My understanding - R2R = Rim to Rim R2R2R = Rim to Rim to Rim, on my backpacking trip from North Rim to South Rim we saw MANY runners doing R2R2R. It was an event in early October.
this ultrarunner site
ultra R2R or R2R2R supports what RF says
Last edited by Harvey Lankford; 09/18/18 02:18 PM.
