Originally Posted by coelcanth
since it changes when you flip the hub, maybe the chainline isn't right
(the cogs give slightly different chainlines, they are different thicknesses)
how are you measuring your chainline ??
for a pretty darn accurate measurement
half the rear spacing - the distance from inside of rear dropout to the face of the cog - half the width of the cog
should equal
the distance from the edge of the seat tube to the face of the chainring + half the width of the chainring + half the width of the seat tube
also, maybe your chainring is not perfectly round, or not installed with the bolts tightened down evenly ?
The chainline is straight to within a millimeter...I've measured it over and over, on both sides, using the method you just described.
As for the chainring being round...I'm pretty sure it is. There are no tight spots in the chain, and the bolts are all tightened propery. The chainring spins straight and truem, and the chain engages with it smoothly. The griding effect pretty clearly is coming from the cog, not the chainring, so I don't think the chainring is the source of the problem.