Help: Chainnoise

[Samuel Russell]

Wotcher,

I'm on a Shimano Nexus 7 with back-pedal brake.

I noticed today on the way to work that it's got an annoying "slipping"
feeling with a cracking sound in the chain every so often, particularly in
lowest gear, and also when climbing hill in any gear. Could this be chain
stretch or bad chain tension in effect?

I checked the gear teeth, and they looked fine. I also checked the chain
links, none were bent out of shape.

Any ideas on the reason and how to fix?

yours,
Sam.

[Resound]

"Samuel Russell" <samuel.russell@studentmail.newcastle.edu.au> wrote in
message news:d0qi9q$r97$1@spacebar.ucc.usyd.edu.au...
> Wotcher,
>
> I'm on a Shimano Nexus 7 with back-pedal brake.
>
> I noticed today on the way to work that it's got an annoying "slipping"
> feeling with a cracking sound in the chain every so often, particularly in
> lowest gear, and also when climbing hill in any gear. Could this be chain
> stretch or bad chain tension in effect?
>
> I checked the gear teeth, and they looked fine. I also checked the chain
> links, none were bent out of shape.
>
> Any ideas on the reason and how to fix?
>
> yours,
> Sam.
>
>
It sounds like the chain is slipping. Take another look at the rear sprocket
and the chainring (front sprocket) they may look fine but if the teeth have
an assymetrical profile, they're not. More likely is that the chain has
stretched (actually internally worn) and simply needs to be replaced. Your
local bike shop should be able to do that for you on the spot.

[Tamyka Bell]

Samuel Russell wrote:
>
> Wotcher,
>
> I'm on a Shimano Nexus 7 with back-pedal brake.
>
> I noticed today on the way to work that it's got an annoying "slipping"
> feeling with a cracking sound in the chain every so often, particularly in
> lowest gear, and also when climbing hill in any gear. Could this be chain
> stretch or bad chain tension in effect?
>
> I checked the gear teeth, and they looked fine. I also checked the chain
> links, none were bent out of shape.
>
> Any ideas on the reason and how to fix?
>
> yours,
> Sam.

Resound sounds right, but another thing it could be is that the chain is
at too much of an angle... that is, if it's not "in any gear" but rather
in a few gears... on my MTB, if I'm on the small front cog and one of
the larger back ones, or the large front one and one of the smaller rear
ones, I get some noise and occasional slippage if the tension is
changing (e.g. when I'm pedalling a bit sloppy on an uphill).

T

[Samuel Russell]

Tamyka wrote

> Resound sounds right, but another thing it could be is that the chain is
> at too much of an angle... that is, if it's not "in any gear" but rather
> in a few gears... on my MTB, if I'm on the small front cog and one of
> the larger back ones, or the large front one and one of the smaller rear
> ones, I get some noise and occasional slippage if the tension is
> changing (e.g. when I'm pedalling a bit sloppy on an uphill).

Unfortunately its a hub gear, so there's only one back sproket.

I tried changing the tension on the hub gear line to see if it was gear-line
mistension, but it seemed to change well between low and high, and sit
firmly in the selected gear.

I was going to LBS today to pick up an ordered lock, so I'll ask more there.

yours,
Sam.

[John Henderson]

Samuel Russell wrote:

> I tried changing the tension on the hub gear line to see if it
> was gear-line mistension, but it seemed to change well between
> low and high, and sit firmly in the selected gear.

With an internal-gear setup, noise from a worn sprocket will
happen after a new chain is fitted. Because the chain can't
skip, you'll just get protesting noises.

A badly worn chain might get noisy. Unless you've readjusted
the chain tension to take up the slack though, you're likely to
throw the chain off the chainring or sprocket before this.

If you've adjusted the chain too tightly, you'll likely get a
variety of noises and odd behaviour (from chain and/or hub).
See http://www.parktool.com/repair_help/chaintension.shtml for
help on adjusting chain tension.

Other than chain tension, the gear change cable might require
adjustment. See http://sheldonbrown.com/nexus.html for some
details.

John

[Samuel Russell]

John wrote some good word,
>> I tried changing the tension on the hub gear line to see if it
>> was gear-line mistension, but it seemed to change well between
>> low and high, and sit firmly in the selected gear.

I took everyone's advice and took it to LBS, who looked at it briefly.

> With an internal-gear setup, noise from a worn sprocket will
> happen after a new chain is fitted. Because the chain can't
> skip, you'll just get protesting noises.

My visual estimate was backed up, the sprocket was fine.

> A badly worn chain might get noisy. Unless you've readjusted
> the chain tension to take up the slack though, you're likely to
> throw the chain off the chainring or sprocket before this.

Chain tension also seemed to be fine, but I'm going to be watching it for
the next few weeks.

> Other than chain tension, the gear change cable might require
> adjustment. See http://sheldonbrown.com/nexus.html for some
> details.

This appears to have been the boogie! LBS switched the Nexus Inter7 into
gear 4 where two red lines on the hub's tension display should line up.
They were out of alignment: gear change cable at the wrong tension! Having
shown me how to adjust the barrel to change tension, no noise problems in
gears.

(Apart from 1 and 3 which have a bit of "whirring" noise normally, but no
extra friction).

No chain slip. Hurrah. I'd hate to be carrying load on a derailleur and
suffer from a slippery chain.

thanks for everyone's advice, I've learnt a few new tricks,

Sam.