Why MOI Matching Is Important to Your Golf Game
By now, most golfers who read even a little about golf equipment know that the acronym “ MOI “ stands for Moment of Inertia. And most golfers who are aware of the MOI of a golf club have been told this is a scientific property that is a big part of how forgiving a clubhead can be when a shot is hit off the center of the face.
All that is true. The MOI that almost every golf article has referred to is the resistance of the clubhead to twisting when the shot is hit off-center. Put more of the head’s weight all around the perimeter of the head and you increase the MOI, which in turn means when you hit the ball off-center, you lose a little less distance than if you do the same thing with a head that has a lower MOI.
But there is more than one MOI when we talk about golf clubs. One of the most interesting that so few golfers know about is the MOI of the whole golf club, the fully assembled clubhead, shaft and grip all together.
Any object that is put in motion to rotate about some defined axis of rotation has an MOI. In the case of your golf clubs, during the swing we rotate the club about TWO different axes of rotation. One is our spine. As we swing, we turn back and turn through so we are rotating each club about the axis of our spine.
The other is our wrists. When we unhinge our wrist-cock angle during the downswing, we are putting the club in motion to rotate about an axis that is our wrist-cock release. So in addition to the MOI of the head itself, every fully assembled golf club also has an MOI.
Why is this important?
It has been said for years by golf club experts that if we somehow can make all the clubs have the same exact swing FEEL, we should be able to make our swing be more repetitive, and from this, be able to hit the ball more consistently on center with control. Up until a few years ago, the way golf companies would try to make golf clubs have the same swing feel was through swingweight matching. Since 1920, golf companies have built sets of golf clubs so they all had the same swingweight.
But there is a different way to make your clubs all so they all require the same exact effort to swing to gain better shot consistency. It’s called “MOI Matching” and it is gradually convincing more and more golfers that it is superior to swingweight matching when it comes to making ALL the clubs in the set swing with the same exact feel.
Our research into MOI matching as a replacement for swingweight began in the mid 90s. In 2003, Wishon Golf pioneered the very first hardware and software to allow custom clubmakers to truly build sets of clubs in which the clubs are matched to each other by their MOI. Since then, more than 500 clubmakers have invested in the MOI matching equipment to be able to fit and build MOI matched sets of clubs.
Is MOI matching better than swingweight matching? The thousands of golfers who now play with MOI matched clubs believe so. Or at least that is the feedback we hear from the clubmakers who do this. MOI is a true scientific measurement of just how much effort it takes to swing a club. Swingweight is not. Swingweight is an arbitrary measurement of the ratio of weight in the head to the weight in the rest of the club. But as club lengths change, even when you make each club have the same swingweight, they do NOT require the same effort from the golfer to swing the clubs.
If MOI matching is so good, why do all the golf companies still build their clubs to matched swingweights? Mainly for two reasons, 1) MOI matching takes more time to do and costs more money in labor to do. 2) MOI matching works best when it is customized to each golfer’s different combination of size, strength, athletic ability and swing characteristics. The big companies build their clubs to one series of standard specs so their clubs can be bought off the rack. To really take advantage of what MOI matching can offer to shot consistency, the big companies would have to build their sets one at a time, for one golfer at a time. And that is something they do not do and cannot do.
If you’re interested in MOI matching, here is a link to more information, including answers to more questions about MOI matching – https://wishongolf.com/clubmakers/matching-golf-clubs-by-moi/
Hi Tom,
If I’m not mistaken, a 3/8″ length increment between the length of each iron in a set with the standard 7 gram weight difference in each iron head will give approximately an MOI matched iron set, correct?
The question I have is if one wanted to construct a 1/4″ length increment set what would the headweight difference between each iron need to be to give an approximately MOI matched iron set, all else equal?
All the best,
Nathan
Nathan There is one other requirement in addition to using 3/8″ increments of length between the irons for a “close enough” version of MOI matching in a set of irons. The clubs also need to increase in swingweight from long to short by 0.5 swingwight points per increment. So if the set starts with a 38.5″ #4 iron at D0, the 5 iron would be 38 1/8″ at D0.5, the 6 iron would be 37 3/4″ at D1 and so on down through the wedges. I can’t remember the math right off the top of my head for that since… Read more »
It is hard not to notice the missing long irons in contemporary sets and I do find it a bit sad. There is clearly a traditionalist aspect to my golf psyche. The lofts on my 14 year old irons are 2-4 degrees stronger than what I would call the traditional lofts. But my lofts are 2-4 degrees weaker than what I have seen in contemporary OEM irons. A few weeks ago, I attended an OEM demo day (my first ever) and hit a few of their new irons. These irons were the same length as mine, but with stronger lofts,… Read more »
OWEN Let me with my 32 yrs of clubhead design experience be sure to emphasize how happy I am that low number irons are dying and going the way of the dinosaurs. From a pure scientific point of view in clubhead design, if you want to create a clubhead that has far more downside than upside to its performance, you would make an iron with a loft of less than 25*. By the very nature of its thinner body, irons are a horrible design for golfers of less skill to try to hit consistently well. The ONLY thing that ends… Read more »
For the moment, I’m beginning to empathise with the way left-handers must feel. Prior to my current 14yo set, I was still playing with a persimmon 1w and 3w and a set of 11 irons with traditional lofts, all of late 80s vintage: 1-9,PW,SW. The 1 and 2 irons were mismatching cavity backs and the rest were matching blades. I don’t own any of them anymore. As a teenager, I spent over a year playing without my woods and it really strengthened my long iron game.
Ho hum … I guess I’ll eventually jump on the hybrid bandwagon.
OWEN Back in the late 90s when hybrids first began to come into the industry, they were of course touted to be low loft iron replacement clubs – better to hit than a low loft iron because the hybrid head body had both a lower and a more rear located center of gravity to help get the ball up easier than an iron of the same loft. That part was and still is definitely true. But what disappointed me was all the big companies made their hybrids to be at least an inch to 2+ inches longer in length than… Read more »
Yes, that makes perfect sense. I would only consider playing a hybrid with the same length/loft as the long iron it is intended to replace. I suppose the hybrids with additional length are one of the main reasons why a certain percentage of golfers complain that hybrids offer less control than the long irons they are intended to replace? It seems to be a similar situation as with the common action of making graphite shafts longer than steel shafts for the same club, supposedly to achieve the same SW. I’m not sure I agree with that approach. Club length is… Read more »
OWEN You are absolutely right in your 2nd paragraph. The big golf companies are so greedy and have been for the past 30 yrs. They know that above all other things in golf clubs, more distance sells more clubs than any other factor. This is why they began to lower lofts on irons starting in the 80s, it is why they began to increase the length of drivers and woods since the 80s, and it is why they began the reign of hybrids by making them longer than the irons they were intended to replace. In short, I really cannot… Read more »
A follow up post, to the confusing musings I made previously … For the last several months, I’ve been teaching myself how to build golf clubs (thank you internet)and have now built a full and beautiful set from components (thank you again, internet). Actually, I’ve now re-built them three times! I wanted to experiment with MOI matching. Ultimately, I have concluded that there is a lot of merit in matching one’s irons to a single MOI value about an axis at the very end of the grip cap (the butt of the club). Let’s call the value MOIb, or, as… Read more »
Aarrgh. (Yet another) correction: I made a silly mistake in my calculations for MOIn, but only for WCAs greater than zero. For a set that is SW matched (or MOIm matched), from the time the wrists begin to release, through to impact, the pattern of MOIn varies from increasing with club length (like MOIw), to decreasing with club length. But certainly, by the time the WCA reduces below 90 degrees, there is a clear decrease in MOIn with club length. Closer to impact and a zero WCA, the decrease becomes more significant. So, this doesn’t really change my thinking that… Read more »
Owen Rather than respond to all the many posts you have made in your discussion, I will center my responses to this one comment you made as your last one in your discussion thread. What I was looking for back in the late 90s when I went to work on this project was to come up with a better way than swingweight to be able to match the weight FEEL of golf clubs within a set. Swingweight has always been known to be a completely arbitrary form of club weight feel matching. At that time in my research work, I… Read more »
Thanks for your response Tom. It is much appreciated. I will try matching both the MOIm and MOIw in my 4i and 9i (by adding an extra 7 grams to my 9i head for the MOIw match) and see which I prefer. I kinda sorta already know that MOIm matching will be okay for me (even if it isn’t quite the optimum), as (for similar shafts and grips) it yields similar results to 14″ SW matching, with which I am familiar and with which I have played some very good (and very bad) golf over 30 years. (I am now… Read more »
OWEN It’s a pleasure to hear from you about this because it is so easy to tell you know what you’re talking about in your experimentation with forms of matching club feel during the swing. As such, I wish you all the fun and success in your continued experimentation with the final comment that there is no question that IF you are looking for the ultimate perfect solution to matching every element of swing feel of clubs during the swing, then that is achieved with a single length assembly. The only things you have to work with to make that… Read more »
Yes, I agree that a single length/weight set is the only way to *perfectly* match for heft/feel. I said as much in one of my earlier comments which you opted not to publish — which is fair enough, I got a bit wordy there. (To anyone else who might be reading this thread, WCA stands for Wrist C0ck Angle, with zero degrees being defined as a fully released wrist, near impact.) The notion of a single length/weight set is certainly interesting. The only thing that turns me off the notion at this time, is that it doesn’t appear to suit… Read more »
OWEN The golf industry has effectively killed the 2 iron since no sets offer one anymore. The 3 iron is terminal and the 4 iron is about to be. All because of the ongoing, steady decrease in loft of irons over the past 30 yrs. You may not have followed this but 30 yrs ago the standard loft for a 5 iron was 32*. today it is more like 25-26*. All done in a “fool the golfer” process to simply sell more clubs on the basis of hitting the same number farther. Most golfers only know their clubs by the… Read more »
Hi Tom, Enjoyed reading this (old) topic … I’ve been investigating the swingweight (SW) and MOI of my set of clubs recently. As I suspected (after 14 years of ownership) I discovered they weren’t terribly well matched for SW, with a few sudden jumps of ~2 SW points between adjacent irons. The spread was such that it was impossible to match the MOI (about the wrists) of the irons without: making the short irons (which I generally like the feel of) much heavier, or losing weight from the heads of the long irons (too hard), or messing with the shaft… Read more »
Tom – I have a weird question for you. At this weekends range session, I was absolutely flushing my Tour Striker 8 iron training club. High draw that went far. However, I was not able to get any type of decent ball flight out of my irons. I am recovering from a back injury this past winter, so I have changed my swing a little. Now, I have not been fit for my irons, but I have played them well in the past. That was before my back injury. Please tell me if this makes any sense or not: Since… Read more »
BOB
Yes, that would be a valid experiment to try to see if the MOI of the Tour Striker could indicate the best weight feel and length fit for repeatibility improvement. But in all such experiments it is best to start with ONE iron to be built with its MOI the same as this training club, then go from there.
TOM
Tom,
This is all good to know. Thanks.
So with regard to taper tipped shafts, if I don’t tip and ream, is it even worth MOI matching the set in every other aspect?
Jim
JIM If you get the right MOI for the golfer to best match to his downswing transition force, downswing acceleration, strength and his sense of preferred weight feel, then to MOI match the clubs really can make a difference in terms of overall consistency with each club in the set. the shaft is a separate entity to MOI matching in that its weight has to be matched to the same golfer characteristics as the MOI< and the flex/bend profile has to be matched to the golfer's clubhead speed + transition force + downswing acceleration + the point of wrist c… Read more »
Tom, Thanks for the reply. Just two follow up questions. First, what should be done in the case of using taper tipped shafts? Second, when working with parallel tipped shafts, there is a note (#2) at the end of section 2.3 (MOI Matching by Length) of the Auditor Speed Match manual which states: ‘For the sake of consistency, the shaft should always be tip trimmed as directed by the manufacturer to achieve the desired flex characteristics and then butt trimmed to length to achieve the MOI match. If the MOI matching by length prove to be unworkable after the clubs… Read more »
JIM Taper tip iron shafts do present quite a bit of a challenge to do a set in which the clubs are MOI matched and the shafts are freq matched within the MOI match. A REAL PAIN IN THE BACK SIDE ! If you tip them, then you have to ream the hosel. If you tip them a little more, you have to ream the hosel a little more. There is no good way to do this that does not end up causing you to spend 3 times as much time to build the set. Forget that comment in the… Read more »
Hi Tom, In a PowerPoint you posted on this topic, you say to “Add additional 1/8” tip trim to achieve frequency slope seen at ½” length increment set” which I assume is to compensate somehow for building a set at 3/8” intervals rather than ½”. Now intuitively speaking, making and adjustment to the tip trim seems to make sense. But intuition aside, what is your basis for this recommendation? And how did you arrived at 1/8” precisely? Additionally, are you simply recommending just trimming an extra 1/8” off what is specified by the shaft’s trim guidelines for each iron? If… Read more »
JIM The additional tip trim is done to offset the frequency softening effect of not only the 3/8″ increments but the progressive increase in headweight to achieve the MOI match. In truth, for many shafts it may take a little more than an additional 1/8″ tip trim because all shafts do not progress in stiffness effect up from the tip in the same manner. Really, if you want to achieve BOTH an MOI match and frequency match of the clubs, you have to painstakingly tip trim, check, tip trim, check for each shaft for each club in the building process… Read more »