MOI stands for moment of inertia. Something could be characterized as inert if it is resistant to movement and motion. The moment of inertia refers, more specifically, to the resistance of an object to movement around its axis of rotation. The higher the MOI, the more resistant an object is to movement.
How is this relevant for golfers? It is relevant because the main objective of golfing is to use various types of clubs to strike a golf ball and make it travel in a desired direction. The way a golf club reacts when it strikes that golf ball can affect the distance, trajectory and direction it takes. The MOI might not matter as much when you hit the ball square with the center of the clubface, but it can make a considerable difference if the ball is struck off-center.
Since a club with a higher MOI does a better job of resisting the natural tendency of the clubhead to twist on an off-center hit, the distance and accuracy of the ball’s path is less affected. This is especially the case for drivers, where a minor change in the direction that a ball is traveling can greatly affect a ball’s final resting point, since drivers are designed to cover the greatest distances. As a consequence, a higher MOI = greater forgiveness when a ball is mis-hit.
How can club design affect its MOI?
The way in which a clubhead is designed directly affects its MOI and its corresponding forgiveness factor. One early trend that major golf manufacturers incorporated into their drivers was to increase the size of the clubhead face. This lead to a bigger sweet spot and some distribution of weight away from the center of the clubhead which affects the center of gravity and leads to a higher MOI.
A more recent trend has been to move away from the traditional shape of a driver’s clubhead toward a square design which moves more weight toward the perimeter of the clubhead giving it a boosted MOI. Nike was the first major manufacturer to put a square driver on the market with its Sasquatch Sumo2. Calloway has followed with its new FT-I drivers that sport the same square design. Given the excitement generated over these new style drivers, you can be sure that other manufacturers will soon follow with square-headed drivers of their own.
Nike SasQuatch Sumo² Callaway FT-i Draw Driver