I just started riding a new road bike (aluminum; full ultegra). It was assembled and tuned by my LBS and everything seemed to be spot on except... When I stand up and pedal hard, the front wheel seems to be moving as I can hear it rubbing on both brake pads (this moves the front brake calipers off center). The wheels are brand new American Classic 420s and are supposed to be good. I'm on the bigger end at 6'4", 210lbs., but that shouldn't matter with good wheels that are tuned properly. Any ideas about the wheel problem? How do I keep my brake calipers from moving off center? Any help would be much appreciated! Thanks!