Bicycle Mechanics - Thrown Chain

On my 20 min commute today I had my chain come off three times. The chain tension is fine, its a s/s so I am thinking that is is being 'guided' off the rear cog. I have a 14 tooth cog from a 7 speed shimano hyperglide cassette. The gear, cog and chain are matched. A mech at the lbs told me once that the teeth are angled to guide the chain on and off the cog when shifting. Would part or all of the problem be the teeth on the cog pushing the chain off?

flip your bike upside down and make sure it shifts ok by pedaling the bike with your hand. Switch gears to see if it changes smoothly. One thing that helps is cleaning up the cogs, chainrings and deraillures (probabily spelled that wrong) Get some of that pressurized air that comes in a can and blow it around to get anything loose out. And if you know what your doing you might want to try taking the cogs, rings and deraillures off and lubing them. Also what sort of condition is your chain in?

The chain etc., is in good condition. It is a single speed and the chainline is pretty good. I cleaned everything and lubed 2 days ago so that shouldn't be a problem. I am going to play around tonight after work and check to see if everything is straight. Any suggestions are welcome on this matter.

Hows your chainline lookin?

Is your chainline straight? The ramped cog might be more likely to chuck the chain if your alignment is off.

The chainline is pretty good. It is the first thing I am going to check when I get in from work. I realigned it when I switched from 32t to 42t and it ran better. Is the ramped cog the most likely reason?

On my 20 min commute today I had my chain come off three times. The chain tension is fine, its a s/s so I am thinking that is is being 'guided' off the rear cog. I have a 14 tooth cog from a 7 speed shimano hyperglide cassette. The gear, cog and chain are matched. A mech at the lbs told me once that the teeth are angled to guide the chain on and off the cog when shifting. Would part or all of the problem be the teeth on the cog pushing the chain off?

If it's coming off of the smallest cog, my guess is that you need to:
1. Dial in a little more tension (1/4 turn) on your shift cable.
2. Dial in your high gear limit screw about 1/4 to 1/2 turn.

If it's coming off of the smallest cog, my guess is that you need to:
1. Dial in a little more tension (1/4 turn) on your shift cable.
2. Dial in your high gear limit screw about 1/4 to 1/2 turn.

No shifters, no ders, its a single speed. Thanks for the advice. One time I can choose to ignore someones advice and not get screwed later ;)

Line is good, tension is good, sounds like the cog to me. Now if you got cables on your SS that could be the problem. <grin>

Line is good, tension is good, sounds like the cog to me. Now if you got cables on your SS that could be the problem. <grin>

Cable TV count?

your chain tension is not right if your chain pops off, especially if it comes off three times. tighten that thing up.

I examined the chain at home last night, and the links where I cut the chain to shorten it were so stiff that they were sticking in a v shape, loosened them up and no more problems. Thanks to all.

Check to see of your chain ring is true. If not, try bending it back into place with an adjustable wrench.