Chain falling off hub bike

RoadRider400

Some bloke that likes cycling alone
I have owned a hub bike for about 3 years and it was second hand when I got it. What is the usual reason for a chain that comes off every 15 miles or so? Luckily my commute is 2 miles so its not that annoying, but I would like to fix if its easy.
 
Bent / worn chain rings ( the big one (s) up front)
 

Sharky

Guru
Location
Kent
How much slack is there in the chain? How much can you raise the chain at the mid point between the chain ring and rear sprockets?
Should be about an inch to 1 1/2 inches. If too much slack, going over bumps could throw the chain.
 
What is the chain tensioning system?
Horizontal dropouts, eccentric bottom bracket, spring tensioner?
If the chain and sprockets are not worn out, just tighten up the chain.
If you run out of adjustment replace a link with a half link.
 
OP
OP
RoadRider400

RoadRider400

Some bloke that likes cycling alone
Thanks for the advice so far. I will post photos soon, sounds like it could be a few things.

Should also add the rear nut on the chain side keeps coming loose. I am tightening it after each ride. Only one revolution or so, but there is something not quite right.
 
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Thanks for the advice so far. I will post photos soon, sounds like it could be a few things.

Should also add the rear nut on the chain side keeps coming loose. I am tightening it after each ride. Only one revolution or so, but there is something not quite right.
The axle nut should never 'come loose' sounds like a problem with the 'cone nut' on the wheelbearings to me, if you're not confident take it to a bike shop.
 

Cycleops

Guru
Location
Accra, Ghana
If the bike was second hand when you got it and it sounds like it's gone three years without attention I think it's probably overdue for service items like chain and drive sprockets etc.
If you're not equipped to do this yourself run it into your local bike shop for an appraisal.
Welcome to the forum.
 
OP
OP
RoadRider400

RoadRider400

Some bloke that likes cycling alone
Photos now posted in my media. I need to register on a file sharing website, will do that soon.

Any comments on the photos would be much appreciated.

In before 'bike needs a clean'

Thanks
 

Pat "5mph"

A kilogrammicaly challenged woman
Moderator
Location
Glasgow
I need to register on a file sharing website, will do that soon.
Hi @RoadRider400, just click on "upload a file", bottom right of your reply box.
 
OP
OP
RoadRider400

RoadRider400

Some bloke that likes cycling alone
Ok thanks
try this.
 

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OP
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RoadRider400

RoadRider400

Some bloke that likes cycling alone
Having just gone out to have a look I must agree. Thing is the chain usually falls off the back ring which doesnt seem in terrible nick.
the chain is quite a lot slacker than my road bikes, could that be the issue? It isnt terribly slack to look at (not drooping) but I can lift the top of the chain about 4cm upwards, which is more than the road bike which has a new chain.
As I have the two bikes I am happy to try some DIY, just need to know what I should replace.
 

Threevok

Growing old disgracefully
Location
South Wales
I can't see the rear cog (or state of the chain) from those pics, but if they have done as many miles as that front ring, I wouldn't be surprised if you would need to replace them too

Chain tension (or lack thereof) is probably the main cause of the chain coming off though

If you are replacing, do the lot including the chain
 

silva

Senior Member
Location
Belgium
If the rear nut loosens by itself repeatedly after retensioning it, likely the thread of the nut is damaged. And/or the thread on the axle, although the axle thread is typically stronger than the nut material, on purpose, because an axle is alot more expensive than a nut.
Even the frame dropout alu could be fretted out due to numerous retensionings, which is harder to solve.
I had such situation on a previous bike, and I could solve it along a longer axle with more thread on it, to allow a couple washers-spring ring, the spring ring at the side of the frame, the washers (flat) at the side of the nut, so the nut could be tensioned without fretting in the dropout.
Lube the spring ring well to avoid corrosion and subsequent breakdown
 
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GuyBoden

Veteran
Location
Warrington
If the rear nut loosens by itself repeatedly after retensioning it, likely the thread of the nut is damaged. And/or the thread on the axle, although the axle thread is typically stronger than the nut material, on purpose, because an axle is alot more expensive than a nut.
Even the frame dropout alu could be fretted out due to numerous retensionings, which is harder to solve.
I had such situation on a previous bike, and I could solve it along a longer axle with more thread on it, to allow a couple washers-spring ring, the spring ring at the side of the frame, the washers (flat) at the side of the nut, so the nut could be tensioned without fretting in the dropout.
Lube the spring ring well to avoid corrosion and subsequent breakdown

Yes, the nuts on those Nexus/Alfine rear hubs are easy to strip.......

The rear axle on a Nexus/Alfine is an integral part of the gear hub mechanism, so not easy to replace.....

nexus.gif
 
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