Singlespeed Cog won't work?

i put this cog [cs-mx66] on my self made SS, onto the splined free-wheel body,
and the chain won't run smoothly on it. Strange.

Every time i apply power, the chain slips and lifts off at the bottom the cog even though it's specified to be ok to use ?

Googled it and some forums even suggest using this cog for SS.

Any ideas ?

Are you using a 3/32" chain? Those cogs are designed for BMX (1/8") aren't they?

does that make a difference ?

i eyed the cogs up against each other and the teeth seem identical

I'm only speculating - don't really know the spec of these things, but you can't run a 3/32" chain on a 1/8" cog. The teeth are quite tall, and the chain's not going to wrap snugly around it, just sort of perch on top. Any serious oomph, and it'll slip.

Also new cog/sprocket/cassette + old chain, or vice versa, can cause slipping issues, irrespective of width.

ok cheers. Seems the forum google directed me to was wrong ! It said the cog was good to use :(

new chain, new everything, just a bad cog. Luckily it only cost £3.

So where can i get a dedicated rear cog [15t + 3/32 chain] for my converted singlespeed then ?

i can't find them anywhere :(

Those cogs are usually 3/32, but that don't mean that one is not 1/8.

Hows your chain tension and chain line post pics please of along the chain from both direction and of the side where it falls off..

I would imagine that cog is 3/32", which means it would be the right one. I think most likely situation is your chainline is super whack. How straight is it? Can you re-jig the spacers to make it better?

I've just noticed they're usually 3/32" as well. I'll let Tommy take over from here...

i use the other cog and its absolutely fine. I assume its the 1/8 cog but the sly bastards which sell them all say BMX/Singlespeed which is wrong really.

Can you measure it? Or just hold it against the chain and see whether it fits nicely or not.

Yep wrap the chain round it, if the chain sort of semi sits on top of the cog teeth it is wrong.

Seems to sit on the cog alright and your chain line looks ok from what I can see (plus you say you have run another cog on the same setup with no issues. True?). This is a picture of the problem cog yes?

Next guess is how old is the chain. If it's REALLY warn and so are your old cog and chain ring MAYBE this is causing problems. If you can measure the length as accurately as possible as you can of 12 complete links pin to pin.

Are you gearing up or down from your last setup? If the new rear cog is smaller the tighter angle the chain makes MAY make the accuracy of your chain line more important.

2nd thoughts your chain ring seems to be a bit more outboard than your rear cog, can't really tell if it's significant. Can't be sure be sit behind you bike and eye along the chain, also try with the chain off lining up the chainring and rear cog and see what you think.

A random selection of ideas there. Hope my ramblings help a bit. Let us know what you come up with.

everything seems fine as the photos show, thats why im posting here cos it's really strange.

Seems to sit on the cog alright and your chain line looks ok from what I can see (plus you say you have run another cog on the same setup with no issues. True?). This is a picture of the problem cog yes?

Next guess is how old is the chain. If it's REALLY warn and so are your old cog and chain ring MAYBE this is causing problems. If you can measure the length as accurately as possible as you can of 12 complete links pin to pin.

Are you gearing up or down from your last setup? If the new rear cog is smaller the tighter angle the chain makes MAY make the accuracy of your chain line more important.

2nd thoughts your chain ring seems to be a bit more outboard than your rear cog, can't really tell if it's significant. Can't be sure be sit behind you bike and eye along the chain, also try with the chain off lining up the chainring and rear cog and see what you think.

A random selection of ideas there. Hope my ramblings help a bit. Let us know what you come up with.

that's with the OTHER cog. Chain is spanking new. Im guessing cos i've used a smaller chain ring, from 16t to 15t, the angle is tighter, requiring more tension than the tensioner can provide. I might try a static tensioner rather than the springed ones that i currently use.

Anyway,

thanks

In that case will just removing a link work? Have you tried that?

Somebody enlighten me - can you get push-up chain tensioners, and wouldn't they work better with smaller sprockets?

ye i tried removing a link but i had to put the link back in cos the chain was just a teensy bit too short. 2mm or so, tempted to grind a few shavings of the dropouts.

Somebody enlighten me - can you get push-up chain tensioners, and wouldn't they work better with smaller sprockets?

ye you can.

Buy it then :)

such an epic effort though

and i need a half link also ^^

bear in mind you need a singlespeed or 7/8 speed 3/32 chain to use these cogs.

9 or 10 sp compact chains will not work

ye, its and 8 speed i used to have ;)