Leave a car at Thunder Rock. Day use parking is free there.
Ride up the trail that follows the river to the WW center. This part is gravel RR bed type path.
From the WW center, go up the Bear Paw Loop. At the T in Bear Paw go Left. This will save a bit of climbing. Bear Paw will turn into a fire road which is Chestnut Loop, keep climbing up this. Do not take the first right onto Chestnut, stay straight. Pass Riverview loop on your left. Then Pass Quartz Spurr on the Right. At the second left for Riverview loop, take a left. Doing this will maximize the downhill on Riverside Loop. When you pop back out on Chestnut, take a left and take a right onto Quartz spur, follow this to the top of the mountain and take a left onto Quartz loop. Shortly, take a right onto Chestnut, this will be a gated fire road that heads downhill. Follow Chestnut to Thunder Rock Express, take a Left. TR express will dump you out onto a the forest service road a few hundred yards from Thunder Rock Campground.

This is a nice 12ish mile loop, and is the best ride I have found there. When I lived in the south, we would pair this with boating the ocoee several times a month. The DH on Riverview and TR express are really fun and fast, and the climbing isn't too bad anywhere. Everything is rideable by a good rider, but you should find some challenge.

Enjoy!