I am new at biking. I have been using my old crappy Wal-Mart bike to bike to the gym its 2 miles away. But my step-dad is going to move down here and he is also getting into biking. So I want to get a good Bike so we can go 20-25 miles. But I have no clue what to buy I am 5'8 and weigh 160 pounds. How big should the bike be that I get? What kind is a good one?