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Bowling Ball Side Weight
The United States Bowling Congress (USBC) states that a bowling ball 10.01 pounds or more may have no more than one ounce difference between the sides to the right and left of the finger holes or between the sides in front and back of the finger holes.
A DoDo scale is needed to weigh the ball for side weight after drilling. If a ball has more than one ounce of side weight after drilling, an extra weight hole must be drilled into the ball to bring the side weight measurement below one ounce tolerance measured on the scale.
A ball used without any holes or indentations may not have more than one ounce difference between any two halves of the ball. This pertains to bowlers who use one or two hands and prefer not using finger holes for gripping purposes.
A side weight imbalance after a ball is drilled with gripping holes influences bowling ball motion. In modern terminology, side weight is a compatible measurement based upon the Pin placement relative to a bowlerâ€™s Positive Axis Point (PAP) and the Center of Gravity (CG) marking on the surface of the ball.
Side weight may be thought of as a "pulling power" weight when the mass of the ball near the Pin is located near the PAP. The strong side of the ball, so to speak, is the PAP side of the ball and with positive side weight, you will achieve a level of "pulling power" as your ball enters the pocket.
With the variety of modern day core shapes and sizes in high end bowling ball equipment, the degree of side weight is trumped by the drilling layout option a bowler chooses. So long as the final weight of the ball adheres to and conforms with the USBC requirements of one ounce side to side measurement after drilling, a bowling ball is legal to use in sanctioned competition.
Many drilling options used in asymmetric core designed bowling balls create a very high Differential of RG and, therefore, a good deal of track flare potential. The Ratings of Differential and Track Flare are the most important measurements with respect to ball motion in comparison with side weight. Side weight is a by-product of core shape and bowling ball symmetry.