I’ve been riding my first singlespeed for about 4 months now and although I’ve been enjoying it very much I have been having problems with the chain jumping off. I chose a rear cog kit with plenty of spacers so I could get the chain line right too. The chainline looks OK to me and my friends couldn’t agree on if it was out or which way it was out. I use chain tugs and have experimented with different chain tensions but it makes little difference.

Is it all about chainline and tension or are there other factors at play? How spot on does the chainline have to be?

It comes off either when I put loads of power down quickly or if I put the power down and hit a bump at the same time. I’m learning to put up with it but the first few times it happened I was usually left sprawled across my handlebars heading towards the nearest tree or river. The chain doesn’t seem to come of the same side of the cogs each time either.

Any ideas much appreciated.

it’s more to do with tension.

You might find the chain is stretching so the chain is becoming stack during the ride, either increase the tension or if possible remove another link/half link

hope this helps

Chain tension. I will be back with a YouTube link to illustrate this in a moment

Is it coming off at the back or the front?

If the latter, then do you have an SS chainring? They have longer teeth so it’s harder for the chain to come off.

Surly make some nice ones out of stainless steel; the cheapest I’ve found so far are Goldtec though (about £17 each) which seemed fine.

EDIT: if you’re really unlucky then you have cranks that are off centre. You will get the chain tension varying hugely as you turn them. The simplest fix then is some new cranks, but there are also various bodges you can do.

Watch the bit where I set the chain tension. If this does not work call or email me. Sorting this out is what we do. You may have an arsed spring, but try the technique in the vid first.

[video]http://m.youtube.com/#/watch?v=L-n0m6jMOCE[/video]

OK thanks. I find that I need to add about a quarter turn on the tugs after every 2 or 3 average length rides as the chain gets really slack. This is even after 4 months.

And what the other chap said. Tall toothed ss specific rings may help.

Proper SS chainring fixed it for me.

Thanks Charlie, handy video. The bikes an Inbred and I just use the chain tugs that On One sell. One of my mates who’s single speeded for a long time suggested putting a tensioner on like the one in your video. I think this could be the solution. My gut feeling is that when I put the power down the chain slackens due to flex in the frame and the addition of hitting a bump helps flip it off. It’s just a theory. Maybe a sprung tensioner will help take up the slack in these situations?

Proper SS frame?

Some frames flex considerably under SS use.

Otherwise as said – Surly or On-One front ring and proper SS rear cog.

Also remember a derailleur chain is designed to slip off the cog teeth, so it’s better (but not essential) to use a BMX or track chain.

All the kit is proper singlespeed stuff by the way including the chain and cogs. Having read oldnpastit’s post I’ve just had a closer look at the bike. It seems that the chain tension is not constant as I turn the crank and that the rear cog looks kind of oval as if it hasn’t been welded onto it’s ring properly. Hopefully a new rear cog will fix it. I can’t remember where that cog came from but it wasn’t Charlie the bike monger.

If you are getting slack spots in your chain, then your front ring may not be central. It’s pretty common.

Easily fixed.

Slacken chainring bolts.
Find tightest spot on chain
Gently tap front side of chainring
Spin
Still got a tight spot?
Repeat, repeat etc.
Then when the chain has constant tension lock the bolts down n

I have some real flexy steel frames and if you have…
Tall toothed rings and cogs
One speed specific chain
Chainring on true
…. Then the chain won’t come off. The frame ain’t the cause.

Thanks Charlie! I’ll have a look at it tomorrow and let you know how I get on.