Chantry Flats is a very popular trailhead for hikers-much more so than bikers. It's open to bikes, though, but you might want to plan your trip when there aren't many people out and about.
The Upper Winter Creek and Lower Winter Creek singletrack trails are where the real riding is at. Some sections are super tech and probably will force you to dismount, but for the most part it is awesome benchcut singletrack! I definitely went the wrong way around the singletrack loop: try going clockwise (Upper Winter Creek first). This will require a steep (but short) paved climb at the end after you finish Lower Winter Creek, but you'll do most of the descending on singletrack this way.
The nearby gravel road is a great spin up above the clouds! It heads up past the beginning of the Upper Winter Creek trail, past the helipad, and up to some radio towers. The grade of the road climbs constantly, but it is a reasonable angle allowing you to sit back and enjoy the climb!
There's a singletrack shortcut from the upper portion of the road that drops straight down to the helipad, but it is severely washed out and overgrown!
210 freeway exit Santa Anita follow Santa Anita all the way to the Picnic Area you will find the <br /><br />trailhead from there
http://www.singletracks.com/item.php?c=1&i=2771