Like you I tried the Walmart road first! Kept snapping spokes and getting rear wheel pinch flats. (I weigh in at 350lbs) But I road that bike until I wore the sprockets out. Then after some research I settled on a Surly Karate Monkey 29er. Rigid steel frame and fork, I went with single speed free wheel on Surly solid axel hubs. And Schwable Big Apple tires. I went single speed because I thought it would make me work harder, but you can go with gears if you want. I had my bike built thru WEB CYCLERY, I picked out all the components, they built it and shipped it to me. A little expensive yes, but think of it as a car that in the future you replace components as they wear out instead of throwing away a cheap bike!