I'm thinking about picking up mtn biking. I have a bike my dad bought me a few years ago that I never really used... and I never really grew out of it. It's a Trek Mtn Track 240, 24". I'm 20 yrs old, 5', 105 lbs. Do you guys think it will work for me? I'd be on beginner to intermediate trails (in a while). Or do I need to look for an adult model? Thanks! M.