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I just got an Electra Townie 8i bike and the gears are acting weird. I hear clicking noises when pedaling and sometimes it slips down to a lower gear. This is especially true for 4th gear.

Is this a known issue for these internal gear systems? How can I fix it? Is this something an amateur can repair?

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2 Answers

up vote 4 down vote accepted

The 8i uses what Shimano calls a cassette joint. It's wraps the cable around the back side of the hub and as the shifter pulls the cable it moves a bracket counterclockwise backwards on the hub body. Cable tension on a brand new Nexus/Alfine 8-speed hub needs to be precise.

Do this:

  • Shift the bike into 4th gear
  • Find the cable tension indicator. There is one on the top and the bottom of the hub. The top one is a small plastic window. The bottom one is a small piece of metal painted yellow. It may be easier to find if you can flip the bike over
  • Turn the barrel adjuster on the shifter until you see the outboard yellow line move
  • Keep turning the adjuster in either direction (probably out, counterclockwise) until the yellow lines are aligned
  • shift into 3rd gear, then back into 4th and adjust again
  • shift into 5 gear, then back into 4th and adjust again
  • repeat until you're satisfied with adjustment.

This should stop your gear slippage. If the shifter cable isn't properly lubricated or there's binding somewhere then you should see a problem while dialing in the adjustment. If you can't get this adjustment right to your satisfaction take the bike back and have the shop do it. They shouldn't charge you for this if the bike is new. Make sure they test ride it so they can experience the problem.

If this is an old hub and you've ridden it misadjusted for a long time it is possible to damage the hubs innards. Replacing the hub guts should only be done at a shop that deals with these hubs regularly and has the special lubricating bath that they require for proper maintenance.

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This sounds like the shifting chain might be at the wrong tension. Look at the rear hub and you'll see a shifting chain that leads into the hub on the drivetrain side of the bike. If the Nexus 8 is anything like the Nexus 3 (which I have on my Trek cruiser), there'll be an adjuster barrel you can turn by hand to tighten or loosen the chain.

One of the nicer features of the Nexus hub is an indicator window; you should see a yellow indicator in there, and two lines on the window to line it up. You may need to fine-tune this a touch by riding it down the block and back until it shifts perfectly.

(In the event yours has no such indicator, try loosening or tightening the cable; the correct tension on the cable will allow you to use all the hub gears.)

Edit: Was over at my friend's house today, he has a Jamis with an 8-speed Nexus hub. The indicator window is smaller than on my cruiser's 3-speed hub, but it's there. The window is right up against the spokes.

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Note: I'm making an educated guess here based on my Nexus 3 hub. If any of the wrenchers here know the Shimano Nexus 8 hub well, please sanity-check this? –  Neil Fein Sep 4 '11 at 0:02
    
Certainly on your standard chain/cable operated internal gear hub this adjustment would be the first suspicion. And, as with any new bike, cables tend to stretch and adjustment is usually recommended after a month or so of use. –  Daniel R Hicks Sep 4 '11 at 2:37
    
I can't swear to the indicator window - can't find a solid picture of the hub online, and the service manual doesn't say much one way or another about this. –  Neil Fein Sep 4 '11 at 4:29
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bike.shimano.com/publish/content/global_cycle/en/us/index/… - seems that the two yellow lines on the 'cassette joint unit' need to be looked at. –  ʍǝɥʇɐɯ Sep 4 '11 at 17:10
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Will riding the bike when the gears slip damage the gear system? –  WilliamKF Sep 4 '11 at 21:36
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