I have a rear noise that sounds like an unbalanced tire flapping against the road. You hear a flap, flap, flap with each revolution of the wheel, which goes faster flap flap flap or click click click as you go faster. It is sort of not as noticeable at high speeds, because it is flapping so much. Sounds like a noise in revolution with the back wheels or axle. I balanced the tires, but it did not help. Any clues from anyone? This noise is really getting annoying. Thanks.