Originally Posted by
Winfried
Why does it make a difference?
In the upshift, the chain still on the smaller ring, but pressed against the larger ring, must grab a pin or tooth tip with the opening in the link, to climb up onto the larger ring. If the opening does not fall where the grab needs to occur, the chain will just continue to rub against the larger ring and the upshift will not take place. You have a potential to change where the opening in the link falls, by changing the orientation of one ring against the other, through rotation over the arms. However, if the number of teeth is a whole multiple of the number of arms, such a rotation does nothing.