Originally Posted by
operator
This floating came about when 9 went to 10 speed as well. Mostly when FSA for example tried to market their 9 speed cranks/chainrings as 10 speed compatible.
They were not.
The chain would skate in between the rings, notably on campy 10 speed compacts and FSA compacts. This is VERY dangerous if someone shifted coming off a stop light to lose the entire drivetrain mid intersection.
FSA responded by redesigning their chainrings to bring them closer together. It is this *exact* problem which leads the chain to rub/hit the large ring in the smaller rear cogs on most 10 speed setups. It doesn't matter anyways, those gears are redundant.
As I remember it, FSA had a lot of problems with their 9-speed cranks too so poor shifting with them isn't a surprise. As I said, I'm using a 10-speed chain on a 9-speed Shimano Ultegra crank with absolutely no shifting problems and it never skates.
Originally Posted by
operator
Shimano 9 and 10 speed rings are speed specific. If you try and mount a 10 speed ring on a 9 speed crank shifting WILL suck. As an experiment, mount the inner ring on a double backwards. The chain will skate like a mother****er.
Well, sure, Shimano made the change from 8 to 9-speed by offsetting the small chainring's teeth to the outside to close the gap. If you reverse the small ring you will make the gap even larger than it was with 8-speed. As I mentioned twice already, I'm having no problems with a 10-speed chain on a 9-speed crank even shifting under high chain tension.