With many climbs, this section of the Arizona Trail is excellent singletrack threading its way into hills and valleys. The trail is generally wide but not too wide, with a good tread of dirt or gravel. It is almost entirely rideable, with only a few hikes required in the steepest sections.
This is big and remote country so take plenty to drink, eat, and repair with. Thorns are thick in the lowlands, so skin protection and a tubeless system are highly recommended. At a minimum, tubes should have Slime in them.
Other access notes: The Florence-Kelvin highway is mostly gravel so it is typically faster to go around via 79, 60 and 177. Note that Price Road does not connect from Florence to Kelvin except by extreme 4X4 trails. Nearest services are in Superior and Winkelman.
Kelvin Trailhead access: Turn off 177 and go south through Kelvin on the "Old Florence-Kelvin Highway" for 1.5 miles. Just before the railroad crossing and Gila River bridge, turn right and drive west for 0.5 miles to the trailhead. In addition to a spacious parking area, there is space for informal camping on this public land.
Go through the gate and ride down the road. After 0.3 mi, turn right onto fine singletrack. This is where your ride begins. You'll climb gradually to the top of the ridge for about 2 miles. This is high point of the section, and the rest will be a thrilling descent. Descending the tight west switchbacks you'll soon glimpse the old iron Southern Pacific railroad bridge ahead, and you'll continue to lose elevation until you reach the bridge.
Back at river level, the trail meanders west but soon climbs again into the hills. Contouring around The Spine, the trail drops back to river level. At 9.5 miles pass through a metal bar fence. Now comes 1.3 miles of road, but don't worry you'll soon be back on singletrack.
Just past Walnut Canyon go through a metal gate and resume riding on singletrack. Once again the trail leaves river level and meanders up into the foothills with tight turns and rideable grades.
Eventually you'll slip through a narrow gap (or yard sale in the cliffs) and descend to intersect with a 4X4 road. Follow this road uphill for 0.3 mile to the Red Mountain trailhead and AZT - Picketpost TH to Red Mountain
segment. In the other direction, the Gila River can be accessed and water is drinkable once filtered, assuming the river is flowing.
Red Mountain access is a serious 4X4 adventure in itself: 12 miles into a very remote area with some deep ruts and small bedrock ledges. You'll need to be completely prepared for backcountry 4X4 if you intend to ride this route, including fix-a-flat and tire changing capability.