted.

If you consider pads are about 20 quid a throw, it makes the rest of it pretty damn economical as it’s effectively replacing all the internal gubbings for £40

I’d guess that the issue is a build up of dirt on the pistons, or you’ve used something that has caused the seals to swell.

The phenolic pistons eventually get a layer of dirt building up on them, which will cause them to stick. You can clean them in situ by pumping them out one at a time, dribbling a little brake fluid on to them, and wiping them with a bit paper towel (I usually wrap a bit paper towel around a flat screwdriver, so I can wipe all around the piston). Then dribble a bit more brake fluid over the piston and pump it back in. I usually repeat it at least a couple times per piston.

You should only ever use DOT fluid, or silicon near the pistons. If you’ve ever used something like GT85/WD40, then chances are the seals have swelled, and no amount of cleaning will cure the problem.

Personally, I’d buy a seal kit and a set of the new stainless pistons, however for the cost of a hope service, unless you really like fixing your own stuff, it’s probably just as cheap to pay for the Hope service.

I’ve just done a quick check on the prices, and for a V4 caliper, it’s nearly £40 retail for new pistons and seals just for one caliper, and that’s without the bore cap tools (although with a V4, IIRC there is enough room to get the pistons out through the pad slot)

Service seems like a very good deal- with the brake back working as expected which may not be the case if i do the service?

I bought a handy 3D printed tool that allows one piston at a time to come out. Cleaned them and used the Hunter silicone There was loads of dirt on them. If I get them serviced I now have the tools to look after them now.

How much TLC do they need?

No more than any other brake. The difference being you can actually get every single part, and rebuild them (or get Hope to do it for a very reasonable cost).