The Backbone Trail will stretch from Will Rogers State Park all the way to Point Mugu State Park when it is completed. Unfortunately, large portions of this trail will not be open to mountain bikes. The first 10.65 miles of this trail, starting at Will Rogers State Park, is open to mountain bikes. This describes this route as an out-and-back route starting at the Trippett Ranch TH in Topanga State Park. If you choose to start at Will Rogers SP, do the math to come up with your own mileages to each intersection. Of course you can also do a shuttle if you want to go to the effort.
The first few miles of this route will bring you up to some ridges with stunning views of the Pacific and inland valleys. If you only have time and energy for a short ride, go up to Eagle Rock. Do a quick lollipop loop and return to your car.
From the Trippett Ranch parking lot follow the multi-purpose trail up the hill.
@ mile .13 turn left
@ mile .27 turn left again and follow the Eagle Springs Fire Road
@ mile 1.52 turn left on the singletrack up Eagle Rock Trail
@ mile 1.95 reach Eagle Rock summit. Continue straight along Temascal Ridge
@ mile 3.03 you reach the "Hub Jctn" ... continue straight on Temascal Ridge fire road. (Turn right here to follow the fire road if you are doing the Eagle Rock lollipop.)
@ mile 3.68 take the (sweet & smooth) singletrack to your left. This is signed ("Backbone Trail to Will Rogers"). It isn't sweet and smooth the whole way, but it is a fun singletrack. If it's overgrown so you can't see the trail very well, just think of it as an adventure. It will open up soon enough. You'll be glad you did.
@ mile 9.77 you reach the boundary between Topanga State Park and Will Rogers State Park. You also reach the end of the singletrack.
Turn left on the "Inspiration Point" double-track (or turn around here).
@ mile 10.64 you reach asphalt and the horse stables in Will Rogers State Park. Turn around and retrace your route.