The Moment of Inertia (MOI) of any object is a measurement of its resistance to being put in motion around a defined axis of rotation. In essence, Moment of Inertia is a measure of a body’s resistance to angular acceleration or simply put – club twisting. MOI comes most into play on imperfect contact, when the ball and the club face meet someplace other than the sweet spot.
As it relates to a set of golf clubs, if each club in a set requires a different amount of force to swing the club (rotating the club around your body), the golfer can not be as consistent when needing a different amount of force for each club in the set. Club MOI Speedmatching as it is called, scientifically makes each club require the same amount of effort or force to swing. The required force can be measured by an MOI machine.
More weight distributed in the center of the assembled club will make it have a “low” MOI. Distributing the weight away from the center of the club towards both ends will make it have a “high” MOI. A higher MOI will be more resistant to twisting at impact. Mishits will fly straighter, and the club will be more forgiving when ball contact is made away from the center toward the toe or heel. The club will feel like it has a larger sweet spot. The same is true with the putter. A higher MOI will enable it to be more forgiving.
MOI Speedmatching and the traditional Swingweight matching for a set of irons are both based on the same principle – having the full set of irons feel the same when you swing them which has obvious benefits to the golfer. But, these two concepts are rooted in quite different approaches. Swingweight matching has been around for quite awhile and is a time tested standard in club building using a special weight scale designed for golf clubs. Swingweight is all about the weight distribution between the head of the golf club and the grip end of the golf club. Increasing the head weight and increasing shaft weight make swingweight increase, increasing the weight of the golf grip makes swingweight decrease.
MOI Speedmatching can be a replacement for Swingweight matching in the fitting process. However, MOI is a fairly recent concept in golf and not quite yet widely accepted by much of the golf public as beneficial. Those individuals who are always looking for new ways to tweak their clubs in order to achieve maximum performance know about MOI Speedmatching. The science behind it is sound. MOI – is an actual physical measurement that is made for a golf club, it has dimensional units of mass/(length*length). It is a measure of how easy or difficult it is to swing a golf club. The MOI Matching System consists of a technical diagnostic machine. The machine along with a ruler and gram weight scale are used to perform all of the measurements and calculations required to determine the MOI. Clubs with MOI Speedmatching are starting to make their way onto the professional golf tours.
During the MOI matching process, golfers are fitted for the best head, shaft, grip, and club length combination based on the same fitting procedures as a standard fitting. But, after the heads, shafts, grips, and lengths are determined – MOI Matching is used as a guide in how the clubs will be assembled. MOI will indicate adjustments for final head weight and club length. Unlike with Swingweight matching, the weight of the grip has little if any influence on the measured MOI of a golf club.
Every regular golfer knows the longest club they hit well, and therefore have the most confidence in playing. This club is defined as the one, which the golfer hits the ball solid and on-center more often than the other longer clubs in the set. This “favorite” long club is measured for its MOI using the MOI Speedmatching System. Using that discerned value as a benchmark, all of the other clubs are then built to match the MOI of that favorite long club.
This is what technically makes an MOI Speedmatched set of clubs – a better shot-making and consistent solution over Swingweight matched clubs. Swingweight matching does not make each club equal as to the amount of effort or force required by the golfer to swing each club and hit the shot as MOI Speedmatching does. But, since every golfer can be quite different in terms of their tempo, strength, and swing mechanics, the right MOI must be identified and custom fit for each golfer to allow the concept to properly work. This goes back to that “favorite” long club that a golfer finds easy and consistent to hit with accurate results.
For the vast majority of golfers, when MOI Speedmatching is performed, they will not notice a significant difference and perhaps none at all in the actual swing feel of all of the clubs in the set. What they will see, is an increase in the percentage of solid on-center hits with their clubs – and this equates into game improvement.
The MOI Formula is Simple:
Higher MOI = Less Twisting of the Head from an Off-Center Hit = More Distance from Off-Center Hits.