Start w/ a car parked at the bottom of Reddington Rd. in Tucson. Get a shuttle to Oracle.
In Oracle, ride the fire control road up the back side on Mt Lemmon, ride to the top of
the ski run, hit Meadow Trail, start the beginning of the long descent down the front side
with Aspen Draw, Sunrise, Mt Bigelow, Green Mtn, Bug Spring, Prison Camp, Molino Basin,
AZT, over to Belota Ranch Rd, Italian Trap, Chiva Falls, down Reddington.
What's your required singletrack quotient? Because I can think of a LOT of dirt centuries but no continuous 100-mile stretches. Some are close! There are stretches of the AZ Trail that run way-long. You could probably also assemble a cloverleaf of singletrack through Flagstaff and accumulate 100 miles.
One dirt century that's been tickling the back of my brain the past few years is a circumnavigation of the Chiricahuas. I believe the combination of roads is like 104 miles or something...but it's all dirt road. I'd probably set up a geared 'cross bike for it, honestly, since there's at least one bit where you'd have to hump up about 2200' to get over a ridge.
I'm intrigued by your Chiricahuas idea, Paul. I've got a complete plan of a (mostly)dirt road tour that goes from Tucson to Las Cruces, NM (where I grew up) that includes Greaterville Canyon, the Dragoons, ranch roads, and a trip up to Onion Saddle in the Chiricahuas, but haven't executed it yet, mostly because I'm worried about drug activity in the space between Antelope Wells and Santa Teresa.
Skidmark posted up a S. Arizona dirtroad tour a few years back that he did on a fixed CX. EDIT: here's the link... I really want to do this ride.
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