One of the best mountain bike rides we've ever experienced is the Flume Trail over Lake Tahoe. Count on quite a bit of climbing at altitude, so don't set out without some riding in your legs. The mostly single track is incredible and only outdone by the unbelievable Lake Tahoe views. Don't sweat it if you left the bike at home. We rented bikes from a wonderful shop at the end of the trail. Bikes are top quality. From the shop, shuttles are available to take you to the trailhead so you can leave your car at the bottom of the ride/trail and head home from there. NOTE: there's a great cafe right there too. You'll need to refuel after this ride! It's called Tunnel Creek Cafe.
If you want to drive yourself and have all your equipment, here are two routes to get there from Reno:
Option 1: Scenic Route -- Make your way to US 395 south to the Mount Rose Highway (State Route 431). Take Mt. Rose Highway all the way into Incline Village. Turn left at the junction with State Route 28. Continue through Incline Village and head south on State Route 28 about 10 miles. Turn left into the Spooner Lake day use area, if you make it to US 50 then you have gone to far.
Option 2: Direct Route -- Make your way to US 395 south all the way through Carson City, to US 50 West. Go up the hill 9 miles and just over the top of Spooner Summit is the State Route 28 junction. Turn right on to State Route 28 and head north for about 3/4 of a mile. It is the first driveway on the right.