99% of the mountain biking population calls this exact route "Whiting Ranch Loop", or just "Whiting" for short.
This is a great loop through Whiting Ranch that has many branches to create your own trail suitable to your enjoyment and fitness level.
There's a mountain Lion warning for this area. Be alert. It gets pretty busy on weekends so come early. Very popular with local hikers so be prepared to share the trail.
Park in the shopping center across Portola Parkway. Cross Portola and start at Borrego Trail
. Borrego trail is a very slight gradual positive grade for approx. 2 miles. At the end of Borrego take the fork to the right up Mustard Road
is a fire road that gets steep as you get further up it. The road is about .6 miles with around 350' of climbing. At the top you'll reach 4 Corners.
Begin a singletrack section by going down Cactus Hill Trail
. At the first fork in the road, continue right down Sleepy Hollow Trail. Take the next fork right at Serrano Cow Trail
. Meet up with Live Oak Trail
or Serrano Creek Trail
and continue until you're back to Portola Pkwy. The last .75 miles, head west on Portola to get back to where you parked.