SRAM Red 53/39 10spd rings and 172.5 crank work with 11 speed cassette upgrade? I want to upgrade my 10 speed to 11. Will my SRAM Red 53/39 10spd rings and 172.5 crank work with an 11 speed upgrade? Looking to upgrade to SRAM eTap with the "kit". I understand the need for a new cassette (11-28), front &amp; rear derailleurs, shifters and 11 speed chain.  Do I need new crank and chainrings?
11-speed chain is narrower than 10-speed. You keep the crank but you must put on 11-speed rings which will most certainly fit judging by the pictures on SRAM's website. The shape of the cranks remains the same and the BCD is identical, of course.