Located near Farmersville, Sister Grove Park features eight miles of really run singletrack. It consists of four loops, Puppy, Safari, Lake, and Sister. All of the loop run clockwise.
Be sure to look out for wildlife, hikers, and photographers. There are restrooms available, though they are closed during the winter months of November through March. Water is also available but is turned off from November through March.
You can see a map of the four loops here: https://www.onepixelborder.com/sistergrovemap.jpg.