It's because Surly cogs have those big dumb square teeth.

Thats what the master link or quick pin link is for, And if you do it right, Nothing happens.

I was looking at the scrod cog. What exactly is the difference? Looks kinda just like the Surly. And I'd love a DA cog, but they only go to 16t, and I need 17.

Why don't you PM Scrod ? I'm sure he can tell you. Also, Somas go from 17 to 21 teeth, and are great cogs as well.

Ok, great. Thanks for the advice everyone.

Arent surly's cogs a little taller then the average to prevent dechain

That would make sense as to why my chain isnt wanting to "let go" so to speak, causing a bit off an off rotation.

them's fightin words...

Im glad I found this thread. Ive been running a 18T surly cog/sram pc-1 combo for years with no noise issues. I recently switched to wipperman chain and now I get a ton of chain noise off the rear cog. I didnt even think about the cog. If I flip the bike over and spin the cranks, you can tell that the noise is coming from the rear.

I can tell you that surly cogs are quiet with SRAM chains. Dont throw out the surly cogs, just run a PC-1 with it. If you have wipperman expect noise. The wipperman side plates are much larger than the PC-1 I guess that is why its noisy with the square teeth....

On another note, my surly 18 tooth cog has squared off teeth, my 19T surly is more pointy - go figure.... Might take a dremel to round off the corners of the square tooth. My Euro asia 17t has pointy teeth too..

Well I took a grinding wheel to the sharp corners of the squared off surly teeth and I think I did the trick. The cog is smoother with the chain. I finished off the sharp edges with a file to smooth them out. Sorry for the grainy pic.

You should expect some noise any time you put a new chain on a used cog.

bang. last reply hit it.
look...work your own diagnostics, but...

you need to make sure its not a chain link.
otherwise, your components may not match. in other words, chains stretch and cogs/chainrings wear. if they aren't matching, it may take some time to mesh...or if its bad enough, it just won't work

we're so glad you're back.