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Old 05-14-12, 01:54 AM   #1
zaskargo
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Nexus 3-speed very slow to downshift

I have a Nexus 3-speed hub (on an Electra Amsterdam women's) that is slow to downshift. I've adjusted the tension correctly, I believe, so that the yellow indicator is centered between the lines in second gear. Upshifts are immediate and clean.

The problem is that when downshifting from third to second, or second to first, the shift is quite delayed -- it often takes several seconds and several rotations of the cranks before the shift actually happens. I've tried adjusting the cable so that it is "closer" to the lower gears, but it doesn't matter. It seems like it's not a problem of the cable pulling correctly, but rather an internal stickiness that causes the shift to take some time to take effect.

Any suggestions? Thanks!
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Old 05-14-12, 08:30 AM   #2
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Shifting in the direction where you're pulling the cable is usually sharper than that there the hub's return spring is. However if the difference is big, it might be that you're not easing off some pedal pressure during the shift. The sliding parts that make the transition from one drive path to the other are under load when you're pedaling and the added friction of the load can be too much for the return spring to overcome.
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Old 05-14-12, 10:02 PM   #3
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Originally Posted by FBinNY View Post
Shifting in the direction where you're pulling the cable is usually sharper than that there the hub's return spring is. However if the difference is big, it might be that you're not easing off some pedal pressure during the shift. The sliding parts that make the transition from one drive path to the other are under load when you're pedaling and the added friction of the load can be too much for the return spring to overcome.
Thanks for the response. It's definitely not just a matter of easing up on the pedals, that doesn't seem to make much difference. I have other 7- and 3-speed Nexus bikes so I'm used to the feel of downshifting and this can be 2 - 5 seconds longer than on those bikes (where it's nearly instantaneous). Maybe it's an issue with the return spring? Maybe I need to lube it inside somehow? Though I hear that is very rarely needed.
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Old 05-14-12, 10:21 PM   #4
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Something is making the clutch too sticky for the sprint. Take a minute to work it back and forth off the bike and see if it returns quickly or you can detect the same sluggishness. You don't have to take the wheel off or even disconnect the cable. Simply find a bare area and pull it away from the frame like a bow string and let it snap back.

If the hub quickly pulls up the slack, then odds are the hub isn't the issue. Check the cable run for a hard bend or crushed housing. Otherwise it might simply be a worn cable housing, or one with dried or sticky lube. Sticky cables are the #1 cause of similar problems on derailleurs, so there's no reason to assume that an IGH would be immune.
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Old 05-15-12, 04:33 AM   #5
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I suggest pulling the bell crank off the side of the axle, and trying pushing the shift rod in a few times. If the rod comes back out freely, then your problem is probably in the shifter or cable. If the rod comes out with resistance, the problem is in the rod or in the hub. Check the rod by pulling it out and see if it is coated in a light grey grease. If the rod is not covered in grease, and meets resistance in popping out, you may wish to lube the hub through the shift rod hole.
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Old 05-15-12, 05:46 AM   #6
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I think you'll be headed down the right road with the advice so far. Just in case, here's the rebuild/overhaul instructions for the Nexus 3, with a trouble-shooting chart on page 11.
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Old 05-15-12, 03:00 PM   #7
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I'm inclined to think your problem is most likely the shift rod is either bent or gummed up. It's a low normal hub, so upshifts are positive action, downshifts are spring return.
I'm with the guy that said to pull off the bell crank and pull out the shift rod. Roll it on a flat surface to check that it's straight, and clean and oil it before re installing.
I've solved many similar issues this way.
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