I did the R2R in May, 2013. It sure seemed easier to me than Whitney. Something about a slow climb out of the heat into cooler air. Those pounding miles at the end of the day on the Main Whitney Trail seem to get to me.
I trained by doing a Four-Mile-Panorama Trail hike in Yosemite 2 weeks before, then a Happy Isles to Clouds Rest + Half Dome and back 1 week before. That mileage and elevation was similar to the R2R, so once I did that, I knew I was good for Grand Canyon.
I left about 4:30 AM, made it to the Colorado by 9 or 10. Toughest part was the hot slog up to Cottonwood Camp from the river. After that, it cooled down and temps were pleasant. Of course that was in May.
Best part was the car swap before the hike, and key-swap at Ribbon Falls. My car was waiting for me at the North Rim. I drove to Mesquite NV that night before stopping for the night.
Here's the TR:
Grand Canyon Rim-to-Rim day hike
