Dallas Off Road Bicycling Association (D.O.R.B.A), has more than a dozen trails that we maintain in the Dallas / Mid Cities Area. Riders ride all of them on Hard Tails. Of course your skill level will be a big factor in whether you can handle them, but your frame will be just fine (the fanatics like to ride them on single speed hard tails). My personal favorites are Boulder, Oak Cliff Nature Center (aka OCNP), and Cedar Hills State Park. If you want a fast circuits trail that has a beginner to high bigger rating try River Legacy. The others that are mentioned are fast High Beginner to Intermediate with some optional Expert Sections. If you are a rock hound, try out Bar H Ranch, IDB, or Johnson Branch. I encourage you to log on to DORBA.org . Our Trails area and the Forums will give you more information and opinions than you can imagine. Feel Free to post to me for more information if you like.