How tight can the chain be?
 

I changed the gearing on my converted single speed and shortened the chain so that I don't need a chain tensioner anymore. The chain is fairly tight right now and I am concerned that it may be too tight. There is perhaps 3/4 of an inch of sway in the chain. Are there potential problems here?

Chain tension is critical on single speeds. Too loose and it keeps bouncing off. Too tight and the crank feels rough and the bike gets hard to pedal. The issue is that you never get the front chainring on so that it is perfectly concentric with the bottom bracket spindle. As a result, the chain will get tighter and looser as you turn the crank through it's entire circle.

The first thing to do is to loosen the chainring bolts so that they are just finger tight and turn the crank torough several revolutions. If you have the chainring bolts just right, the chainring will position itself so that it is nearly concentric. Now snug those puppies down. Next set the chain tension. Start with the chain tension too tight then gradually loosen it until just the point where the crank feels smooth all of the way around.

This was shown to me by a six-day race mechanic.

Install the chain so that it is just tight enough that it will not come off while spinning the cranks when the bike is mounted or held with the frame at a 90 degree difference to it's regular position.

So, you clamp(carefully and padded) the bike by the top tube in a stand and rotate the frame so it is parallel to the ground. Pedal the bike. The chain is at the correct tension when it seems like it wants to come off the chainring but won't.

Another way to check this is to pedal the bike in a stand while holding a screwdriver against the chain just behind the chainring while pedaling and trying to derail the chain. You want it set just tight enough so that it will not come off.

To the uninitiated this will seem a little loose until you get used to it.

I rent several single speed beach crusiers a day, and I try to maintain a 1/2" to 3/4" defelection in every chain.

3/4" is as much slack as you want to give your chain. That is not tight at all. I give my chains about a half inch up/down slack.

George