I am with Feitsbob here. between the fit questions and the shifting sounds like you need in person advice from a profesional. did you buy it from a shop? used or over the counter at Wallymart?
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk