They are crap! If you're headed off-road at all, plan on spending at least $250-300, and ideally $500-1500 for a bike that will hold up and continue to function well in the long term. Go to a real bike shop and get fitted for the bike that best fits your body and your needs. A first tune up should be included and that's your opportunity to see how your bike works and what maintenance it'll need in the future. Also plan on good quality padded bike shorts, water bottle and cage, and a basic set pack, multi tool, air pump, and patch kit so you're semi self sufficient. I know it sounds like a ton of $ and a big hassle, but a quality bike will run well for way longer than the month you can expect from a WalMart/K-Mart bike. Truly.