Big advantage, from the hole all the way thru...u will come out harder therefore giving u a better 60' etc...now if ya bike is still pulling with the 20 inch tires then u should be fine on ya e.t. without running out of gear, but if u are running out of gear then the smaller tire will hurt u on the big end...by u having a 10 mil 20 might be the idea, but if u wanna come out hard try the smaller ones...I run 18.5, right down the middle