How do I stop the chain falling off

[Mussels]

I changed my chainring a while back and my chain on occasion falls off, happens much more now than it used to so I guess chain wear is much to blame. Anyway the chain isn't worn enough to change yet and I'm wondering what my options are, the Wisper came with a plastic chainring cover that attached to the 52 tooth chainwheel and did the job but I wanted a different gear setup.
I can probably find another chainring with a similar guard but I'd rather find something that can be reused. I would like a front mech on the bike but that will require too much investment to do now.
I've seen some flashy products for muntain bikes that look over engineered and cost upwards of £50, I'd rather put the chain on occasionally instead than spend that much.
Is there a sensible and cheaper answer?

 

[flecc]

Not a proper bash guard, but here's some cheap guard rings that might help if it's coming off on the outboard side. It may even be possible to mount one each side:

Chainring bash guard
.

 

[Mussels]

Thanks,
It falls off the inside, I've emailed the shop to see if I can use it there as well.

 

[Phil the drill]

Thanks,
It falls off the inside, I've emailed the shop to see if I can use it there as well.

Hi Mussels

I changed the chain ring on my wisper to a 42t (and the rear cassette to an 11 - 34t) and had exactly the same problem. Chain always fell off on the inside, particularly in the high gears. The problem is the angle of the chain, which deviates from a straight path more than on a conventional bike due to the width of the frame (accommodating the battery). The chain guard on the original sprocket acts as a chain guide and helps to prevent this, but cannot be used when you change the chain ring. The answer I found was to undo the chain ring from the spider and refit it on the inside. The inside is stepped, similar to the outside, so the chain ring is nicely supported by the spider as well as the bolts. The bolts may have to be changed dependent on the type chain ring fitted, but basically it's a simple modification. The straightening in the chain path achieved by doing this has almost completely cured the tendency of the chain to fall off (it has happened twice in the 9 months since I did this, as opposed to every trip before I did it!). Obviously you may have to adjust the chain length too if you've fitted a different size chain ring (- shortening for a smaller ring) - how much depending on the size of the ring.

Cheers, Phil

PS. It's the cheapest option too! Worth a try before buying any extras

 

[Mussels]

Hi Mussels

I changed the chain ring on my wisper to a 42t (and the rear cassette to an 11 - 34t) and had exactly the same problem. Chain always fell off on the inside, particularly in the high gears. The problem is the angle of the chain, which deviates from a straight path more than on a conventional bike due to the width of the frame (accommodating the battery). The chain guard on the original sprocket acts as a chain guide and helps to prevent this, but cannot be used when you change the chain ring. The answer I found was to undo the chain ring from the spider and refit it on the inside. The inside is stepped, similar to the outside, so the chain ring is nicely supported by the spider as well as the bolts. The bolts may have to be changed dependent on the type chain ring fitted, but basically it's a simple modification. The straightening in the chain path achieved by doing this has almost completely cured the tendency of the chain to fall off (it has happened twice in the 9 months since I did this, as opposed to every trip before I did it!). Obviously you may have to adjust the chain length too if you've fitted a different size chain ring (- shortening for a smaller ring) - how much depending on the size of the ring.

Cheers, Phil

PS. It's the cheapest option too! Worth a try before buying any extras

Thanks but I did that when I first fitted it, it has been OK most of the time and only coming off every 500 miles or so but since the weekend it's coming off every 10 miles or less. It's happening when I ease off in top gear which makes me thing the chain is going slack when I stop pedaling.
The weekend work is significant as the gear change was getting sluggish and had got clogged up with road salt and other sludge so I dismantled the cage, cleaned and regreased the pulleys and then gave the chain a good clean. I have a feeling the resistance the dirty parts gave previously was stopping the chain going slack at the top and jumping off the chainwheel. Ideally I should change all of the worn components but I reckon there is a good thousand miles left in them yet as long as I can fit a plate to the inside.
Thinking about it now it won't be too hard to fabricate something myself. I have double length chainring bolts and can use the chainring as a template, all I need is some rigid plastic that I can cut up.
Then I need to remember to deburr it so I don't lacerate my leg next time I fall off. I do hope the link Flecc found say their product will work as I'm feeling lazy and would like to blame someone else if it goes wrong.

 

[torrent99]

Thanks but I did that when I first fitted it, it has been OK most of the time and only coming off every 500 miles or so but since the weekend it's coming off every 10 miles or less. It's happening when I ease off in top gear which makes me thing the chain is going slack when I stop pedaling.

Phil's already mentioned it but you did shorten the chain when you changed to a smaller ring didn't you?

 

[Mussels]

A search of the net seems to suggest the chain is too loose, time now to find out if it's a derailer adjustment required or if I should shorten the chain. I'll be quite happy when I get rid of the waste of space megarange gear and fit my sun tours freewheel.

 

[Mussels]

Phil's already mentioned it but you did shorten the chain when you changed to a smaller ring didn't you?

Sorry I didn't answer this before, I did shorten the chain when I changed the chainring and it has done a couple of thousand miles since without problem.