clicking cog...
 

Anybody else have a cog that clicks as the chain rolls over it?

I've been working on this for weeks... my chainline is now within 1/2 mm of perfect. As the chain rolls over the cog it clicks rather loudly, at least as noisy as my geared bikes would be. It's a SOMA 15T cog, KMC chain, Shimano 39T chainring. The chainring *does not* make this clicking sound, unlike the cog, which makes me think it's not the chainline. I've tried cleaning, lubricating, changing chainrings, changed the bottom bracket, etc.

Is this normal with a Soma cog? Anything else I should try? This is my first fixie, so I'm not really sure how loud the drivetrain should be, but I was expecting it to be nearly silent.

what's your chain tension like? super tight chains can be a bit noisy.
at least in my limited experience.

yeah, whenever my bike starts to click it ussually just ends up being an over-tightened chain. Give it a tiny bit more slack and see if that helps

That or your chainline isnt right.

...or its something that i dont know about

How's your chain stretch? Is this a new cog?

Is it a single click or constant? Which KMC chain is it? Is it a new chain and old cog or and old cog and a new chain? All new?

Wheel Doctor posted the key question. I bet you need to break it in if you have a mix of new and used components.

Moral of the story, new components need new components.

Not necessarily. New componenets need to "mesh" with old components.

No, new components need new components.

New components will "wear" to old components. Put a new cog on an old chain and that stretched chain will ramp the cog until it fits. It's meshed now, but it's not so innocuous as that word might imply.

And of course the reverse is true if you have a new chain on old cogs or chainrings.

It the meantime, untile they've mated to one another you can have some seriously sloppy chain/tooth interfaces which put you at risk of launching your chain. (A badly worn drivetrain is also at risk of this, but a mismatched drivetrain is the worst)

So, you're saying that when you replace the chain you should also replace the cog and chainring? This seems excessive.

Not quite. But when you replace the chain you really need to inspect the cog and ring to make sure that they aren't ramped. If the chain is severely stretched it's almost certain that you've trashed your ring and cog to.

I think it is the soma cog. Mine clicks too. Izumi gold v chain, perfect chainline, everything new. I am not comfortable loosening up the chain since it may come off (with serious consequences).

why would it come off it your chainline is "perfect"?
super tight chain = noise + dead bearings

A chain WILL come off if it is loose enough, no matter the chainline. The chain will flop until if comes off the cog/ring.

I'm running a Soma cog (new) and a KMC Z51 chain (new). I listened very closely today and there is a very subtle clicking, but its barely noticable. I'm very noise conscious on any bike and this is barely audable. Another thought? Will a 9spd chain work with a standard 3/32 track cog like the Soma? I have a bunch of KMC Z9000 9speed chains that I got on the cheap, but I chose the wider beefier 7 spd Z51. I had intended to use a SRAM PC-48 but didn't have one handy. Still the SOMA and Z51 seem to be just fine.

I think that I have a good feel for chain tension and a good ear. My young mechanic was working on a real poor SS with a less than happy chainline for one of his running mates. I could hear the chain binding while I was sitting reading in another room. I yelled, Loosen the chain a bit. I got in return. Mind your own business, I got a handle on it. You didn't want to work on it anyway! He was right, it was and is a piece.

Thanks for all the tips. It's a new (= month old) cog and chain, but old chainring. I've checked the chain and it hasn't worn, so I don't think the chainring is too worn. I've tried changing the chain to a brand new one, and that doesn't make the chainring click, so I don't really know what the problem is. I tried loosening up the chain tension, didn't make a difference.

I guess I'll just live with it, since there isn't anything obviously wrong other than the noise itself :)

I thought you said that it was your cog clicking?

Jude, St. Michaels, MD

Right, it IS the cog clicking. But I figured if it were a problem with unequal wear on various parts, then putting a new chain on would make the chainring click too. In any case, it didn't, and the cog still clicks. It did this from as soon as I built it, although then the chainline was off by a bit more, maybe 1.5 mm.