I am with HillRider's first post SAVE YOUR MONEY. any part you replace on the drivetrain my have unwanted consequences.
just ride the bike like it is and save up for a cool Bianchi in the spring. also I am not sure how fast you think you should be able to go ona bike, but even on a Pro level bike and in peak fitness an average of 22mph is really good and hard to sustain for a solo rider.
is there hill in Queens high enough to get a bie going 30?
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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