[fuzzynutz]

I think it's due to a bad chainline, but how important is the chainline on a Singlespeed? I assume very, but can someone confirm this?

Also, what would be the remedy? It's a cruiser frame with Singlespeed Hub and old 3 piece cranks. Is it possible to adust the position of the cog on the hub?

 

[Straya]

Yeah probably chainline and yes chainline is very important for singlespeeds.

Otherwise is there any chance that something is flexing excessively? Its probably worth checking that the rear hub is properly aligned in the dropouts too. I assume that you have semi decent chain tension as well? Since you are using ramped cogs I guess this might be an issue but really it shouldn't be.

Moving your rear cog on the hub is a possibility and will depend on the brand of hub. Its quite common though for singlespeed hubs to have a few spacers on there so have a good look and see if you have spacers on there. Otherwise post some good close up photos of your hub and setup and then we can have a close look and offer any other suggestions.

 

[J-Dubs]

If the cranks came from another bike, the BB spindle length could be a issue.

 

[Wumpus]

You might also be able to move the front chainring in or out to help.

http://www.sheldonbrown.com/chainline.html#front

 

[fuzzynutz]

Thanks for all the replies. I think it was just a busted link in the chain causing the problems. So I'm going to see if the guy wants me to replace it, and hopefully that will solve the issue.

 

[stinkyboy]

You might also be able to move the front chainring in or out to help.

http://www.sheldonbrown.com/chainline.html#front

Pours a 40 out for Sheldon.