SDMB is a member-run organization, focusing mostly on medium-paced medium-difficulty group rides rides in the Tucson area. If you want to ride locally to get some exercise and meet other mountain bikers, this is a great club to join.

SAMBA is largely run by John Pollock, a professor at the University of Arizona. The rides are typically a single weekend ride, often somewhere more remote/less traveled. The pace is typically slower, with more emphasis on exploration, enjoying nature and the outdoors.