Shimano Nexus 8 Issue

edmunds

My Shimano Nexus 8 based bike has run great for ~3 years with only cable adjustments needed, but now it seems the part joining the sprocket and the hub has popped out (or unscrewed) and I presume it needs a specialist tool to tighten it again.

The bike still cycles and changes gear but will frequently lock up while freewheeling and spin freely when pedaling. There is no noise from the hub so I don't think its damaged internally.

Anyone else seen this problem?

Also can anyone recommend a shop that's good for hub gear related repairs? My local shop won't touch it!

THanks/

Doctor Bob

I haven't experienced that particular problem with my Nexus 8, but I've had a few other ones over the 4 years I've had the hub.

My initial guesss is that the thin black lockring which keeps the cassette in place might have come loose. If so, it's an easy thing to fix if the part isn't broken- just align it correctly, push it in and turn it. If broken, it's easy enough for your LBS to replace.

Sheldon Brown has the Nexus 8 manual here.

Shimano has a couple of other useful documents here and here.

(All three of these are relatively easy to understand if you have a bare minimum of technical knowledge.)

If you're in Dublin, I'd recommend Cycleways for repairs. There's a chap called Konrad who knows his way around hub gears. Alternatively, I've heard that one of the mechanics in Joe Daly's is also pretty handy, but I don't have first hand experience of getting hub gears repaired there.

edmunds

@Doctor_Bob, thanks! I have seen those manuals and they are a bit beyond my mechanical ability (and patience!)

I have used Cycleways for repairs in the past and though they get the job done they seem a little pricey and rushed (last time they gave me back my bike assembled wrongly so the back wheel lock up as I tried to pedal off!).

Any other recommendations for Dublin City Centre bike shops that are handy with hubs would be much appreciated.

Doctor Bob

The manuals are a bit intimidating alright, but no more difficult than Lego instructions. The first time I took the hub apart I was very cautious, but following the steps was fine and it went back together very easily- though I should mention that I didn't go anywhere near the innards of the hub! I just took off the cassette, the lockring, the sprocket and all the parts outside the hub itself, and putting them back on was just that process in reverse.

If it's been a while since you were in Cycleways, you might not know about their booking system. These days, you book in advance and get same day return. They're still kind of pricey, but that might be to deter punters coming in for simple repairs- or maybe it's just to pay the mechanics a decent wage!

Re other shops- I'd go for shops with a commuter focus rather than a road or mtb focus. Maybe EuroCycles opposite Grogan's, maybe City Cycles on Blackhall Place. (I haven't used either one myself.)

One other thing I'd mention- if you've only ever tweaked the cable, it might be time to re-lube the gears (internally). It should be done about once a year or so, though your mileage may vary.

edmunds

I think I'll give it another go this weekend.. being honest though last time I got stuck when it came to disconnecting the shifter cable (no problem with removing the chain or the brake cable).. This seems to be held in place with a hexagonal nut which I couldn't see how to undo.. or do you have to disassemble some more before removing the shifter cable?

Doctor Bob

Make the shifter cable as slack as possible by putting it in 1st gear, then with a little bit of force the cable should just pop out of the 'socket' that the nut sits in (the socket is horseshoe-shaped rather than a hole). I've never loosened that nut, because I fear that I wouldn't get it back on in the same place and it's important for cable tension and gear indexing.

Hope this helps!

edmunds

ahhh didn't try that, sounds straightforward enough.

Thanks for the help, i'll let you know how I get on!

denisor

I know its been a while, but I have a Nexus 8 on my Trek Soho, and as a heads up to anyone its worthwhile also lubing the cable that comes out of the black cable holder as the hub, as this can make the gear change very very smooth.

Civilian_Target

Ooh, I had this problem with my old SRAM 7 after a few years - I don't know what the English word was but I went to the bike shop in France, they told me it was déboitiaé (unboxed), and said it could be easily fixed... which is was. What caused the problem was that the stabilization attachement, that keeps the hub stationary while the wheel rotates, became detached from the frame.

However, it was the start of a set of troublesome issues with the hub, I think caused by the fact that I 'unboxed' it coming down a steep hill, which screwed some internal component of the hub. I eventually just did a single-speed conversion the year after.

I hope things work out better for you. While hubs are generally nice to use, and very reliable, when they do break they can be a real pain!