Hi, I am looking for a bike that i can ride for fitness on mainly paved trails with some dirt/gravel patches,Im a pretty big guy. ,Im only 5'8,i weigh about 310 pounds and i really dont know what should get to fit my needs,im not going to be taking the bike off of any "sweet jumps" just riding along for a workout. i have about $160.00 to get a bike,i could spend a little more though i think but im kinda low on funds for now but its worth it. I was just hoping you all could help me find the right bike,are any at walmart good for me? i dont want to break something..TIA oh and also i usually drop back to about 290 when the warm weather hits,i just gain a good bit in the winter every year,god knows why.