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.

 

[ishaw]

Yes, I may go down that route. Frustrating as the bikes built, just brakes not playing ball.

I have always sorted of not understood how hydraulics work. I mean I think I do, but this has me questioning.

So, as there is a vacuum, and squeeze of fluid down will be followed by a sucking back up right?

In my current situation, the bleed was done with the pistons fully retracted, so after squeezing the lever a few times, the pistons are staying out farther than when bled, but lever feel is still solid/good. I'd expect some sort of give or softness until the fluid hits the pistons. I know I'm wrong, as it's not happening that way. Hence doubting what I thought I knew.

 

[Cloverleaf]

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?

It does sound like things are a bit sticky. Which caliper and lever are they? 4 pots are a little fussier about dirty pistons than two, but not onerously so in my view. Lever wise the older ones are a lot simpler when bleeding in that you don't need to do anything with the adjusters, whereas the later Tech ones you're best off adjusting the reach and throw so that they're at max as this will allow you to push more fluid through the system with each pump.

If you have a piston that's not returning properly it'll no doubt be slightly lazy in contacting the rotor too. Get yourself some Hunter silicone lube and use this to lube the pistons. I do it periodically on mine, particularly those with phenolic pistons which lose their shine with use and can attract dirt into these micro scratches. Remove the pads, give the levers a few pumps (you may need to hold the other pistons in with a tyre lever etc to get the sticky one out far enough, and apply some of the lube to the piston and the gap between the piston and caliper body. Push the pistons back in and repeat. You may need to cycle them a few times but if you wipe off any dirt that appears (like you would with a fork stanchion) then this should restore performance. Of course if it's really far gone then a new seal kit and/or piston will eventually be needed but honestly, I've saved so many brakes this way when guys I ride with are whinging about their brakes not working after a run (not calling you a whinger, any whinging here is perfectly justified!).

The latest brakes have switched to a hard anodised piston bucket with phenolic insert which seems to be the happy medium between heat transfer into the caliper from the pads, and piston longevity. Then again the seals and pistons in my original V4's lasted nearly nine years before I rebuilt them, and you still need to lube the pistons up occasionally even then. To be fair you need to do this on most brakes, but people don't. Hope use lighter return springs than a lot of manufacturers which means that when a piston is sticky it seems to be more noticeable. For me I'd happily have this slight extra work of keeping the pistons lubed in return for a lighter lever. SRAM are the opposite where a sticky piston still detracts from performance but is less noticeable at first due to the stronger return springs, so when it feels bad, it's really bad and often leads to the junking of a brake that with some TLC would have lasted years (until one of the other SRAM issues reared its head of course).

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.

Yep, I've had to rebuild the APs on my Impreza a few times for this reason as they have two square cross sections seals per piston and no boot, rather than one seal and a dust boot. Salt water gets behind the seal and gradually corrodes the caliper body which pushes the seal out into the piston and jams it. I had about 150psi in one of them before it finally released the piston. The rears were similar albeit at least I could punch the inner pistons out with a drift and a 2lb lump hammer. It still took some serious swinging. At least most MTBs don't see the same amount of salt as a road car or motorbike.

Yes, I may go down that route. Frustrating as the bikes built, just brakes not playing ball.

I have always sorted of not understood how hydraulics work. I mean I think I do, but this has me questioning.

So, as there is a vacuum, and squeeze of fluid down will be followed by a sucking back up right?

In my current situation, the bleed was done with the pistons fully retracted, so after squeezing the lever a few times, the pistons are staying out farther than when bled, but lever feel is still solid/good. I'd expect some sort of give or softness until the fluid hits the pistons. I know I'm wrong, as it's not happening that way. Hence doubting what I thought I knew.

I think you're imagining it as a closed system like the early Hopes. With Open brakes the fluid comes from the reservoir to fill the space, which is kinda what the adjuster on top of the MC used to do, so if you removed the top cap now you'd see the diaphragm sucked down as the fluid has filled the extra space behind the pistons in the caliper. When you bleed a caliper with the pistons out and push them back in once the diaphragm is back on you have the opposite issue as there's nowhere to go and your brake lever doesn't move as much as it should.

I'd try the lubing of the piston but if that doesn't work then a rebuild is pretty straightforward. There are a few differences between the brakes in the cap tools you need (assuming of course yours are mono bloc calipers rather than the original bolted stuff). For mono blocs it's the simplest as you just hold something against the outer pistons (the ones with the caps) and squeeze the lever until the pistons are at the point of coming out. Careful here as fluid will escape. If one is coming out easily and another isn't then block the freely moving one until the stuck one is nearly out, and then let both comet together. Once you can wobble them they're nearly there. Then you can remove the bore caps from the other side of the caliper and simply push the pistons out from behind with your fingers. I use a plastic dental like pick for removing the seals as it minimises risk of scratching the seal faces.