This works best as a shuttle unless you want to do the brutal climb up the Mt Wilson Toll Road. This trail is rocky, technical, somewhat loose, has some tight switchbacks and is exposed. Towards the middle it gets a bit easier but gets technical again towards the bottom.
At the top of Mt Wilson there is a big parking lot below the cafe, get dropped off here and you'll see the start of the trail nearby. Get ready to smile. Anytime you drop almost 5,000 vertical feet in less than 7 miles on your mountain bike is a good time in my book!
It will be singletrack for a bit and then you'll eventually hop onto the Mt Wilson Toll Road. Be looking on your left for a singletrack. Take it and continue having fun. You'll come to an intersection with a few trails to choose from, stay right at this intersection (do not take the trail that has a TRAIL sign as that is the wrong trail) and keep going down.
There may be a few washed out sections that you are best to walk. You'll come to a sign that says "First Water," keep going straight here. Watch your speeds as you start getting closer to the bottom as you'll start to see hikers and can get busy on a nice weekend day.
Keep heading down and you'll eventually come to a road. You'll see a trail on the right side of the trail so hop on that and then you'll be at the bottom. Now you just have to wait for your ride as you probably beat the driver down.