Beginners: (Lake Loop 1.1 mi) Intermediate: Gold Mine Loop (6.3 mi), Cool Springs (7 mi) Advanced: East West Loop (14 mi) There are loops for various types of riders, but I have found none of them to be particularly mountain bike friendly. Most of the trails start off downhill and you have to pay for a 1000 feet elevation change at the end. There are nice scenic views of the North Georgia mountains and even creeks and springs. Deer are common and if you're lucky, you won't run into any of the bears. The eleven downhill switchbacks on the Cool Springs Loop are the most exciting thing I've run into on these trails. I know there has got to be better trails around the Chatsworth area though. Overall, the mountain bike trails seemed like good intentions on behalf of the forestry division but the trails are in desperate need of singletrack.
"I-75N to Exit 126-Hwy 411. Take Hwy 411 North to Chatsworth (right at the exit ramp). Follow this road for about 38 miles until Junction 52. Take a right at the stoplight heading east on Hwy 52 for 7-8 miles. Fort Mountain State Park entrance will be on the left. Stop at the park office for a map and permit ($2/rider)
http://www.singletracks.com/item.php?c=1&i=574