I just bought a new bike and it has the nexus 7 internal hub. This is my first internal hub. I love to ride but admittedly don't know much about the mechanics of bikes. I'm 57 and mostly ride the bike path in Prov. Ri which has 4 very steep hills and then many miles of flat path of which I thought this would be a good choice given the flats and low maintenance. Admittedly it is slow going up the hills but thats ok with me. I seem to be having a problem with the second gear, downshifting. It takes sometimes many rotations of the pedals to get it to change into 2nd. The bike shop adjusted the cables and made me aware of the yellow markers and how to adjust with the cable. Seemed to be better but it still doesn't shift gears right away.The yellow marks are spot on. I adjusted my riding style to give a 1/4 pedal backwards and it works well that way to get into 2nd gear. I'm stuck between is this normal or is it possibly a problem with the hub? it's brand new, put 60 miles on it. The cables are obviously new and I've read it usually a cable adjustment. Do I simply need to adjust my riding style and not expect it to engage instantly like the other gears do? With my derailer I changed gears constantly but am thinking I should adjust to methodically clicking one gear to the next and to just ride in 4th gear unless necessary to change. I dont shift under load. Sorry if this sounds a bit messy. Is it me or the bike or both?
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4"to just ride in 4th gear unless necessary to change" - that's not necessary, I use the Alfine 8 IGH and I shift all the time, particularly because it's so easy with an IGH. You shouldn't shift under load, which could damage the internals. With a bit of practice, you'll learn how to simultaneously shift and pedal slightly slower for a split second, such that the freehub/clutch mechanisms disengages momentarily and the shift happens quickly. This enables quick shifting and long life of the IGH.– ErlkoenigJan 26, 2021 at 8:55
4 Answers
It sounds a little like you are shifting while pedaling. That's the opposite of how internal hubs work and will tend to cause the shift to happen delayed or never, and if done habitually for long enough is bad for the hub.
If you've got the yellow mark dialed and you're shifting only while coasting, and it's happening as you get into the slacker cable tension gears, it is possible there's a kink in the cable somewhere hidden by the housing, and it's causing friction that is making the shifting erratic.
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3My approach with SRAM 7-speed IGH has always been to turn the shift-grip while pedaling (which did not change the gears due to the continuous load on the drive train), and then to release the force on the pedals for a split second to actually perform the switch. I don't know the Nexus 7, but for my SRAM, this usually worked like a charm. No extended coasting or back-rotation of the pedals was necessary. Jan 26, 2021 at 8:03
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@cmaster-reinstatemonica I'm pretty sure that's exactly right for most modern hubs. It's also what I do on my Alfine 11. If it doesn't work, that's just because those hubs are often pretty finnicky.– NobodyJan 26, 2021 at 11:00
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Slacker cable means higher gear on Shimano IGH, so it's probably not a cable kink as it happens in the 2nd gear. Jan 26, 2021 at 14:50
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1From I was told, it is ok to shift while pedaling but not under load. You are saying don't pedal. I'll try that.– DavidJan 28, 2021 at 16:52
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@David What you were told is exactly right. Not pedalling applies mostly to historical hubs, it's not the recommended way on any of the models I know.– NobodyJan 28, 2021 at 17:36
I've had an Alfine hub, where the red/yellow lines weren't exactly right. I had to tighten the wire so it was just out of position, then shifting was much better.
Don't assume the mark is perfect, you may need to twiddle it to get the best-sounding changes.
I suggest you keep complaining to your dealer. Those Shimano gear hubs can be finnicky and quality control is not great - sometimes there is just a subtle manufacturing defect which causes bad shifting. For reference, I had a much more expensive Shimano hub replaced on warranty twice before I got one that worked properly.
But once correctly set up and if the hub is not defective, they should shift quite ok. The way to shift is to reduce pressure on the pedals, but keep pedaling, shift, wait until you feel the shift has happened, and then increase pressure on the pedals again. Pedaling backwards should not be necessary and could be bad for the hub.
The actual shifting is delayed a bit, the controls just tell the hub which gear it should shift to, and the actual shifting is delayed until the hub can shift. Usually (pedalling with little force) this should happen in a split second, otherwise you can sometimes hear the mechanism trying to shift but not succeeding.
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It's a Public Bike and honestly they don't seem responsive at all but if it continues I will be more forceful.– DavidJan 28, 2021 at 16:54
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@David Is 'Public' the brand? But that shouldn't be important, as long as you have warranty you should be able to complain to the seller. It doesn't matter to you as the buyer if the seller goes on to complain to some bike assembly company, or complain to the manufacturer of the hub (Shimano) or whoever.– NobodyJan 28, 2021 at 17:33
I had a similar problem with a Nexus 8 hub where it would shift ok to upper gears, but sometimes it had problems downshifting to lighter gears. I discovered that my gear cable has a small fray that added some friction when downshifting.
As the bike is new, I would thoroughly check if the gear cable does not make tight turns, is well seated in the cable stops or has anything weird with it. If you don't find anything, I would replace the entire cable and casing because sometimes there is some bad cuts in the cable casing that adds friction that makes downshifting less precise or a terminal is rubbing with the cable. I would be a rather complex job to do at home and you would have to have some special tools, so I would recommend taking to the shop.
