Croft State Park has some of the best Mountain Biking in SC. There is a little more than 16 miles of trail riding with all levels of difficulty.
Croft State Park, called Tour de' Dump by locals, is a 7,000 acre state park containing a lake, a river, horse back riding, recreational fields, etc. but it is more commonly known for its mountain biking. Made up of a little more than 16 miles of trails you can enter the Southside Loop Trail from a conveniently located parking lot. The loop itself is about 9.7 miles in length with lots of trails cutting through the the center. The trails have all levels of difficulty from flat to steep hills, and from smooth to very technical.
Address for Southside Loop Trail Access: 581 State Rd S-42-500 Spartanburg, SC 29302