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Shimano Nexus 8 Premium hub problem

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Shimano Nexus 8 Premium hub problem

Old 09-02-07, 08:16 AM
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Shimano Nexus 8 Premium hub problem

Hi there.

I have a Dahon MU XL urban commuter bike. I've put perhaps 250 miles on it and really like it. I especially like the Nexus 8 hub: no deraillers, totally clean shifts, shifting while pedaling, shifting while sitting at a stop light.

Anyway, today I did a few tweaks to my bike (pedals, lights, etc). One other thing I did was to change the angle that the brake levers were mounted on the handle bars. The retailer had them too parallel to the ground, so I wanted to rotate them down about 35-degrees. To do so, I also had to loosen the shift lever set (Shimano SL-8s20). All I did was loosen the clamp screw, rotate, and re-tighten. Everything apparently went fine.

But what I now notice is that when I am in the low gears 1-3, and pedal hard from a dead stop, there is a slipping/popping/jumping noise from the hub. It's as if the gears are improperly engaged in the hub, and giving them load, pops them into a different space. For reference I'm 77kg and about 1.8m. It never did this in the past.

I checked the cabling to make sure everything is properly seated (it is). Checked that the cable was kinked or pulled funny or feeding weird (doesn't seem to be). I've made sure the two yellow lines are perfectly aligned during 4th gear by using the adjustment dial on the shift lever set. Regardless, the popping/slipping continues to happen.

This is really annoying me. I loved how bulletproof this hub was, but now it seems to be unhappy and unresponsive to the known adjustments. What should I do ?

Thanks
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Old 09-02-07, 08:55 AM
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Rotate it back where it was and see if that cures it. If it does, I would guess that when you turned the levers you caused the cable to be bent into too tight of an arc. Which is causing binding inside the cable housing resulting in poor shifting. Sounds like a new bike. Your dealer where you purchased it should take care of it for you. Probably just a minor problem.
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Old 09-02-07, 08:55 AM
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I can't see how anything you did would effect the shifting.

Did you try adjusting the barrel adjusters (does your shifter have barrel adjusters?).

It's possible that it's just coincidence, and the cables have just finally stretched to the point where they are causing mis-shifts (cable stretch and housings compress). As with the internal hubs, it's a fine line between adjustments.

Most bike shops offer one or 2 free tune-ups after you have bought a new bike from them. I'd take it back for the tune-up and definitely tell them what you did, it shouldn't matter or effect their policy. Have them tune it up, and watch them, if you can, to learn how to tune the shifting on this hub.

By the way, did you notice any change in the braking? I would hope not with your minor adjustment, but heck, I didn't find anything you did that should have altered the shifting either.
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Old 09-02-07, 08:58 AM
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Originally Posted by carlton
I would guess that when you turned the levers you caused the cable to be bent into too tight of an arc. Which is causing binding inside the cable housing resulting in poor shifting.
I thought about this, but if he rotated it down it should have relaxed the arcs (made them go out a little wider and slower). At least that's my thought, but maybe I just haven't had enough coffee yet.
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Old 09-02-07, 09:29 AM
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I have the Alfine version on a Cannondale Bad Boy 8. I also have an occasional click, however, since I changed the saddle this has started to happen, and I noticed on another thread here a click can come from the saddle.

I believe they can take a while to bed in, and I noticed on the Shimano site that clicking sounds are usual, however, slipping gears would annoy the **** out of me.
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Old 09-02-07, 11:54 AM
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This is odd. I have the exact same bike, and I did the exact same thing to replace the stock brake levers with my favorite Avid BB5 levers. Except to get off the old levers and replace them with the new ones, I had to remove the Ergon grips and the grip shifter. However, after putting everything back, everything worked just fine. I wonder if you should give Dahon in California a call and ask them.
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Old 09-02-07, 01:01 PM
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The first thing I would have suggested was making sure the two yellow lines are aligned in 4th, but since you've done that I can only think of one other thing. Once, when my Nexus-8 was doing that, I found that my chain was too loose. No problems since and I have 1200 miles on mine.
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Old 09-03-07, 01:13 AM
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Interesting. How did you determine if the chain was tight enough?
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Old 09-03-07, 01:51 AM
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i've noticed that sometimes, having the yellow lines "perfectly aligned" in the window doesn't equate to the gear pin being perfectly aligned inside the hub. i would use the barrel adjuster to fine tune it a little more, try adjusting it so that the yellow lines are misaligned slightly to one side, and then the other and see if either makes a difference. otherwise, try checking the chain tension, and if all else fails, bring it to a shop.
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Old 09-03-07, 04:26 AM
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Originally Posted by karavshin
Interesting. How did you determine if the chain was tight enough?
I don't know if your Dahon has horizontal or verticle rear dropouts. If verticle, then you might have a swing arm that provides chain tension and takes up the slack, probably not an issue here. If horizontal, like mine is, I have to put tension on the chain by moving the axle forward or backward. I try to keep the chain in a straight line around the sprockets, but also to have enough give that it will deflect about a half inch if I push down on the chain. If it deflects more than a half inch, I'll loosen the bolts, slide the axle back a little and retighten.

But if this all started after only changing the shifter on the handle bar, then I don't see how chain tension would be the problem in this case. I'd double check to see if the shifter cables didn't seat right after moving or for any sharp angles in the shifter cable somewhere.

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Old 09-03-07, 05:50 PM
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Ugh... Here's the answer: I put on SPD pedal clips, which allows me to pedal with substantially more power. This pulled the axle so hard that it slipped in the dropouts, scraping them and also pulling the wheel tight against one brake pad. The noise was the chain coming off the final tooth of the cog, not from internal to the hub. (which I should have known — it was a chain-noise similar to what I’d hear from a derailler).

Can't believe how lame my brain was.
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Old 09-03-07, 11:29 PM
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Originally Posted by karavshin
Can't believe how lame my brain was.
Just part of the learning curve. If a internal hub is new to you, there's a lot of little things you have to consider that you never had to consider before.
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Old 09-04-07, 06:44 AM
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Glad to know you solved the problem and that it wasn't the hub! As a programmer, when I get an error report I always hope it's something stupid because that's the easiest thing to fix! Just don't make the chain too tight when you have it all back together. Remember the chain always looks kind of tight on a derailluer bike because of the chain tensioner. You'll need a little slack, just not so much that the chain wants to skip (which was my problem).
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