Ten-speed chainrings can be installed on an 11-speed crank, just as 11-speed chainrings can be installed on a 10-speed crank. The spiders are identical. However, all of our groups are designed to function as complete groups, so if a 10-speed crank is installed in an 11-speed group or vice versa, we strongly recommend changing to the appropriate chainrings. Ten- and 11-speed should not be mixed.
Our 22 groups actually have the chainrings slightly farther apart than our 10-speed groups, in order to ensure that all cogs can be safely reached in the small ring, and the chain and front derailleur are specifically designed to work with that gap. Running a 10-speed chain on 11-speed rings or an 11-speed chain on 10-speed rings could cause chain jams or derailments.
So yes, purchase the power meter of your choice, knowing that it will still be usable when you go 11-speed, but make sure you have 10-speed rings on it when you run it with a 10-speed group.
—Dan Lee
Public relations specialist, road and cyclocross, SRAM/Zipp/Quarq
Read more at
http://velonews.competitor.com/2013/11/b...u3jpUBeoCX0w.99