What is Mass Bias?

The term Mass Bias refers to the fact that the center of mass of a bowling ball is not located directly under the pin of the ball.  having a Mass Bias causes the center of gravity (CG) mark of a ball to move away from the pin, resulting in a pin-out ball.  Therefore, all pin-out balls have a mass bias.  A pin-out ball is one in which the pin is at least one inch from the CG mark on the surface of the ball.  Technically speaking, the term mass bias is actually short for enhanced mass bias."  Enhanced mass bias refers to increasing the dynamic effect of shifting the center of mass away from the pin by having a specific part of the core present on one side of the ball that is not present on the other side of the ball.  Enhancing the mass bias affects the direction and rate at which the ball migrates toward its preferred spin axis.   Track flare is caused by the migration of the bowler's positive axis point (PAP) toward the ball's preferred spin axis. Knowing the location of the mass bias greatly increases the ball driller's ability to create the desired ball reaction for every bowler by accurately marking the correct layout for each ball chosen.

Introducing the deTerminator!

The deTerminator is designed to accurately find the location of the mass bias on the surface of a bowling ball and to measure the responsiveness of the ball's design to lane friction.  The mass bias location can then be used along with the pin to accurately and reliably lay out a bowling ball to obtain the most appropriate reaction for a bowler.   The deTerminator is the ONLY tool available to accurately find the mass bias of a plugged ball.

The strength of a ball's mass bias is measured by finding how long it takes the ball to reach its preferred spin axis from its most dynamic layout position.  The faster the ball reaches its preferred spin axis, the stronger its mass bias is, and the stronger the mass bias is, the more dynamic the ball is.  The deTerminator, when used properly, will allow the ball driller to produce the best ball motion for every bowler.

The location of the mass bias on an undrilled ball is found by spinning the ball two times with the deTerminator from two different starting positions, and then marking the ball's preferred spin axis on each spin.  Using these two marks and the pin, the mass bias can be quickly and accurately located.

The deTerminator will find the mass bias for almost all pin-out balls.  On some balls with weaker core designs, the mass bias cannot be found because the ball will not stabilize on a preferred spin axis.  A pin-in ball does not have a mass bias, unless otherwise indicated by the manufacturer.