Originally Posted by
NOS88
9 and 10 speed chainrings have the teeth ever so slightly farther to the right than a 6, 7 or 8 speed chainring (according to Sheldo Brown that is:
http://sheldonbrown.com/speeds.html) . Try flipping the chainring and see that that solves the problem.
Oh, that''s a neat idea.
Are you sure the 38T ring isn't just so worn that it can't properly hold the chain? By the time the teeth get pointy, it's long gone.
As far as which would be the better choice between 38T and 39T, there are two things I consider.
1. Is my low gear low enough for me?
2. Which one creates the greatest "gap fill" gearing relative to the big ring. Graph the gear inches with a log scale and see where the 38T and 39T gears sit relative to your big ring.
Yes, the 38t one isn't worn.
I'll look into those other things and ride for a while with this.