Nexus 8 speed maintenance

[dalek]

I was wondering if anyone out there knew much about the internal workings of
Nexus 8 speed hubs?

I have one on my commuter bike that has done around 10,000 km with a
clydesdale class rider (100kg+) on board. This hub has now lost its 5th
gear, where it slips quite frequently when under any sort of load.

The problem first developed a while back when it would slip under extreme
load, such as taking off from a stand still, but never at other times (until
recently), so using another gear for the standing starts avoided the problem
for quite some time. It doesn't slip in any other gear as far as I know.
This is particularly a problem as 5th gear is the 1:1 ratio and gets used
around 25% of the time with my current sprockets.

I have got a copy of the relevant service manual from Sheldon's site (
http://sheldonbrown.com/nexus8/ ) and acquired the 2 key specialist tools
needed for disassembly/reassembly along with some of Nexus hub grease. I
have then pulled the hub apart and inspected its guts.

Inspection has revealed no cogs/gears with any sign of wear or damage. The
only issue that seemed apparent was the cog that is part of the axle
assembly appeared to be a little crooked wrt the axle itself I made an
attempt to straighten this and got it fairly close to what appeared to be a
normal alignment.

I then reassembled the hub using liberal amounts of the Nexus grease and
having no parts left over. Everything worked as before except,
unfortunately, the problem remains, although at this stage, not quite as bad
as before - that is, it seems to take a bit more torque to get it to slip.

So it is possible the axle/cog issue identified may be the cause of the
troubles, but alternatively, the service may have been responsible for the
slight improvement in the problem with the real cause of the problem being
quite separate from this.

Given this, I would be interested know if anyone else is familiar with such
a problem (loss of just the 5th gear) and its possible causes. Would the
axle/cog issue identified seem like a plausible explanation? If this is the
likely problem, would it be worth replacing this component, or just buying a
new hub? Eg, how would the price of an axle assembly compare to the cost of
a new hub?

Any help would be much appreciated.

dale

 

[ddog]

That's the 'catch' about those marvels. I almost wanted one of those
with 8 speed
Red dot Nexus specials with
totally enclosed chainguards. But the rear tires don't change too
easily
and the gear cluster hubs are supposed to be real complex.

Other than that, they sound like a dream.

For as reasonable as LBS labor is, I'd take it there in a heartbeat (to
their 'top gun'' wrench to work on).
I'd do my learning that way. I generally don't like to learn on my
vehicles when they break down and I don't have a clue, but you already
sound like you've been in it before.


Good luck.



dalek wrote:
> I was wondering if anyone out there knew much about the internal workings of
> Nexus 8 speed hubs?
>
> I have one on my commuter bike that has done around 10,000 km with a
> clydesdale class rider (100kg+) on board. This hub has now lost its 5th
> gear, where it slips quite frequently when under any sort of load.
>
> The problem first developed a while back when it would slip under extreme
> load, such as taking off from a stand still, but never at other times (until
> recently), so using another gear for the standing starts avoided the problem
> for quite some time. It doesn't slip in any other gear as far as I know.
> This is particularly a problem as 5th gear is the 1:1 ratio and gets used
> around 25% of the time with my current sprockets.
>
> I have got a copy of the relevant service manual from Sheldon's site (
> http://sheldonbrown.com/nexus8/ ) and acquired the 2 key specialist tools
> needed for disassembly/reassembly along with some of Nexus hub grease. I
> have then pulled the hub apart and inspected its guts.
>
> Inspection has revealed no cogs/gears with any sign of wear or damage. The
> only issue that seemed apparent was the cog that is part of the axle
> assembly appeared to be a little crooked wrt the axle itself I made an
> attempt to straighten this and got it fairly close to what appeared to be a
> normal alignment.
>
> I then reassembled the hub using liberal amounts of the Nexus grease and
> having no parts left over. Everything worked as before except,
> unfortunately, the problem remains, although at this stage, not quite as bad
> as before - that is, it seems to take a bit more torque to get it to slip.
>
> So it is possible the axle/cog issue identified may be the cause of the
> troubles, but alternatively, the service may have been responsible for the
> slight improvement in the problem with the real cause of the problem being
> quite separate from this.
>
> Given this, I would be interested know if anyone else is familiar with such
> a problem (loss of just the 5th gear) and its possible causes. Would the
> axle/cog issue identified seem like a plausible explanation? If this is the
> likely problem, would it be worth replacing this component, or just buying a
> new hub? Eg, how would the price of an axle assembly compare to the cost of
> a new hub?
>
> Any help would be much appreciated.
>
> dale

 

[M-gineering]

ddog wrote:

>
> For as reasonable as LBS labor is, I'd take it there in a heartbeat (to
> their 'top gun'' wrench to work on).

nexus-8 repairs generally consist of replacing the complete internal unit!

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

 

[dalek]

"M-gineering" <[email protected]> wrote
> ddog wrote:
>> For as reasonable as LBS labor is, I'd take it there in a heartbeat (to
>> their 'top gun'' wrench to work on).

This is probably reasonable advice for most, but I do ok on the mechanical
side and I have had more experience with the nexus 8 speed than any of the
local mechanics I know. None of the ones I know have pulled a hub apart and
put it back together again, so why would I pay someone like this to make a
mess of my hub?

> nexus-8 repairs generally consist of replacing the complete internal unit!

I was a bit worried about this, as it would come at a cost close to
replacing the whole hub. It would have the advantage that you wouldn't need
to rebuild the wheel, at least. But looking at the service manual, it would
seem to imply there are some major sub-assemblies that could be replaced
separately, and the manual seems oriented around breaking it down into these
sub-assemblies. Unfortunately, it doesn't give much help in determining
whether any of these parts need replacing or not.

dale

 

[M-gineering]

dalek wrote:
> "M-gineering" <[email protected]> wrote
>> ddog wrote:
>>> For as reasonable as LBS labor is, I'd take it there in a heartbeat (to
>>> their 'top gun'' wrench to work on).
>
> This is probably reasonable advice for most, but I do ok on the mechanical
> side and I have had more experience with the nexus 8 speed than any of the
> local mechanics I know. None of the ones I know have pulled a hub apart and
> put it back together again, so why would I pay someone like this to make a
> mess of my hub?
>
>> nexus-8 repairs generally consist of replacing the complete internal unit!
>
> I was a bit worried about this, as it would come at a cost close to
> replacing the whole hub. It would have the advantage that you wouldn't need
> to rebuild the wheel, at least. But looking at the service manual, it would
> seem to imply there are some major sub-assemblies that could be replaced
> separately, and the manual seems oriented around breaking it down into these
> sub-assemblies. Unfortunately, it doesn't give much help in determining
> whether any of these parts need replacing or not.
>
> dale
>
>
There is a list of faults and parts to replace, but your problem isn't
mentioned. BTW there is no 1:1 ratio, gears are always used

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

 

[A Muzi]

> dalek wrote:
>> I was wondering if anyone out there knew much about the internal workings of
>> Nexus 8 speed hubs?
>>
>> I have one on my commuter bike that has done around 10,000 km with a
>> clydesdale class rider (100kg+) on board. This hub has now lost its 5th
>> gear, where it slips quite frequently when under any sort of load.
>>
>> The problem first developed a while back when it would slip under extreme
>> load, such as taking off from a stand still, but never at other times (until
>> recently), so using another gear for the standing starts avoided the problem
>> for quite some time. It doesn't slip in any other gear as far as I know.
>> This is particularly a problem as 5th gear is the 1:1 ratio and gets used
>> around 25% of the time with my current sprockets.
>>
>> I have got a copy of the relevant service manual from Sheldon's site (
>> http://sheldonbrown.com/nexus8/ ) and acquired the 2 key specialist tools
>> needed for disassembly/reassembly along with some of Nexus hub grease. I
>> have then pulled the hub apart and inspected its guts.
>>
>> Inspection has revealed no cogs/gears with any sign of wear or damage. The
>> only issue that seemed apparent was the cog that is part of the axle
>> assembly appeared to be a little crooked wrt the axle itself I made an
>> attempt to straighten this and got it fairly close to what appeared to be a
>> normal alignment.
>>
>> I then reassembled the hub using liberal amounts of the Nexus grease and
>> having no parts left over. Everything worked as before except,
>> unfortunately, the problem remains, although at this stage, not quite as bad
>> as before - that is, it seems to take a bit more torque to get it to slip.
>>
>> So it is possible the axle/cog issue identified may be the cause of the
>> troubles, but alternatively, the service may have been responsible for the
>> slight improvement in the problem with the real cause of the problem being
>> quite separate from this.
>>
>> Given this, I would be interested know if anyone else is familiar with such
>> a problem (loss of just the 5th gear) and its possible causes. Would the
>> axle/cog issue identified seem like a plausible explanation? If this is the
>> likely problem, would it be worth replacing this component, or just buying a
>> new hub? Eg, how would the price of an axle assembly compare to the cost of
>> a new hub?

ddog wrote:
> That's the 'catch' about those marvels. I almost wanted one of those
> with 8 speed
> Red dot Nexus specials with
> totally enclosed chainguards. But the rear tires don't change too
> easily
> and the gear cluster hubs are supposed to be real complex.
>
> Other than that, they sound like a dream.
>
> For as reasonable as LBS labor is, I'd take it there in a heartbeat (to
> their 'top gun'' wrench to work on).
> I'd do my learning that way. I generally don't like to learn on my
> vehicles when they break down and I don't have a clue, but you already
> sound like you've been in it before.

We've found the SRAM Sevens to be hardier then the various Nexii -
quicker, cleaner wheel change too.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[dalek]

"A Muzi" <[email protected]> wrote in message
news:[email protected]...
> ddog wrote:
>> That's the 'catch' about those marvels. I almost wanted one of those
>> with 8 speed
>> Red dot Nexus specials with
>> totally enclosed chainguards. But the rear tires don't change too
>> easily
>> and the gear cluster hubs are supposed to be real complex.
>
> We've found the SRAM Sevens to be hardier then the various Nexii -
> quicker, cleaner wheel change too.

The wheel change/puncture repair is a little more complicated than a
derailleur based setup, but not too bad once you get used to what you have
to do. I can imagine an enclosed chain guard would complicate things,
though, but I run mine without this addon so can't comment too much on that.

Having put about 10,000 km on mine, I have had a bit of experience with
fixing punctures when out on the bike, despite running kevlar lined tyres
that are supposed to resist penetration. I don't use the roller brake, so
this helps, so the only real extra is disconecting the gear cable and
remembering to carry a 15mm spanner (a Jethro tool seems to work well for
me).

With a bit of practice, disconnecting the gear cable is no big deal and all
up it usually takes me about something approaching 5 minutes longer to fix a
flat. This time would obviously increase if you added in a roller brake
(needs to be unbolted from the chain stay) and/or a chainguard.

I haven't looked at a SRAM setup, but have seen the Rohloff. This seems
much easier to diosconnect the gear cable than the Nexus, so I am a bit
surprised Shimano haven't managed to simplify this a bit more.

dale