Author Topic: Gear shifter doesn't want to turn  (Read 3203 times)

Oswestry Ken

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Gear shifter doesn't want to turn
« on: January 25, 2021, 07:51:12 pm »
After just 1200 miles my gear shifter (on comfort bars) was becoming more and more difficult to twist. On Saturday it was so bad I thought I needed to find the cause and sort it out.
I disconnected the external gear mech using the hand tightened screw and had a go with the twist grip - it was still very stiff to turn and so I ruled out a problem with the actual speedhub.
I removed the plate of the gear mech by taking out the two torx screws and had a look inside. It was full of very fine grit and this seemed to be the cause of the problem.
I unwound the cable from the little circular disc, tipped out the grit, cleaned everything up and eventually managed to coil the wire up and put it all back together. It's still not exactly smooth (as on my wife's cheap Dawes bike which has twist grip derailleur gears) but is much better than Saturday.
My question is, is this a common problem with these exterior gear mechs?
Any help/advice gratefully received.

Danneaux

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Re: Gear shifter doesn't want to turn
« Reply #1 on: January 25, 2021, 08:30:33 pm »
Quote
...It was full of very fine grit and this seemed to be the cause of the problem.
I unwound the cable from the little circular disc, tipped out the grit...My question is, is this a common problem with these exterior gear mechs?
I've not found this to be common in my experience and there is a low incidence of reports for contamination of the external (shifting) gearbox, provided...
Quote
Any help/advice gratefully received.
...
a) The cover is firmly on (but not too tight and remember to apply anti-seize to the screws)
...and...
b) There is a barrier to entry. Rohloff recommend periodic lubrication of the EX shift-box. I prefer to pack my external shift-box with Phil Wood waterproof grease. It has formed an effective seal for e against both water and dust (a potential problem otherwise considering I enjoy touring in the desert where talc-fine alkali dust blows on the wind and is kicked up by the tires). I packed mine shortly after I got my Nomad in 2012 and it has not required further service (I check about every 6-8 months to be sure).
See: http://thorncyclesforum.co.uk/index.php?topic=4523.msg36175#msg36175
Followup here:
http://thorncyclesforum.co.uk/index.php?topic=4523.msg95429#msg95429

See also:
http://thorncyclesforum.co.uk/index.php?topic=13718.msg102011#msg102011
http://thorncyclesforum.co.uk/index.php?topic=12877

Any chance the thumbscrew wasn't fully tightened so the gearbox failed to fully seat, leaving an avenue for grit to enter?


Best,

Dan.
« Last Edit: January 25, 2021, 09:38:43 pm by Danneaux »

UKTony

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Re: Gear shifter doesn't want to turn
« Reply #2 on: January 25, 2021, 09:09:17 pm »
All I can think of is if the cable adjusters on the ex box are not adjusted corr3ctly (not enough play) this can make turning the shifter difficult.

Oswestry Ken

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Re: Gear shifter doesn't want to turn
« Reply #3 on: January 25, 2021, 10:26:51 pm »
Quote
...It was full of very fine grit and this seemed to be the cause of the problem.
I unwound the cable from the little circular disc, tipped out the grit...My question is, is this a common problem with these exterior gear mechs?
I've not found this to be common in my experience and there is a low incidence of reports for contamination of the external (shifting) gearbox, provided...
Quote
Any help/advice gratefully received.
...
a) The cover is firmly on (but not too tight and remember to apply anti-seize to the screws)
...and...
b) There is a barrier to entry. Rohloff recommend periodic lubrication of the EX shift-box. I prefer to pack my external shift-box with Phil Wood waterproof grease. It has formed an effective seal for e against both water and dust (a potential problem otherwise considering I enjoy touring in the desert where talc-fine alkali dust blows on the wind and is kicked up by the tires). I packed mine shortly after I got my Nomad in 2012 and it has not required further service (I check about every 6-8 months to be sure).
See: http://thorncyclesforum.co.uk/index.php?topic=4523.msg36175#msg36175
Followup here:
http://thorncyclesforum.co.uk/index.php?topic=4523.msg95429#msg95429

See also:
http://thorncyclesforum.co.uk/index.php?topic=13718.msg102011#msg102011
http://thorncyclesforum.co.uk/index.php?topic=12877

Any chance the thumbscrew wasn't fully tightened so the gearbox failed to fully seat, leaving an avenue for grit to enter?


Best,

Dan.


What I have noticed is that when I tighten the thumbscrew a reasonable amount it allows a gap to form at the bottom, where it fits against the hub.
The main problem only became apparent when I removed the plate which is held on by the two torx screws. Maybe it will be okay from now on. I'll soon find out.

PH

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Re: Gear shifter doesn't want to turn
« Reply #4 on: January 26, 2021, 12:44:26 am »
Shifting does deteriorate with usage, though it's usually the cables, I change mine every couple of years, your mileage doesn't sound enough to have caused much wear, but other factors might be relevant. Here is how I would look at it and the order of elimination.
First there's four elements, shifter>cable>gear mech>hub
You've eliminated the hub, which is a relief as that would be the complex one.
 I'd take the pully out of the ex-box and pull the inner cables.  You can do this without releasing them from the pulley.  You should be able to spin the shifter by pulling the cables with very little effort.  Then check there's no fraying where they wrap around the pulley.
If the shifter spins easily and there's no fraying, you've eliminated the cables and the shifter.  Just the mechanism left, and that's been covered above so I won't repeat it.
if it's not spinning easily, you need to determine if it's the cables or the shifter. 
Cables off the pulley and pulled through the outers enough to expose a few cm by the shifter.  Does the shifter spin easily pulling the cables by the shifter?  If yes, then it has to be the cables, you could try lubricating and cleaning, maybe pull them out and see if there's muck or corrosion.  It's not a big or expensive job to replace them.
If the shifter doesn't spin  easily, remove the cables and see if it does than. Shine a light down the holes and try and see the groves the cables sit in and where the cable head sits, if it isn't seated right it will make the shifter stiff.  With no cables in it, the shifter should turn with the lightest of touch.  if it does, then it has to be either the cables or the way they was fitted, fit a new cable and hope that cures it.  If the shifter was stiff without the cable or the new cable hasn't sorted it, you'll have to dismantle the shifter, when you do so pay attention to the O rings, it might just need a clean, or you might see there's some wear, exploded diagram here
https://www.rohloff.de/en/service/handbook/speedhub/assembly/twist-shifter

It isn't as big a job as the above might seem, it's probably taken me longer to type it than it would to do it! If you're taking inners in and out, be careful not to fray the ends.  If you do, or need fresh cuts to fit back into the pulley, cutting corresponding amounts off the inners and outers brings it back to the same at the cost of a slightly tighter curve at the bars.
« Last Edit: January 26, 2021, 12:54:30 am by PH »

Oswestry Ken

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Re: Gear shifter doesn't want to turn
« Reply #5 on: January 26, 2021, 11:40:57 am »
Thanks for that very detailed help, PH.
I have just checked the shifting again, now, and I think it is back to how it used to be when I first had the bike.
My only question now is whether the gap that can be seen in the photo is usual.

Aleman

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Re: Gear shifter doesn't want to turn
« Reply #6 on: January 26, 2021, 11:50:25 am »
To me that looks as though the pulley hasn't seated fully and engaged with the gear in the socket

PH

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Re: Gear shifter doesn't want to turn
« Reply #7 on: January 26, 2021, 01:38:10 pm »
My only question now is whether the gap that can be seen in the photo is usual.
No that doesn't look right. 
Try backing the thumbscrew off half a turn, jiggling the shifter back and forth while retightening.  BUT - don't force anything, if it doesn't fit or tighten with little effort, something is wrong.

Andre Jute

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Re: Gear shifter doesn't want to turn
« Reply #8 on: January 26, 2021, 04:12:58 pm »
That's a machined pair of mating faces. You should see no gap. inside you've no doubt already inspected the socketlike shape on the thumbscrew side, and the brass nutlike thingy on the hubside that meet to change the gears. Open it up again and this time notice how little surface these two crucial parts have to mate in: that's the reason the two large mating surfaces of the containers, so to speak, should be flush to each other. If they're not, crucial parts of your gearbox will wear faster than normal, and the change will be increasingly rough.

As Paul says, wriggle the rotary control a little until you can match the surfaces easily, no force required.

And, another tip, before you undo the thumbscrew, leave the box in gear 14 or gear 1 to get it together again easily. After you fit the klickbox back, you need to check that you have 14 gears; if you get it wrong, you'll have fewer gears and need to do it over.

Oswestry Ken

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Re: Gear shifter doesn't want to turn
« Reply #9 on: January 26, 2021, 07:15:56 pm »
Well, now I'm a little more worried than I was. I have opened it all up again this afternoon and cleaned everything again. I just can't get the two surfaces to be flush. No amount of jiggling allow them to go dead flush when I tighten the thumbscrew.
When I cleaned off all the waterproof grease I had put in the gap did lessen. As soon as I put the grease back in, the gap became as in the photo.
I don't suppose anyone has a photo of their setup do you?
Although, even if you did, I'm sure I won't be able to get these surfaces to match up without any gap.
I did try it without the gear mechanism in the clickbox and then they fitted flush. With it in there's no way.
On the plus side, all the gears work fine from 1 to 14.
Any more ideas, anyone.

Oswestry Ken

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Re: Gear shifter doesn't want to turn
« Reply #10 on: January 26, 2021, 07:36:49 pm »
And now I'm not as worried.
I took some of the grease out and tried again.
It seems reasonable now - what do you think, please?

PH

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Re: Gear shifter doesn't want to turn
« Reply #11 on: January 26, 2021, 08:14:00 pm »
That looks fine to me

Oswestry Ken

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Re: Gear shifter doesn't want to turn
« Reply #12 on: January 26, 2021, 10:58:13 pm »
Thanks, PH, that reassures me.

Andre Jute

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Re: Gear shifter doesn't want to turn
« Reply #13 on: January 27, 2021, 11:22:04 am »
Agree with Paul, it looks good.

One final tip: If you've totally bolloxed your gear change mechanism all the way from the rotary control on the handlebar to the klickbox on the hub -- or even if a cable has just broken in the middle of nowhere, an 8mm open spanner or a socket can be used to change the gear manually by turning the brass nut that becomes visible when the click box is removed. I carry both in my tiny toolkit because my Rohloff-equipped bike has such a long wheelbase, I find it more convenient to change the gear by spanner when I forget to leave it in 1 or 14 which is almost always as I remove the klickbox only once a year when the bike gets its big service of oil change and shot of grease and a quick once-over everywhere with the torque wrenches.