Shimano Nexus 8 speed hub wierdness
I have a quite new Shimano Nexus 8 redline hub, recently installed on my rejuvenated Trek 720 touring bike.
Three times now it has done something very annoying. As I brake to a stop, I shift to first gear. But when I start up again, the shifter is frozen in first gear. Something is stuck at the hub; I can force the shifter to 2nd but the hub does not shift.
To unstick the hub I have had to remove the cable, which I've done by grabbing the end of the cable with pliers and pulling the cable all the way off the hub. Once this is done, the hub is free to shift again; so I put the cable back on, and the bike is good to go. But my hands are now dirty, which is not exactly what I wanted. I mean, IG hubs are supposed to be relatively maintenance free, aren't they?
As I say, this has happened three times now, which is a very low (but still unacceptably high) proportion of the time. I have probably ridden it one or two hundred miles, with several hundred successful shifts.
Anyway... has anyone else noticed this phenomenon, and if so, does anyone have any suggestion about preventing it in the future?
Broom Wagon Fodder
Wow, I have over 2500 miles on a red-band 8-speed and have not experienced that at all. I pretty much did what you did, installing it on an old Fuji road bike. I haven't heard of it from the couple of people I know that ride them either.
I'm able to take the cable off and put it back on without pliers by shifting into first and loosening it further at the barrel adjuster on the shifter (like when I need to change a tire). When I put it back on I just readjust it in 4th so that the lines line up.
I'm grasping at straws here because I can't imagine what's wrong: Are you sure the cable is installed correctly? Here are some pictures: http://www.sheldonbrown.com/nexus-mech.html
Also there is a funny plastic washer with an odd profile that goes underneath the sprocket. Could that be on backwards? There's a picture of it in the installation instructions but it was not at all obvious.
Or... what if there is a strand of cable broken inside the housing that is making stuff hang up? I'd fool around with that off the hub and figure out if it's happening in the shifter or the hub.
Last edited by reverborama; 09-02-08 at 04:10 PM.
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a couple things come to mind.
as the above poster stated, make sure you check those plastic thingies with the red and yellow dots on the hub.
secondly, maybe add a little cable grease as there could be some sticking, or just replace the cable and/or housing.
finally, you are probably using the crappy twist shifter. ive gone through 2 of those before i purchased the trigger/rapidfire shifter. i would bet this is the culprit. if you do a search you'll find threads about the twist shifter as being a "consumable" item.
It might not be related to this but a couple of times when I've shifted rapidly from, say, 7 to 1, the cable pops out at the shifter end because the hub can't respond that quickly. The cable cover then catches and stays stuck. The first couple of times this happened I wondered what the hell had happened to first gear as I couldn't engage it. Now I'm a wake up and change more deliberately.
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exactly. and doing this often i think is what causes these things to burn out fast. the trigger/thumb/rapid shifter prevents this from happening as you can only shift one gear at a time.
Originally Posted by bmorey