dchsueh

Hello,

I have a Nexus-8 equipped bicycle, bought new, now 1 year old, approx 380km usage. It has not been rained on heavily.

I don't remember exactly when it started, but the hub would occasionally slip and catch a small amount 1-10 sec after a successful gear change, on upshifts only I think. Again, the new gear would engage, I'd pedal a few revolutions, and ... clunk! It would be as if the crank suddenly slips forward and then catches again. It only happens maximum once after shifting into a gear; it never occurs twice.

Shifter 4th gear alignment marks are perfect.

My bike store claimed they were not able to reproduce the problem. They replaced the shifter cable but this did not solve the problem. I am able to reproduce it easily. I would take it in again but it is difficult for me to bring the bike from my home to the selling LBS.

Has anyone experienced something like this? And if so, what remedy do you recommend, if any? Should I be pushing my LBS for an oil maintenance?

Thanks for any comments/suggestions.

chucky

Considering that the cable is new and perfectly aligned, it sounds like you're shifting while pedaling. With internal gear hubs you're generally supposed to stop pedaling while you shift (which is the opposite of what you should do with a derailleur) and, although Shimano claims you can do it either way with this hub, I'd take that claim with a grain of salt. It can be quite difficult to break the habit once you're used to one technique or the other...are you sure you aren't doing this or perhaps accidentally leaning on the shifter immediately after shifting?

Aside from that I seriously doubt you require oil maintenance which is more of an upgrade than a required maintenance task. If there is any mechanical problem I'll bet you a six pack it's either the shifter or the "cassette"/rotary (that encloses the alignment marks)...both made of plastic. It's easy to take the cassette rotary off to see if it's bent or perhaps in need of a little grease...just go through all the steps for replacing the rear cog.

dchsueh

My understanding is that Shimano Nexus/Alfine IGHs can be shifted at any time, even under moderate load (and this is different from other brands which require a relaxing of applied torque). Shimano's own Nexus 8 troubleshooting manual says that these hubs "use an assist system which aids down shifting by using pedaling force" (quote), although I personally have always successfully downshifted even while stationary.

I normally try to keep a steady cadence at the pedals, even throughout shifting. I should note that the clunking has become more frequent with use -- the hub behaved fine when new.

--

https://www.shimano.com/publish/conte...ng%20Guide.pdf

mconlonx

Try adjusting the cable tension ajuster at the shifter while you are riding and can check things out. Quarter turn at a time one way, shift through the full range--if things get worse, go back the other way. Should be a sweet spot in there somewhere, maybe not exactly where the alingment bars indicate.

chucky

It's supposed to, but nothing's perfect. Try to stop pedaling while you shift and see if the problem goes away. If it does then the answer is simply that there's nothing wrong with your hub and the shift under load feature is oversold.

I personally haven't found any difference between the shifting performance of my Nexus/Alfine hub and my other internal gear hubs...although I'm so used to adding a millisecond stagger between my leg and hand muscles that I can't shift under load even when I try (for example, other day I borrowed a derailleur bike and had lots of trouble shifting smoothly without lots of clicks and clunks because I lost the muscle memory required to shift and pedal at the exact same time...derailleurs are teh sux0rs).

This is a good suggestion. I had this problem with a Sturmey Archer 8 speed...it needed to be adjusted away from the alignment indicator, but I've found the Nexus/Alfine much more forgiving in this regard such that even if it's misadjusted it continues to work pretty well.