single speed chain coming off

mroli

Hi - any tips would be really welcome.

I ride a Boardman Road Comp SC to commute on. It has a Truvativ elita crankset and a flip flop rear wheel. I am riding the bike single speed and am having a problem where the chain seems to be coming off between the cog and the wheel at the back. This is then causing the chain to ship at the front.

I have had a look at the chainline and it appears to be straight, but I guess it can't be if it is shipping at the back.

As it is going between wheel (ie spokes) and cog, I'm assuming that I could "adjust" the position of the rear cog by unscrewing the track nut on the rhs and tightening the lhs? I can't adjust the crank I guess as it is a GXP and therefore "set" in position.

Any tips gratefully received.

Ta

M

Monty Dog

The reasons for your chain coming off are either incorrect chainline, insufficient chain tension or a bent frame. Assuming you haven't modified/crashed your bike since new, then I'll dismiss the latter and I'd assume chainline is correct - I doubt you need to adjust the rear hub/sprocket unless something's gone wrong. The chain needs to be fairly tight i.e. no slack to prevent it skipping off the teeth of the sprocket / chainring - there should be no more than 1cm up and down play in the middle of the chain - if not, slacken the rear wheel axle nuts, push it back and retighten - I slacken the nuts, push my hand between the tyre and seattube, roll it forward for pressure and retighten. Some people like to keep the chain bar-tight, but unless you've got a perfectly aligned and tuned drivetrain, it tend to be noisier IME. If that doesn't work, suggest a trip to your LBS for a diagnosis.

Butterd2

^^^^^ Wot he said.

mroli

Thanks Monty - I tried tightening the chain line, but I'm guessing that must be the problem as by eye, the chainline seems pretty straight. Will have a crack at tightening - nice tip about the tyre/seattube, thanks.