you might want to check the NEMBA web site. I know they just reworked a bunch of trail out there. The route I am most familiar with starts at the campground swimming area then loops up to the fire tower, then down the other side of the hill and back to the camping area. There is a LOT more to it than that, but it is a nice ride anyway.
If you haven' ridden in the Wendell SF, try that too. REALLY nice stuff in there.