technodup":1gtwl8w5 said:
Whack your normal chain on and run it through an old mech. Tensions the chain and costs nothing.
+1. I can't believe that nobody mentioned this sooner in the thread.
Converting a singlespeed bike doesn't need to be complicated or expensive, and doesn't need to involve measuring chainstay lengths and/or chain lengths. I prefer things to be kept simple. Why shell out for a specific chain tensioner when the mech probably does the job better?!
In my opinion, the mech looks better as well, because it looks like it's supposed to be there. Some chain tensioners just look fecking ugly.
I've run a few bikes as singlespeeds using a single cog on the back and my rear mech as the tensioner (after all, that's pretty much all they are anyway).
Just thread the barrel end of an old bit of brake cable through the mech, move the mech so that it sits under the sprocket, and clamp the other end up nice and tight. The barrel end of the cable then sits in the mech adjuster, and the mech can be fine tuned.
Pop the chain on and pull it together so that the mech is in tension. Remove the relevant number of links and rejoin the chain.
You now have a singlespeed.
As I said, I've run a few bikes this way and have never, ever had a chain come off, nor have I ever had to re-adjust the mech to take up the slack in the chain, as is sometimes the case with chain tensioners as they can slip.