Shifter intermittently spinning

[CAM]

This has just started on my way home this evening, luckily in the last mile, but I need to resolve it before I ride again (8am tomorrow morning, hopefully!!)
Twice, the shifter (standard flat bar manual one) was not changing the gears. It was just turning without any tension.
The first time, I just assumed that a cable had disconnected or broken, and as it was in a convenient gear, treated it as a fixed wheel.
Then I tried again, and it worked, but short after it stopped working again.
When I got home I had a quick look and noticed that the screw that connects the black cable box onto the speed hub was not quite as tight as usual, however I would not suggest that it was loose. Having tightened it the gears re-engaged again.
It had a full service at Thorn including new cables etc 3 weeks ago, so it shouldn't be anything major.
Is it likely to be this screw that needed tightening (seems unlikely to me) or could it be something else ?
Can someone suggest what I might look at ?
Thank you

[spoof]

Hello CAM,

If your shifter was freely spinning it suggests possibly the little pulley wheel that sits inside the external shifter box (black cable box) wasn't quite engaged with the hub shifting mechanism possibly due to the external shifter box not being fully mated. You shouldn't see any gap between the external shifter box and the hub shifting mechanism it rests against when mated so you might have possibly fixed the problem already by tightening that thumb screw which would in turn pull the external shifter box into its correct seating position.

Keep an eye on it over your next rides. Sometimes when replacing the rear wheel, moving the gear into 1 or 14 prior to removal makes it a lot easier to maintain the correct gear engagement when re-inserting the wheel. It always requires a gentle move of the shifter back and forth around that gear a couple of millimeter or so just to get that external shifter box mated and seated correctly.

Hope this helps.

[JohnR]

I also would suspect the problem is caused by the the Ex-box clamp screw not being completely tight - it's the one piece of the Rohloff system which I frequently check. You'll also need to check that you've still got the full range of gears - check if the shifter turns all the way between 1st and 14th. Another good sign if the registration being good (or bad) is the change in noise between 8th and 7th gears.

[Clive.]

Hi, Conscious of your 8am deadline just an observation that if this is the solution (and it would seem the most likely) then check that you have a full set of 14 gears as you may have ended up moving the shifter whilst not engaged. If you have less than the full range it will either be only some from the top down, or only some from the bottom up, and you should be able to tell which either when riding or just when the shifter stops midway through the range. If you are missing a few at the top then set the shifter to it's lowest possible, which will be first (it won't show first on the shifter though), undo the thumbscrew and remove the black box. Move the shifter to first, and re-engage the black box and tighten the thumbscrew. If missing a few at the bottom then the opposite. Hope you can fix it before bedtime!

[CAM]

Thank you all for your timely advice - it is now resolved.

The screw was looser than I had thought with a noticeable gap, and I re-established the full range of gears by putting it into gear 14 before reseating.
Have given it a quick test ride, and will be checking it regularly once more.

Does anyone carry a spare screw for this on a long tour just in case or is it a fairly standard size ?

[JohnR]

Does anyone carry a spare screw for this on a long tour just in case or is it a fairly standard size ?

I'm 99% sure that retaining screw won't completely come out. Try unscrewing it and see if you can remove it.

Sometimes the Ex-box needs a little jiggling to make sure it is seated properly on the alignment pegs. Make sure that it's fitted properly by checking that there is zero gap between the Ex-box and its seat.A hint of grease on the mating surfaces is advisable to reduce the risk of water or dirt penetration.

[JohnR]

Also, here's the backup tool for shifter / cable problems https://www.amazon.co.uk/sourcing-Metric-Shaped-Angled-Socket/dp/B07D58GYQZ. Remove the Ex-box and use the 8mm spanner to turn the nut to select a compromise gear for limping to somewhere for suitable for fixing the problem. Fully clockwise for 1st gear and fully anti-clockwise for 14th gear.