But these trails are subject to wear when wet. Your bike will pick up a heavy clay mud in the process. Before you go, check with this site to assess riding conditions: http://www.mtbnj.com/forum/threads/6-mile-run-conditions.23594/page-384
When you emerge at the far side of Six Mile Run you can take the Delaware and Raritan Canal towpath either to the right, back to New Brunswick, or left, on to Princeton or Trenton.
One note of caution, Six Mile Run is ground zero for poison ivy. It is along trails in both forest and fields. Wear clothing to cover your skin and be careful touching anything that came into contact with it. Or you might be "swimming in an ocean of calamine lotion."