Originally posted by ZetecRacing:then WHY does a lighter fly wheel on a MTX do that???? it's the same diameter just lighter and it caused gains in the quarter. same princapal as the UDP just on the other end of the crank. the reduction in diameter desn't cause it to free up as much as the lighter weight does.
Because that's like a ten pound difference instead of a one pound difference. A stock crank pulley weighs 3.4 pounds (your UDP does not save six pounds) and has a radius of about 2.5 inches. A stock tranny flywheel weighs over 20 lbs and has more than twice the radius, and probably has more of its mass concentrated at the outer edge. That means that it has something like fifteen times the moment of inertia that the pulley has.
