I live and ride in Orange County, CA... did the N Rim 2 years ago (with Western Spirit) and had a ball! I took my own bike (Santa Cruz Superlight) and didn't change out the tires (Kenda Nevegals). The trails are so varied that it was good to have a wider, all around tire. The Kendas did well through water, over rocks (lots of baby head and rocky drop offs), sands, loose gravel etc. I can recommend them but tires like saddles and pedals are really personal preference.

PS did Arizona Trail (my favorite) two days and Rainbow Rim 3... where are you riding? I thought parts of the Rainbow Rim Trail were alittle over my head. Lots of steep, narrow climbs with sharp drop offs. Lots of loose gravel and shale... but beautiful. The views were stellar!!!