I am going to buy a new mountain bike and i need help on what size of bike frame that fits for me. I am 5 foot 6 and 125 pounds. I am looking at this supercycle bike because it is going for $109.99 because it is such a great price. It comes in bike frame sizes 16 inch and 20 inch. I just would like to know if the 20 inch is too small or perfect sized. Thanks