It can be any number of things. The wheel could be out of balance. Even if you had it balanced, sometimes those stick-on weights can fall off. There could be a problem with the tire... for example the tread can be cupped which in turn causes shake. And it is not unheard of for the tire to be less than perfect right from the factory. What else... oh yeah, wheel alignment. Yup, if that back wheel gets out of alignment (from doing chain adjustment) the front can in turn... shake. Strange but true... we were just talking about that at the recent Nelson RAT Raid.
