I'm having trouble with something on my bike, and can't pinpoint it. It seems with every wheel rotation there's a thud, I'm feeling it up the seat tube, and not in my hands, which leads me to believe its the rear wheel, but its an aluminum frame so it could be transmitting from anywhere. The rim is in true, brakes are not catching anywhere and the wheel has no bulges anywhere due to weakness or improper tube installment, and there are only about 5-600 miles on them . Any ideas? Relatively new to biking and willing to try anything, I like messing around with my bike, i've already saved myself probably several hundred in maintenance costs at the LBS by doing it all myself, and thats in just a year of serious riding. Could this be hub related?