Chain sagging – XT 12 speed/Hope pro 4

Hello,
Looking for some help on an annoying issue I’m having. Changed to XT 12 speed a few months back- shifter, chain, cassette, mech and had changed my hope pro 4 freehub body at the same time.

When in the 3 highest gears pedalling hard if I stop pedalling I can feel the chain slap the chain stay like the freehub isn’t stopping quick enough.
I can also replicate this is I back pedal quickly
a quarter turn whilst going along or bike in stand with the wheel spinning.

I’ve taken the freehub body off 3 times now, cleaned everything and reassembled – same issue. Thought might be too much or less grease, lightly greased – same again. Less grease – same again. I have the washer in on the back of the freehub body and there is no movement. The bearings are all smooth also. It doesn’t try and turn on its own will when the wheel is spinning

For a separate issue the mech was sticking the other day so I took the clutch out, cleaned, greased and reinstalled. The mech is aligned straight and the hanger is not bent, as it happens when I stop pedalling I assume it’s freehub related?

Only other thing I thought was perhaps I have a few too many links in the chain (it looks right and I did an online size guide) and it’s not holding enough pressure on freehub body when futhest from hub body under pressure.

Any help appreciated, it’s sending me nuts now.

Is the green hub seal fully home?

Is the Chaim stack when the wheel is stationary?

The Green seal is fully in place all the way round and chain only sags when stopping pedalling hard or back pedalling in bottom 3 gears!

Check the b screw – it has a huge impact on chain tension. This helped get mine right (same set up as you).

Fewer links might help if there’s a few too many. Shortening the chain will force a B screw adjustment anyway.

If it’s full suspension, check where maximum chain growth is though.

Is the spacer in the freehub in the correct position, there is n exploded view on the hopetech website.

As per the diagram and also Hope install video!

I’ll take another look at the B screw, but this was set up with the marks on the back of the mech against the cassette teeth

Elephant in the room is mech issues:
1) Is the clutch too strong for the spring? Its adjustable.
2) My 5 year old 11 speed mech spring has just died, full dismantle and service discovered this. I tried winding it around another turn but then it just goes coil bound > new mech.

Dodgy jockey wheels can do this.
I had it the other month. 11 speed XT, new ish jockey wheels as the old ones had worn out. One of the new ones had no grease/was siff and would make the chain go slack if I back pedalled or freewheeld. A quick clean and regrease sorted it.

Jockey wheels running freely.
Tried the b screw and didn’t make any difference.
Checked clutch isn’t too tight also.
It’s only the bottom 3 gears it does it in with the smallest being the worst, ive taken a poor video to show

Are you sure chain is not too long?
Do that again but with clutch off?

If you have taken the freehub off the most likely thing is its put back wrongly IMO seal or spacers. However that video does not look like a sticky freehub or jockey wheels – it looks fairly normal to me. a new seal will have some friction in it

as well as checking the clutch, check the mech cage pivots freely

Cheers everyone. I called hope and they recommended taking the green seal out and seeing if changed, it didn’t.
They said however they managed to replicate it on a bike in workshop so might be normal, but def doesn’t feel it. And never had it before.

Mech – all cleaned and free, cage and clutch.

Think chain length is my next attempt, take out a couple of links and see

Think chain length is my next attempt, take out a couple of links and see

I think start with looking at shimano instructions and making sure the length is correct.

How thin is your grease?

My old Pro2 did this once when I used thicker Shimano bearing grease.

I think mine might be doing something like that when I stop pedaling and immediately backpedal 1/8th-ish to get the pedals level. Not sure which gears, I wouldn’t hear the chainstay being slapped but I do feel a slight resistance momentarily through the pedals. I had put it down to just being how it is with 12spd and a 44 point of engagement hub (one or the other, or the combination). Deore 12sd & Pro 4, factory built bike. I’d forgotten about it until I read this; maybe it’s stopped happening now, I’ve got used to it, or I’ve changed my pedal-levelling technique.

Just been to the garage. Mine does what yours does in 12th, down 1-2cm at which point it touches the chainstay. No such movement in 1st, didn’t try any other gears. I also realised it doesn’t matter whether the wheel is spinning or not – same result in both gears. It makes sense that only higher gears are affected as the gear ratio between the cranks and hub applies to backpedaling too.

Chain looks as if it might be too long. The mech looks far too horizontal but it might be the camera angle. Use the Shimano dealer guide from si.shimano.com to get the correct length.

I don’t have 12 speed yet (my bike is being built as we speak) but popped onto this thread – loving the community feedback and help you are getting – everyone loves a problem to solve! Keep going guys, am watching with nerdy interest..

Another video and small update, mech all cleaned as said before, jockey wheels running free. Checked chain length and it was 1 link above recommended but I had to take 2 out to make it fit with the links, so I’ve done that and still no better.
I’m down to thinking it’s got to be something with the rear mech now? I will try and borrow a friends wheel and see if anything different happens.

What’s your chainring? Is it one specifically sold for Shimano 12 speed? If not it might be the chain being retained too long on the teeth of the chain ring as you pedal backwards.

@5plusn8

My 5 year old 11 speed mech spring has just died, full dismantle and service discovered this. I tried winding it around another turn but then it just goes coil bound > new mech.

You can replace that part of the rest of the mech is good. Plenty of dead mechs around to salvage parts from.

You can replace that part of the rest of the mech is good. Plenty of dead mechs around to salvage parts from.

Where???

@OP I am struggling to see what is wrong now, all drivetrains do this?

@OP I am struggling to see what is wrong now, all drivetrains do this?

Yeah – that fast stabby back spin expecting the chain to “push” the cassette? – it’s it a bit like, er, trying to play snooker with a rope?

Yeah I totally get that, but this is happens when I stop pedalling at trail speed and the stand is only way I can simulate it for the camera!
I’m going to try different wheel and see any difference

Well you’re in good company.
https://www.cyclingweekly.com/products/why-does-cavs-chain-keep-coming-off-in-sprints

What chain have you got on there – and what chainring is it?

I wonder if the poster above is into something and the chainring is holding onto the chain too long for a split second. I don’t rate Shimano chains at all for 12 speed – prefer both Sram and KMC.

The Shimano chains don’t play nicely with all non Shimano chainrings.

Reasonably sure the dt Swiss 240 on my cross bike does this, albeit only when the rear wheel is going round at road speeds, so I only tend to see it in the small sprockets. On that I’m halfway sure it’s down to a slight reluctance of the two halves of the ratchet to let go of each other.

As above, the only obvious thing I could think of for a hope hub would be the freehub seal dragging the freehub round with the hub.

Tried with the different wheel still same issue, god knows at this stage without trying a different mech. It’s almost like the mech spring isn’t strong enough to hold the tension when pressures off

But what about your chainring?

I actually really rate Shimano chains, the shifting is so much better than SRAM Eagle when used with a Shimano cassette that it’s mind blowing.

Chainring in good condition, 9 months old. That wouldn’t affect it when pedalling and it slapping down when stopping pedalling. I get that it could affect when back pedalling but I can’t film it when moving!

I’ve got this same issue on my new bike & new Deore groupset. My chainstay got a nasty scratch from the chain coming down just aft of the chainring. I’ve got the b-screw/mech height set correctly & the chain length set as per the instructions for a hardtail.

I think there’s too much friction in the Bitex freehub + not enough tension on the chain, although it seems pretty tight. I’ve already upped the clutch tension but it didn’t help. I’ve not yet taken out grease from the hub but will likely try that next. I may be able to take another link out of the chain but I’m leaving that as the last resort as I don’t want to make it too short.

Does anyone know if it is possible to increase the mech spring tension? I’ve previously increased the spring tension on a Tiagra mech, but there isn’t a second hole to put the spring end into on the back of the pulley guide plate.

Edit: possibly could be chain needing the original Shimano grease flushed out as I’ve not yet done that, as per this thread: https://singletrackworld.com/forum/topic/freehub-drag-ideas/