Singlespeed chain tension...

[dookie]

i'm quite confident that my definition of 'fairly loose' will not derail in the roughest of terrain...then again, it sounds like were not so different in our preferences.

'1/2" of slack' is about right for me, which means 1/2" of total vertical deflection...1/4" of sag, measured at the tightest point in the drivetrain revolution.

 

[MJN]

I agree with Andy R,from experiance I would say as tight as you can without it feeling like its binding.Your chain coming off downhil is a real pain,and I've had it happen with a perfect chainline and ss specific sprocket,chain,chainring but too much slack,your chain coming off uphill,ouch!

 

[Andy R]

I agree with Andy R,from experiance I would say as tight as you can without it feeling like its binding.Your chain coming off downhil is a real pain,and I've had it happen with a perfect chainline and ss specific sprocket,chain,chainring but too much slack,your chain coming off uphill,ouch!

Yeah - too right !! :cry:
If you are taking the time to adjust the chain tension it's as easy to adjust it to have no "slack" as to have, say, 1/4" of sag. Obviously even an optimally adjusted chain can be deflected at its mid-point by applying finger pressure (as can a toothed belt) but I don't think that it's a good idea to allow it to sag under gravity at all - by my thinking that's too loose.

 

[thecannibal]

AndyR, it sounds like you might've been blessed with a greater degree of drivetrain concentricity than many. Tight spots in a chain are pretty common, and can be a nightmare to get out, often necessitating the chain be pretty loose at its loosest point.

 

[Andy R]

AndyR, it sounds like you might've been blessed with a greater degree of drivetrain concentricity than many. Tight spots in a chain are pretty common, and can be a nightmare to get out, often necessitating the chain be pretty loose at its loosest point.

True - maybe I have been lucky . I have improved things by re-centering the chain ring (nip the bolts, find the tight spot and give it a tap backwards - repeat until you find the best result, then finally tighten).

This only works if you have a little play between the ring and the spider, though a few thou. movement makes a big difference.
I would add that decent machined chainrings and sprockets are better as far as concentricity goes than cheap stamped ones.