The Magic Bicycle by John Bibee

John Kramar's parents died in a tornado. John had to go live with his aunt and uncle. While there, he finds an old bicycle that can do strange things. It can even fly! But his aunt and uncle don't believe him, even after he rescued a bunch of stolen bicycles with it! John Kramar finds out that there is a deeper world, with evil things in it. He has to rescue his family from the deeper world, before it's to late!