Hi, due to some hamfisted mechanicing last night I have cracked a piston in my e4 brake.

My pliers slipped and took a chunk out of one of the pistons when I pushed it back after lubing it.

Can I just buy one piston, or do I need to rebuild the caliper? It’s two years old and has been fine until the pistons started to stick.

O_o

Just buy a piston and seal kit. You could get away with just a piston, but as you have to bleed anyway, and they were going you bother, you might as well renew all the seals.

One of the best things about Hope stuff if that you can actually get small parts for them.

They’re sold individually or as a full kit. Personally, I’d do all 4 pistons and seals if you’re doing any – otherwise you’re likely to get 3 slightly stubborn and one decent piston

You could also send to hope for repair. Not a cheap option but if you price all pistons + seals and your time it may be worth it as you get back a fully refurbished brake. From memory you also get a new set of pads.

You can change them without the bore cap tool with care, needle nose pliers, cable ties and a big syringe to blow them out of the caliper. Tricky thing is renewing the piston seal but gentle application of a very small flat blade screwdriver helps here.

You push your pistons back in with plyers? 😜

I have a proper tool for this but never use it. I’ve found an old plastic tyre lever I bent getting tyres on actually works best.

Out of interest, what do other people use?

Anything to hand, but I leave an old set of backing plate in to protect the pistons.

I also have a park piston tool, but not actually used it yet.

I had a cheap Draper margin trowel 3 piece set from toolstation £6, chopped down the biggest one with an angle grinder to the same width as an E4 pad, looks like a genuine piston retractor tool, made my mate one too with the 2nd biggest trowel, but a piece of smooth planed wood from B&Q would do, wouldn’t put pliers near my pistons.

I’ve always used Pedros tyre levers, work well.

Out of curiosity, how easy a job is swapping pistons and seals?

Fairly easy. You really need the bore cap tool. Use the brake to pump the inner pistons out.

I also use Pedros tyre levers.

There’s a good video in YouTube showing you the correct process too so you don’t end up with one piston being inaccessible.

Don’t use a screwdriver to seat the seals. A cocktail stick is much better and will reduce the likelihood of pinching and wrecking a new seal.

I did the seal and piston replace recently, its a really satisfying job. Bought the tool, just ordered more seals and pistons do I cam do it again.

Or just go to a your local cheap tat warehouse/pound shop and get some AmTech probes. Less than a tenner and makes life considerably easier than using screwdrivers or bent spokes and you won’t scrape the brake body to buggery (no wonder so many brakes end up “useless”)

And yes, buy the bore cap tool, you only need one size anyway. The cap can get stuck in with muck and a set of pliers are just going to shread it.

Don’t see the need to change more than the piston, the seal is probably best practice (get spares anyway in case you shred one getting it out) but as long as the pistons are all clean they should all work fine.

Thanks for the suggestions.

In my defence it suggests using pliers in a video from hope.

I won’t be doing that again!

I’ve already got a bore cap tool. I’ll sort myself a set of pistons and do the seals while I’m at it

Cheers, Martin

I need to replace a piston in my E4s as well. Can anyone recommend where to get borecap tool n parts from that will ship to New Zealand please?

@Brainflex, I think I got mine from Biketart but lots of the UK online shops sell them at roughly the same price, Chain Reaction must ship to NZ.

Anyone rebuilt a Tech3 lever? Been meaning to do mine for ages.

@Martin – I have done the exact same thing. Except I got all ham fisted with a large screw driver.

I was intending to get the LBS to rebuild the brake for me. The brakes have been sticking for a while and I was trying to lube up the pistons.