“Highly rideable but more technical than adjacent sections.
— John Geronimo
This ride utilizes AZT - Passage 15 - Tortilla Mountains but focuses on the north end, which is mostly singletrack through rugged terrain. South of Ripsey gate is a lot of dirt road without as much terrain.
Much of this section is rideable, but compared to adjacent sections there are more loose stones, steep, tight, switchbacks, and steep cross slopes. There is zero water--not even the option of filtering Gila River water. Combined with the serious elevation gain, it earns a black diamond. Be sure to carry lots of liquid, calories, and repair equipment.
From the "Kelvin Trail Access" north of the Gila River, ride back the way you drove in. Cross the railroad tracks and Gila River bridge, then hang an immediate right onto the singletrack trail. The trail is well-marked and quickly starts ascending away from the river on switchbacks supported by stone walls. This is a short but pleasantly challenging section with hard climbs and tight turns.
After 2.5 miles you'll cross the "Old Florence-Kelvin Highway" to what is known as the "Kelvin Trailhead (Pinal County)". This trailhead is much larger and equestrian-oriented than the "Kelvin Trail Access" north of the Gila, which is somewhat surprising because after a couple of miles this section becomes much more technical than going out to Red Mountain.
The trail gradually climbs across a series of rolling arroyo hills. Then a serious series of very tight switchbacks zig-zags up what the AZT calls The Big Hill. Next is a kind of rolling highlands that flows between peaks and eventually reaches a high point. The other side is another impressive series of switchbacks down.
Eventually you'll join an arroyo and ride carefully down a narrow spine into a sedimentary lowlands. Go through a gate at (and then follow) the dry wash downstream. After 0.2 miles, start looking left for trail markers and exit the dry wash.
This lowlands is all clay and gravel, but the trail does a good job of staying out of the really loose stuff. After many short arroyo crossings, you'll reach a gullied road with a black pipe following it. Go along this for 0.3 miles and then you are back on singletrack.
The trail climbs again and reaches a gate. Beyond this is a long section of dirt roads. (If you need a bailout option, go west 2.5 miles to the Florence-Kelvin highway and return that way.)