i have a cannondale f5, have about 60 trail miles on bike in a little over a month. on last ride, a hum developed from the front wheel and the sound tends to resonate in the frame. took it to LBS i bought it from(hour away), and of course the sound goes away, but when i got home, its back. when i lift the bike off of the ground with tire barely spinning, its there, or trail riding, its there. seems more pronounced when wheel turned. any ideas?