Nexus 8 hub - chain falling off

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Just loosen the wheel nuts and slide the wheel back. If there is a rear
drum brake with a reaction arm bolted to the chainstay you will need to
loosen this first and retighten it afterwards - same goes for the rear
brake cable.

The chain on a hub gear bike should have some just-visible sag, unlike a
fixie which should have the chain as tight as possible without binding.

If you have an MTB chainring with cutouts for shifting (Halfords are
guilty of fitting one of these on the Subway 8) replacing it with a
plain chainring intended for singlespeed will reduce the risk of a
thrown chain substantially.

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Just loosen the wheel nuts and slide the wheel back. If there is a rear
drum brake with a reaction arm bolted to the chainstay you will need to
loosen this first and retighten it afterwards - same goes for the rear
brake cable.

The chain on a hub gear bike should have some just-visible sag, unlike a
fixie which should have the chain as tight as possible without binding.

If you have an MTB chainring with cutouts for shifting (Halfords are
guilty of fitting one of these on the Subway 8) replacing it with a
plain chainring intended for singlespeed will reduce the risk of a
thrown chain substantially.

On Mon, 15 Nov 2004 17:45:42 GMT, Mike Watson <[email hidden]>

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

The right-hand (chain side) axle nut is loose.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

On Mon, 15 Nov 2004 17:45:42 GMT, Mike Watson <[email hidden]>

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

The right-hand (chain side) axle nut is loose.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

6 x 4 x 5 x 10 =1200 km's : adjust the chain!

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped
bike. 2 or more times a day the chain will fall off, not quite
what I was expecting on a 6 month old bike which averages
around 6 miles of easy communting a day.

Chain looks loose but the back wheel doesnt look like its
moved. SUrely one of the advantages on this kind of kit is
that the chain doesnt stretch as much as a standard
derailleur?

Any ideas, reluctant to return to the shop I bought it from as
my knowledge of hub gears is probably greater than theirs.

I had a few such incidents with my SRAM S7 internal-gear hub in
the early days.

You need to keep the chain tension reasonably correct - see
http://www.parktool.com/repair_help/chaintension.shtml

The other important part of the story is to keep the chain
_clean_ and lubricated, so that readjustment isn't required too
often. Don't lubricate a chain unless you clean it thouroughly
first (especially the insides). I now use two chains - one on
the bike while the other is being cleaned, dried, lubricated
and stored ready for its next use.

John

Zog The Undeniable said:

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Just loosen the wheel nuts and slide the wheel back. If there is a rear
drum brake with a reaction arm bolted to the chainstay you will need to
loosen this first and retighten it afterwards - same goes for the rear
brake cable.

The chain on a hub gear bike should have some just-visible sag, unlike a
fixie which should have the chain as tight as possible without binding.

If you have an MTB chainring with cutouts for shifting (Halfords are
guilty of fitting one of these on the Subway 8) replacing it with a
plain chainring intended for singlespeed will reduce the risk of a
thrown chain substantially.

Hmm, it is a halfords model.

John Henderson said:

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped
bike. 2 or more times a day the chain will fall off, not quite
what I was expecting on a 6 month old bike which averages
around 6 miles of easy communting a day.

Chain looks loose but the back wheel doesnt look like its
moved. SUrely one of the advantages on this kind of kit is
that the chain doesnt stretch as much as a standard
derailleur?

Any ideas, reluctant to return to the shop I bought it from as
my knowledge of hub gears is probably greater than theirs.

I had a few such incidents with my SRAM S7 internal-gear hub in
the early days.

You need to keep the chain tension reasonably correct - see
http://www.parktool.com/repair_help/chaintension.shtml

Thanks for the link, puts it all into perspective now!

On Mon, 15 Nov 2004 17:45:42 GMT, Mike Watson <[email hidden]>

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Cheers.

Thanks everyone whose posted, some good suggestions to try out
tomorrow. I'll go for adjusting the tension first.

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.
Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?
Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Your chain is too loose. You will need to get it tight again. You can
do this yourself. Loosen the nuts holding the wheel in place. Then evenly
pull it hand taut. While holding it in this position use your third hand
to tighten the nuts. 🙂 Obviously it is easier to do if you have a helper.
If you have the roller brake, you may have to adjust it after you do this.
------------
Alex

Quoted message said:

Your chain is too loose. You will need to get it tight again. You can
do this yourself. Loosen the nuts holding the wheel in place. Then evenly
pull it hand taut. While holding it in this position use your third hand
to tighten the nuts. 🙂 Obviously it is easier to do if you have a helper.

there's a much easier way that trackies and fixed gear riders use. Loosen both
axle nuts and slide the wheel back. Tighten the non drive side and bracing
your hand against the chainstay move the rim to the right-drive-side until the
chain is at the correct tension. Tighten the drive side nut. The wheel is now
cocked in the frame. Loosen the non drive side, center it and tighten the non
drive side. Voila, correct chain tension and a centered wheel. This is easier
to do than write.
Phil Brown

Mike Watson said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.

Wait. After it falls off, do you just slip it back on? Wrong. If you
can put it back on without moving the rear wheel, then it can fall off.

Pull the wheel back in the slots (after loosening the nuts) until the
chain is nearly taut. There should be no position as you test-turn the
cranks where the chain binds, but it should also not be loose enough so
that it sags, and certainly not so loose that it can fall off.

Quoted message said:

SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Chains don't really stretch. That is, parts don't actually get longer.
In time, wear will loosen the fit between pins and rollers so that 12
full lengths will measure more than 12". This takes about the same
amount of time with either a deraileur chain, or a chain like yours, or
even a 1/8" 3-speed type chain.

The only thing about a derailleur bike that would lessen chain life is the
chainline, which should be perfect on your bike, but is not with a
derailleur. Check your chainline though, that can also contribute to
dropped chains (lay a straightedge along the chainring, it should form a
line that comes back to the same side of the sprocket. Anything more
than a few mm off is a problem.

Quoted message said:

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

You're not going to get any warrantee replacements here. You might there.
Also, you may be undervaluing their expertise.

--

David L. Johnson

__o | "What am I on? I'm on my bike, six hours a day, busting my ass.
_`\(,_ | What are you on?" --Lance Armstrong
(_)/ (_) |

David L. Johnson said:

The only thing about a derailleur bike that would lessen chain life is the
chainline, which should be perfect on your bike, but is not with a
derailleur. Check your chainline though, that can also contribute to
dropped chains (lay a straightedge along the chainring, it should form a
line that comes back to the same side of the sprocket. Anything more
than a few mm off is a problem.

If it's the bike I think it is, the chainline is perfect - it runs
absolutely silently.

On Mon, 15 Nov 2004 17:45:42 GMT, Mike Watson <[email hidden]>

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.

Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?

Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Cheers.

Thanks again everyone. Unfortunately work got in the way of having a
good look at it today.

Whilst on the subject how do you adjust the cones in these systems?

David L. Johnson said:

You're not going to get any warrantee replacements here. You might there.
Also, you may be undervaluing their expertise.

Hmm, it took a bit of convincing that they even did sell this model
last time I spoke to them.

On Mon, 15 Nov 2004 16:59:53 -0500, Alex Rodriguez <[email hidden]>

Quoted message said:

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off, not quite what I was
expecting on a 6 month old bike which averages around 6 miles of easy
communting a day.
Chain looks loose but the back wheel doesnt look like its moved.
SUrely one of the advantages on this kind of kit is that the chain
doesnt stretch as much as a standard derailleur?
Any ideas, reluctant to return to the shop I bought it from as my
knowledge of hub gears is probably greater than theirs.

Your chain is too loose. You will need to get it tight again. You can
do this yourself. Loosen the nuts holding the wheel in place. Then evenly
pull it hand taut. While holding it in this position use your third hand
to tighten the nuts. 🙂 Obviously it is easier to do if you have a helper.
If you have the roller brake, you may have to adjust it after you do this.
------------
Alex

Alex (and others who suggest this). I took a look at it this evening
and have found that the axel is held in place with what shimaon call
"non turn washers". I can see why they've dont this but it does mean
that I cant pull the wheel any further back!

The shimano docs are here(the table in section 2) :-
http://www.shimano-europe.com/cycling/phpimages/productserie/service_pdf/SI-34R0B-EN.pdf

I imagine the only way round this is to fit conventional washers?

Quoth Mike Watson:

Quoted message said:

Quoted message said:

Quoted message said:

I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
more times a day the chain will fall off...
Chain looks loose but the back wheel doesnt look like its moved.

Alex Rodriguez said:

Quoted message said:

Your chain is too loose. You will need to get it tight again. You can
do this yourself. Loosen the nuts holding the wheel in place. Then evenly
pull it hand taut. While holding it in this position use your third hand
to tighten the nuts. 🙂 Obviously it is easier to do if you have a helper.
If you have the roller brake, you may have to adjust it after you do this.

Quoted message said:

Alex (and others who suggest this). I took a look at it this evening
and have found that the axel is held in place with what shimaon call
"non turn washers". I can see why they've dont this but it does mean
that I cant pull the wheel any further back!

The non-turn washers have a single tab that fits into the axle slot. If
the tab prevents you from moving the axle far enough back, remove it,
rotate it 180 degrees and re-install it so the tab faces forward.

Quoted message said:

I imagine the only way round this is to fit conventional washers?

NO!! The non-turn washer is an absolutely essential part! Internal gear
hubs create reversing torques on the axle, depending on what gear you're
in. If you don't have something to keep the axle from rotating, it will
cause the axle nuts to loosen up.

Also, make sure the axle threads are lubricated, and it would be good to
have a bit of grease between the inner face of the nut and the outside
of the washer. This lubrication will allow you to get more clamping
force on the axle nut so the axle won't slip forward, with less effort
on the wrench.

Sheldon "Neck's Us" Brown
+------------------------------------------------+
| I’m currently appearing in: |
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| November 12, 13, 14 and 18, 19, 20, 21 |
| http://web.mit.edu/gsp/www |
| http://sheldonbrown.com/music.html |
+------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon Brown said:

Quoth Mike Watson:

Quoted message said:

Quoted message said:

>I've suddenly encountered problems with a nexus 8 equipped bike. 2 or
>more times a day the chain will fall off...
>Chain looks loose but the back wheel doesnt look like its moved.

Alex Rodriguez said:

Quoted message said:

Your chain is too loose. You will need to get it tight again. You can
do this yourself. Loosen the nuts holding the wheel in place. Then evenly
pull it hand taut. While holding it in this position use your third hand
to tighten the nuts. 🙂 Obviously it is easier to do if you have a
helper. If you have the roller brake, you may have to adjust it
after you do this.

Quoted message said:

Alex (and others who suggest this). I took a look at it this evening
and have found that the axel is held in place with what shimaon call
"non turn washers". I can see why they've dont this but it does mean
that I cant pull the wheel any further back!

The non-turn washers have a single tab that fits into the axle slot.
If the tab prevents you from moving the axle far enough back, remove
it, rotate it 180 degrees and re-install it so the tab faces forward.

Quoted message said:

I imagine the only way round this is to fit conventional washers?

NO!! The non-turn washer is an absolutely essential part! Internal
gear hubs create reversing torques on the axle, depending on what gear
you're in. If you don't have something to keep the axle from
rotating, it will cause the axle nuts to loosen up.

Also, make sure the axle threads are lubricated, and it would be good
to have a bit of grease between the inner face of the nut and the
outside of the washer. This lubrication will allow you to get more
clamping force on the axle nut so the axle won't slip forward, with
less effort on the wrench.

I didn't notice if the OP had ever measured his chain for wear. If
the washers prevent him from tightening the chain, then how could the
slack have come from slippage?

Sheldon Brown said:

The non-turn washers have a single tab that fits into the axle slot. If
the tab prevents you from moving the axle far enough back, remove it,
rotate it 180 degrees and re-install it so the tab faces forward.

Which is precisely what I had to do on the same bike when changing to a
38T chainring. From the OP's description it's a Carrera Subway 8.