These trails are rough, ruts, fallen trees, washed out areas and sometimes deep creeks but there are trails that go on forever on both sides of the silver comet, most land between mcpherson ch rd and the tunnel on the comet is public esp. to the right of the comet, one fireroad parallels comet for several miles on the right and has some good downhills and climbs, can also be picked up on right 200yds past benches after mcpherson, there is a good creek crossing trail to the right if you go back some that comes out on mcpherson.
Take silver comet trail W from 278 in Dallas, cross mt. olivet rd, cross Mcpherson ch. rd, 2mi to gravel fireroad on R, go L at int. 1mi singletrack on R between the fireroad and RR tracks, look to right at fallen tree other fireroads go on for miles and miles.
http://www.singletracks.com/item.php?c=1&i=585