Matching Golf Clubs by Moment of Inertia – a Replacement for Swingweight

What is MOI Matching?

The MOI of any object is a measurement of its resistance to being placed in motion around a defined axis of rotation. Related to golf clubs, if each club in a set requires a different amount of force to swing the club (set the club in motion to rotate around our body), it stands to reason that the golfer cannot be as consistent swinging each different club in the set. In most simple form, this is what sets MOI matching apart from matching clubs to the same swingweight. Swingweight matching does not make each club the same in terms of the amount of force required by the golfer to swing each club and hit the shot. MOI matching does. However, because golfers can be quite different in their strength, tempo and swing mechanics, the right MOI must be identified and fit for each golfer to allow the concept to properly work.

Is MOI Matching a new high-tech clubmaking concept?
Not at all. Actually, we believe from our research that back in the 1920s when swingweight was developed, its originators were aware of the principles of MOI matching and tried to make swingweight matching of clubs the same as MOI Matching. They failed because the principle of the swingweight scale they developed could not truly accomplish the task of measuring the MOI of a golf club. Over the decades since the development of swingweight, engineers familiar with the principles of MOI have always been in agreement that MOI matching would truly make all clubs within a set swing with exactly the same feel, while swingweight matching could not.
Does MOI Matching change the fitting process for the golfer?

No. MOI Matching is simply a replacement for swingweight matching in the fitting process. Clubmakers will fit golfers for the best clubhead, shaft, grip and length based on the same fitting procedures that they have developed and with which they are confident. Once the heads, shafts, grips and the lengths are determined by the clubmaker, then MOI Matching is brought in to guide the clubmaker in how the clubs will be assembled with regard to final headweight, and in some cases, final length adjustments.
Is there any aspect of the fitting or performance of the shafts that is changed by MOI Matching?

Very rarely, if ever. As we said, the selection of the shaft is made on the basis of the same fitting procedures the clubmaker is comfortable with using to identify the best shaft for the golfer’s strength, swing speed and swing characteristics of downswing transition, downswing tempo/acceleration and wrist-cock release.

However, it is very likely that because of the final head weighting requirements of the MOI Match for each club, the frequency progression of the shafts will be different than if the clubs were swingweight matched. Normally, if the progression in butt frequency was 4cpm between clubs in a swingweight matched set, the progression will change because of the different headweight changes in the MOI set, and NOT because of any change in trimming of the shafts. In all of our testing, and in the reports of actual MOI fittings that clubmakers have done, we have yet to hear of one case in which the golfer required an adjustment in the tip trimming to offset the different progression of frequency from shaft to shaft within the set that came from the MOI matching headweight requirements. In short, 99% of the time we believe the MOI matching will not affect the golfer’s perception of the shaft fitting.
What will a golfer notice when switching from swingweighted to MOI matched clubs?

No BS, we have yet to hear from a clubmaker using the MOI system who reported that a golfer for whom MOI matching was performed did not notice a difference in the swing feel of all of the clubs in the set, and a minor to significant increase in the percentage of solid, on-center hits with their clubs. If the golfer “waggles” each MOI matched club, if they are sensitive to the feel of each club, they will detect a progressively increasing headweight feel as the clubs get shorter in the set. But as soon as the clubs are swung full, the golfers all report that they can close their eyes, switch clubs in the set, and not really detect any difference in the total swing feel of the clubs from each other.
If I take a set of MOI matched clubs and then measure each club on a swingweight scale, what will I see?

Depending on the MOI each club is made to possess, the swingweight of the clubs in am MOI matched set will normally increase from the longest club in the set to the shortest. However, what the longest club’s swingweight is compared to the shortest, and what the progression in between can be quite different, again, depending on the MOI to which the clubs in the set are built, the lengths each club is fit to the golfer, and the weight and balance point of the shafts chosen for the golfer.
Will the woods and irons all be built to have the same single MOI?

No. TWGT testing and feedback from many of the clubmakers using MOI matching in their work has showed that because woods and irons are so different in their length ranges, better results were obtained by matching all the woods to one MOI, and then matching all of the irons to another MOI, with both chosen specifically for each golfer either on the basis of the “favorite club” or the “test club” approach.

What about the wedges – should they be built to have the same MOI as all of the rest of the irons?
Again, this was another aspect of MOI fitting and matching that TWGT has spent some time investigating. What we found was that any of the wedges that are chiefly used by the golfer for less than a full swing, it should not be matched to the same MOI as the rest of the irons, each which are predominantly used with a full swing. In general, because many golfers do use the PW and AW (gap wedge) for full swings more than they do the SW and LW, it is ok to make the MOI of the PW and AW the same as the rest of the numbered irons. But for the SW and LW, they are better off being built individually to an MOI or swingweight based on the principles taught in the book, Common Sense Clubfitting: The Wishon Method.
How about the putter – should it be MOI matched?

Most definitely finding the right MOI of the putter for each golfer’s feel and stroke mechanics would improve putting consistency on the greens. However, this is far easier said than done at this point in our MOI research. In the woods and irons, because there are multiples of each type of club, it is not difficult to ask a golfer to provide a present or past wood and iron that has been a “favorite club”, to which all of the other woods, and then all of the other irons would be MOI matched. But with the putter, it is not that practical to ask a golfer who is not putting all that well to bring in a “favorite putter” to act as the MOI guide – logic says if the golfer had/has a favorite putter, he/she would be using it at present and thus not need to change the MOI!

However, if the golfer DOES presently like the stroke feel of their putter but was interested in trying a different head model in a new putter, then the favorite putter should be MOI tested to provide the MOI benchmark for building or altering the new putter so that it had the same stroke feel the golfer likes.