Hope tech brake bleed advice

[ishaw]

I've done some work on a set of hope tech brakes. Fully serviced the levers and given the callipers a good clean and lube.

The bike I fitted them to is small, so hoses were shortened to suit, then the brakes were bled.

I got a good bleed done, all feels good but I suspect I didn't use a fat enough block between the pistons as the stick out s little and with pads fitted, are very close to the rotors and so impossible to align without rubbing.

My question is this. Can I simply remove the reservoir covers, push the pistons in, let the excess fluid spill out, refit the covers and solve the problem, or will I need a full bleed with a wider block between the pistons?

My logic is that there's slightly too much fluid in the system to allow the pistons to retract fully.

Thanks

 

[old_coyote_pedaller]

Instead of removing reservoir covers just crack open bleed nipple on caliper, put rag over it and push pistons back after removing pads.
That's what I've done in past when brakes have been previously bled with worn pads then when trying to fit new pads there's not enough clearance.

 

[Cloverleaf]

Yep, agreed; crack open the nipple while holding a rag over the end (tightly) and squeeze the lever. As with bleeding, don't release the lever until the nipple is tight!

 

[ishaw]

Ok, so gave this a go on the front. Removed pads, undid bleed nipple, pushed pistons in. A small amount of fluid came out. Tightened bleed nipple, refitted pads and gave them a try. Still have the same problem. Pads are still too close to the rotor after pulling the levers.

Have I been a chicken and not let enough fluid out?

The lever feel is great, so it feels like the bleed is good, just the pistons aren't retracting enough.

 

[Twozaskars]

Is the caliper mounted in exactly the right position so that the pads are perfectly parallel to the disc?

 

[ishaw]

I'll start with the front as if I can get one sorted, I'll take what I've learned to the rear.

I've bled many a hole tech brake, even serviced a few levers and calipers too, so fairly familiar with what I've done in the past, but it's failing me here.

Revisited the front this evening, this time I pushed in the pistons, undid the bleed nipple, pushed and held lever and did the bleed nipple back up. After refitting pads and wheel, pumped the lever a few times and I was in exactly the same position as before touching anything.

On closer inspection, I think what is happening is that one piston isn't moving very freely so the other one is pushing out, closing the gap between the rotor. They are retracting enough for the rotor to spin, but it catches as there's very little space between the pad and rotor, and not a huge amount of lever pull needed before brakes engage.

I'm thinking I may need to take the pistons out and giving them and the callipers a clean.

I may have some new pistons and seals kicking around. Been a while since I've done this, so anyone who wants to refresh my memory on how to do this I'm all ears.

I think getting one out is easy as I could do this with the fluid in, although it will all flow out once piston is free unless I'm smart.

Would it then be a job of just cleaning it, hunters lube and pushing back in, then repeating on the other one?

If I'm going this far I may as well go the whole hog and give it all a good clean. To replace the seals, is that just pick out and refit new? If I've got new deals and pistons, I may as well replace if needed, but I've a few sets of these brakes so would prefer to only do it if needed, so how do I tell?

 

[Twozaskars]

Have you adjusted the reach etc at the lever?

I think getting one out is easy as I could do this with the fluid in, although it will all flow out once piston is free unless I'm smart.

If you take the pads out and just pump the brake at the disc, the easiest to move piston will come out first, hit the disc then the other will follow. That way you have some piston sticking out to grab when you remove the caliper.

A small possibility but something else is corrosion. Back when my bikes had engines in them, the Tokico 4-pots would corrode in the seal recess, forcing the seals against the pistons. It is the seals job to help retract the piston but when they're so tight against it then it won't work as intended. Brass wire brush on a dremel (ultimately followed by just binning them for something better) sorted that but I'd like to think Hope make a better product.
I've had swollen seals in hope levers but never in a caliper.
Are the discs and/or pads new or used? If used, do they match in terms of wear/unevenness?
When I fit the caliper to the bike I just put the bolts in but not quite enough for the head to touch the caliper, squeeze the brake hard, then ever so slightly tighten each bolt in turn, bit by bit, so the caliper doesn't move while you tighten the first bolt etc.
Last summer I took the Hope brakes from another bike and put them on my Five. Discs and all. A few minutes in and the back just wouldn't stop squealing. In the end I took the pads out and finished my ride. Just a case of there being a slight difference in the mounting positions of the caliper on different frames, causing the high spots on the used disc to touch and rub against (only just) the high spots on the used pad.

 

[bikeworkshop]

The lever feel is great, so it feels like the bleed is good, just the pistons aren't retracting enough.

If you get to this point, sounds like a sticky piston - so just fit new ones.

Pistons become damaged and corroded over time, it's a service part and they aren't expensive.