The fire roads can get loose and dusty after the park district grades in mid summer. The trails stand up pretty well to rain but will need a few days to dry out if there are a series of storms.
This loop accesses the only easily accessible singletrack in Mt. Diablo State Park and includes some excellent climbing and fun descents. It can be ridden in either direction (although it's easier to ride counter-clockwise to avoid the short but steep sections on Wall Point Road
You can park at Monte Vista High School (during non-school hours) and have three miles of road to reach the Dan Cook singletrack or about 1 mile of road to reach the Macedo Ranch staging area is going clockwise.
This is a loop that has a bit of everything: flowy singletrack, climbing and rocky descents. Well, not everything - there is nothing flat except the paved roads. The views from Wall Point Rd are spectacular.
The loop is easily accessible from anywhere in the Danville/Alamo area but this description starts at Monte Vista High School.
Ride on pavement to get to the start of the dirt at the park entrance. Go east on Stone Valley Road, turn right on Green Valley Rd, go about a mile to Diablo Rd (traffic light), turn left onto the bike path on the north side of Diablo Rd. Watch for hikers on bike path. Note: this is a MUCH safer option than riding on the narrow, shoulder-less Diablo Rd.
Turn left into Diablo (a private community) on Calle Arroyo. Please note that the Diablo residents have asked the police to enforce their stop signs. It cost me $275 to roll through one. Follow Calle Arroyo past several holes of the golf course and the club house. Turn right just after the club house on Club House Road, then take an immediate left onto Alameda Diablo. In about .8 miles take the short path off to the right that connects to South Gate Road. Follow South Gate road for about .3 miles to the park entrance gate.
Just after the park gate, turn left onto the Summit Trail. This trail, also known as Dan Cook is a wonderfully flowy, legal, singletrack trail. It has a more difficult option available on the left about 1/4 mile in. Both options dead end into The Summit Trail fire road which goes up Dan Cook Canyon. Turn right on this fire road and head up until you reach Live Oak campground and pavement. Continue up the paved road until you reach the parking lot for Rock City. Rock City is an area that has particularly interesting rock formations - it is worth a visit.
From the Rock City parking lot, turn left and go down to South Gate Rd, turn left onto South Gate Rd and go about 100 yds, turn left onto a well marked fire road, Wall Point Rd. Continue straight on Wall Point Rd and climb another 100 ft or so. The views here, and the rest of the way down, are great.
Follow Wall Point road down for about 3.5 miles. This is also a popular route for hikers and equestrians and there are some steep rocky sections and some off camber sharp turns so, keep your speed under control. Wall Point Rd dead ends into a fire road. Turn left and go about 1/2 mile then turn left on a fire road that leads to the Macedo Ranch staging area. This ends the dirt portion of the ride.
To return to Monte Vista High School: exit the Macedo Ranch parking lot and proceed down Green Valley Road, turn right at the stop sign onto Stone Valley Rd. In about .25 miles you'll be back at Monte Vista.