Problem with Shimano Nexus 8

[Tvrtko Ursulin]

Hi to all,

This is my first post here and I hope it is OK to skip introduction and go
straight to the problem.

I own a Carrera Subway 8 bicycle with Shimano Nexus 8 hub gears since 2004.
Something like two years ago it started to malfunction so I took it to a
local shop where they failed to repair it, but they are not really familiar
with Nexus so that's not unexpected. After that I've put the whole thing on
my list to investigate and fix, but kept postponing it until now.

What the problem actually is.. I cannot shift to gear four and lower, and
after trying I can't shift back to fifth, I just lose power then. There is
that yellow line for adjusting the shifter which then needs to be
re-adjusted before I can change to fifth again. It seems that the attempt
to change to fourth breaks the alignment. And by re-adjusting I mean that
the whole assembly where the yellow line is can be rotated by hand. It only
goes from position 'bad' to position 'aligned', it can't be rotated freely
around. So to clarify, it can then be moved by hand back into the aligned
position when gears five and higher again work fine.

For those with schematics that assembly is CJ-8S20 and Inter-8 Hub I have is
SG-8R25. I have dismantled that assembly but couldn't visually notice
anything wrong with it. Mind you I am not very experienced with bicycle
repair so that may not mean a lot.

I hope someone with some insight reads this group and that I have managed to
describe the problem clearly.

Thanks in advance,

Tvrtko

 

[Ryan Cousineau]

In article <[email protected]>,
Tvrtko Ursulin <[email protected]> wrote:

> I own a Carrera Subway 8 bicycle with Shimano Nexus 8 hub gears since 2004.
> Something like two years ago it started to malfunction so I took it to a
> local shop where they failed to repair it, but they are not really familiar
> with Nexus so that's not unexpected. After that I've put the whole thing on
> my list to investigate and fix, but kept postponing it until now.
>
> What the problem actually is.. I cannot shift to gear four and lower, and
> after trying I can't shift back to fifth, I just lose power then. There is
> that yellow line for adjusting the shifter which then needs to be
> re-adjusted before I can change to fifth again. It seems that the attempt
> to change to fourth breaks the alignment. And by re-adjusting I mean that
> the whole assembly where the yellow line is can be rotated by hand. It only
> goes from position 'bad' to position 'aligned', it can't be rotated freely
> around. So to clarify, it can then be moved by hand back into the aligned
> position when gears five and higher again work fine.

I'm not really an expert on the Nexus 8, though I do have one (Alfine).

This dis-alignment you describe can't have too many possible causes. If
you haven't, I'd check to make sure the little retention dingus that
goes over the cable joint isn't loose, and this is a long shot, but is
the entire hub turning relative to the rear dropouts (ie, the anti-turn
washers aren't doing their job)?

If it's not that, I'd begin to suspect a problem with the internals. A
Nexus 8 is worth the rebuild, and if you can't find a local shop able to
do the job, it may be worth pulling the guts of the hub and mailing them
to a shop that can.

Sorry for the vague and unuseful advice; I hope someone else will chime
in with more particular knowledge of this problem.

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."

 

[Tvrtko Ursulin]

Andre Jute wrote:

[...snip...]

> If all else fails, you can take the Nexus 8 speed apart at home and
> service it; there are clear instructions (for the coaster version of
> this hub though) on the Lange site in Germand and English in a pdf,
> also on Sheldon Brown's site in HTML in English. If you can't find
> them, ask and I will send you the pdf by e-mail. I wouldn't try the
> repair myself though, even though I took one apart and put it together
> again successfully, and I'm no master mechanic. Thing is, the sort of
> guy who does it for a living will be able to see instantly what is
> wrong, and will have spare parts to fix it. Note that Shimano's idea
> of home service is to offer a dipping can and a bottle of oil in which
> you're supposed to soak the Nexus hub internal assembly whole for 90
> seconds; they do not actually intend amateurs to disassemble it
> further than removing the entire internal assembly as a unit. But at
> least that is a saving since you don't have to send the whole wheels
> but just the slide--out gubbins.

Thanks for the extensive list of things to check. I won't be able to dive
into it before this weekend, but after that I will let you know how it
went.

Thanks to Ryan as well.

Best regards,

Tvrtko