You can approach Adams Peak from either the east side or the west side. The east side approach is from US Hwy 395 and the west side approach is from Frenchman Lake. Since I used the east side approach, that is the only one I will list here at this time.
Get on US Hwy 395 between Reno and Susanville. About 40 miles south of Susanville or 2.4 miles south of the little town of Doyle there is a paved signed road on the west side of the highway named Constantia Rd. Follow this for 1.6 miles as it parallels Hwy 395 to a gravel road on your right. It has a sign for road 24N22X and it indicated Adams Peak 5 miles and Crystal Peak 8 miles. Don’t believe anything on the sign. It is the last sign you will see.
This road is ok in the summer and 2WD may be fine for the first 7.8 miles. High clearance will save your oil pan on this one. I drive a 4WD Tacoma and I wouldn’t drive this if it was wet or muddy. The dirt on the road looked like it would turn to slime in a hurry and there were ruts on most of the road where people have attempted to drive. If it is wet you won’t be able to keep from sliding down into the ruts.
Zero your odometer when you turn off Constantine Road. There is a nice campsite about .1 mile up this road. Go 1.0 mile stay left. At 1.4 miles take the right fork. At 5.4 miles pass through an old log landing. At 6.8 miles turn right up the hill. This road is not on the topo. At 7.8 miles you enter an old log landing and this is a good place to stop unless you definitely have 4WD and you don’t mind scratches down the side of your vehicle from the brush. Elevation here is about 6,850 ft.
If you are a bear for punishment, continue up the road another mile until the road peters out into a dirt bike trail. Elevation here is about 7,450 ft.
The route from the east is easy to follow. If you parked at the second log landing, you are prudent. Follow the road as it continues to climb. The road here is only about wide enough for a Quad OHV. In about a mile, the little road shrinks down to a mountain bike path and continues climbing steeply.
There aren’t any turns in the trail now as it heads directly up to a ridgeline. Adams Peak is on your left and soon you will get glimpses of the rocky summit. The trail climbs up a little unnamed knoll north of Adams Peak, so you have to leave the trail when you can see the saddle between the knoll and Adams Peak.
Now is the time for patience. Don’t just hike up the north side of Adams Peak to the summit. The brush and boulders are not fun to ascend. Continue up to the saddle and follow it around to the southwest side of the summit. The brush is not as thick here and it is easier to climb the last 130 feet to the summit. Pick your least brushy route and go to the top. Total hike from the log landing is about 2.2 miles round trip with about 1,350 ft of elevation gain. Plan on 2 hours.
Nothing special needed besides the 10 essentials. There is no water on the route, so bring enough.