Its a loop, but head west out of the parking area to access the bike trail. It doesn't look like a trail, and the sign warns authorized vehicles only. The singletrack portion of the trail is a little further down the trail and doubles as a hiking trail, but the senic diversity of the trail make running into the occational hiker well worth it. You also have a great chance of seeing some wildlife. Be aware of the red blazes that mark the trail, as you will easily get lost if you are not careful. Once the shared trail ends, in order the continue the loop, one is forced onto a fire road/break. Why this is a designated bike trail I'll never know. Deep ruts and huge clods of dirt make riding impossible except on the edge of the bush. You'll inevitibly end up walking your bike through the worst of it.
The bicycle trail is approximately 9 miles long, but bicycles are also permitted on the 8 miles of horse trails. Because these are multi-use trails, be prepared to meet the occasional hiker, horseback rider, or park vehicle. You'll feel like riding some more after completing the trail and the park's paved roads are perfect for that high speed riding you were unable to accomplish on the dirt trails!