If you start out of the parking lot by the beach at Grousehaven Lake & pretty much follow the numbered posts, you can do about a 12-14 mile loop. There is a small section early on where you are on the road for maybe a half mile. You will also need to carry your bike across the swinging bridge near the back of the park to continue on the trail. Between markers 5-8 I believe, is the most challenging part of the trail. About a 3/4 mile climb, followed by a great descent of the same length. There's a few other hills near the beginning, & after that it's just a nice scenic ride.
"You got to get up, And climb that hill again"