USGA Proposes MOI Limitation on Drivers

[John Kirk]

USGA proposes limited MOI in drivers
By E. Michael Johnson
Golf World

The USGA sent a memo, obtained by Golf World, to manufacturers on Thursday, announcing a proposal to limit moment of inertia in drivers. If adopted, the proposal -- which covers driving clubs only -- will go into effect March 1, 2006.

In simplest terms, MOI relates to a clubhead's resistance to twisting on off-center hits. A club with a high moment of inertia can be said to be more forgiving of hits away from the center of the face. In a March 30 notice to manufacturers, the USGA noted that the moment of inertia in driver heads had approximately tripled since 1990. That notice said that going forward the USGA would be looking at three areas of equipment: spin generation, moment of inertia and the adjustability of woods and irons.

What this means for you

• MOI is all about providing forgiveness. By placing a limit on moment of inertia, the USGA is placing a limit on your ability to swing from the heels without worrying about where the ball is going.

• By acting relatively soon after its March announcement, it's clear the USGA is intent on keeping driving distances where they are. Expect any future technology that would allow substantial gains in distance to be squashed.

• Manufacturers aren't just going to throw up their hands and say "We quit." Expect club companies to continue to work with creative geometries, customization and possibly expand on adjustable weights as a means to provide better equipment going forward.

Under the proposal, driving clubs would be limited to an MOI of 4,750 gm-cm squared for the MOI around the vertical axis through the clubhead center of gravity, plus a tolerance of 50.

"Research conducted by the USGA has shown that the clubhead size limitations already in place will not effectively prevent increases in clubhead MOI beyond the levels achieved by clubs which were submitted to the USGA prior to March 2005," the notice said. "The USGA has allowed substantial increases in MOI, but it now believes that a limit is appropriate."

In March the USGA said it was "concerned that any further increases in clubhead moment of inertia may reduce the challenge of the game." The primary concern is the potential development of a strong, lightweight material that would allow for 460cc drivers with an incredible amount of free weight to move around, providing a super-high MOI.

"We had thought maybe clubs had reached a natural limit on MOI with the head size of 460cc, but with further research and analysis we came to a different conclusion," said USGA senior technical director Dick Rugge.

Most large-headed drivers currently on the market are in the 4,000 to 4,300 MOI range. Yet when asked if anything had come across his desk that either exceeded or bumped up against the proposed limit, Rugge would only say that "we don't discuss individual submissions. And I don't know what exists in the labs of individual manufacturers. This is based on our own research and modeling of what could happen. And that showed that manufacturers could respect the head size limit but produce clubs with a significantly higher MOI, and we felt it better to act well prior than after the fact."

Rugge said the concern was both distance and forgiveness driven, a point made in the communiqué to manufacturers when it stated, "further increases in MOI could reduce the challenge of the game by reducing the skill required to hit the ball straight. In addition, that could also result in an increase in average driving distance by reducing the likelihood that swinging faster will produce a poor result."

Although the proposed test protocol calls for only one MOI measurement (there are four primary MOI measures), Rugge said the MOI around the vertical axis through the clubhead center of gravity is "the one we believe to be the most critical as it relates to forgiveness, and our research shows that limiting this area of MOI should be adequate. If we find otherwise through our data collecting process, we may revisit it."

And what about the manufacturers who now may have one more area for design improvement limited? "Our primary concern is to do what's good for the game of golf," Rugge said. "We want to be considerate of the needs of the manufacturing community, and take their needs into account, but we always need to think first about what is best for the game."

Representatives from several major equipment companies either could not be reached for comment or declined to comment at this time. The USGA has asked that all written comments on it proposal to be submitted by Nov. 30, 2005.

E. Michael Johnson is the equipment editor of Golf World magazine

[A_Clay_Man]

the USGA is placing a limit on your ability to swing from the heels without worrying about where the ball is going

Hey, I thought that was the architect's job?

[TEPaul]

The USGA floated this word on concern about MOI and spin rate of golf balls twice, right around the Masters. What did I say back then but that they were into the precursor to the "notice and comment" period? This I expected, but what I can't wait to see is what their reaction will be when the manufacturers get finished reacting to this proposal and when they all get into the formal "notice and comment" period. What'll go on next is the sort of mating dance of legality innuendo and power politics. Let's hope the manufacturers don't act too adverserial over this and if they do let's hope the USGA doesn't back down as they did over the "optimization testing" debacle.

[Brent Hutto]

If the USGA had shown any ability whatsoever to control ball speed, they might have some credibility with this proposal. Given the past decade of ignoring huge improvements in ball technology, this strikes me as a completely ass-backwards thing to be fiddling with. Obviously, they are going to fish around until they find a highly visible and meaningless gesture that appears to "crack down" on technology while being unobjectionable to the manufacturers. I'll leave it as an exercise to the reader to draw the parallel to whatever current political events seem appropriate.

A guy who slices his tee shots and gets maybe 210 yards on the ones he manages to keep out of the trees can use one of the new huge drivers and maybe spend a few minutes less per round searching for lost balls. It's nice to know that the USGA is going to protect the integrity of the game by eliminating that option.

Meanwhile, Vijay Singh is going to be limited to a driver pretty much equivalent to the one he's using now while continuing to use a ball he can hit 310 yards in the air. The best players are taking advantage of the shortcomings of the obsolete ball specifications and hitting it prodigous distances. They are by and large not using the very highest MOI clubheads but since they might start using them at some point in the future I guess they need to be outlawed now.

The pattern seems clear. The USGA sees no way to meaningfully roll back or even limit future increases in distance for the best players. Therefore, they are taking the old geezer attitude of "Well, if they're going to hit it that hard let's at least make sure it spins enough so they hit it crooked". I predict they are absolutely dead wrong if they think more spin will make Vijay and Tiger and Ernie and all the 20-something bombers arriving on Tour begin to hold back and swing less than flat-out to avoid curving the ball into trouble. Not going to happen.

So two things are obvious. 1) The rule makers will continue to have their head up their collective behind and will remain unable to respond directly and meaningfully to changes in equipment technology. 2) Everything I have to say on the subject is simply repeating and elaborating on the same basic point. So that's my final comment on equipment regulation. None of it affects my game the least little bit anyway so there's no reason for me to worry about it.

[Doug Siebert]

Brett,

Why are you so negative on this?  This isn't making any clubs currently on the market illegal.  Were you hoping that a 2006 driver model would let you hit the ball straight without fixing whatever in your swing is making you slice?  Do you really want technology to solve those problems for you?  You know, we'd all make more putts if the hole was 6" in diameter, but I for one don't believe that equipment and rule changes should be making the game easier for us.

I know these equipment threads usually devolve into someone asking why those of us who think the ball should be rolled back don't find some balatas on Ebay and play with them, or play our rounds with a persimmon driver or hickory shafted clubs.  But I LIKE the technology changes that have improved equipment's consistency and longevity.  I'd hate it if the rules had banned non-wood shafts, because we'd always be breaking shafts, worrying about warping, they wouldn't be matched with each other, etc.  My first driver was persimmon, but it was a pain because you gotta make sure it stays dry so it won't swell and crack, and you had to protect the face against damage, screws would come loose after a while and so on.  Balata balls performed great but damn they didn't live very long, the Professional was better but still had a limited lifespan.  The overlooked breakthrough of the Pro V1 was that it lasted essentially forever -- it'd never get so damaged it would affect the ball flight in a meaningful way unless you are a plus handicap or pro, so even if they cost more you kept them until you lost them or hit them in the water.  Without the rubber windings inside they all play the same, there isn't a "dead" ball or two in every box that doesn't go quite as far.  That's the one and IMHO only role technology really should have in the game, unfortunately things changed when Ping entered the scene and its all been about people trying to fix their slices and shanks with equipment instead of improvements to their golf swing.

[Brent Hutto]

Why are you so negative on this?  This isn't making any clubs currently on the market illegal.  Were you hoping that a 2006 driver model would let you hit the ball straight without fixing whatever in your swing is making you slice?  Do you really want technology to solve those problems for you?  You know, we'd all make more putts if the hole was 6" in diameter, but I for one don't believe that equipment and rule changes should be making the game easier for us.

My only point was that I find it annoying that they're screwing around with size or MOI of drivers while letting the golf ball velocity continue to increase. I won't be paying any attention whatsoever to any equipment pronouncement that the USGA makes until they show that they've taken some meaningful step to effectively regulate ball velocity. That's all I'm saying. Fiddling while Rome burns and all that.

[EDIT] And just to be clear, I don't use a high COR driver. My driver has 14 degrees of loft, about a 300cc head and a very flexible 44" shaft. And I don't use a ProV1x, I can't hit the ball hard enough to get any benefit from the new technology golf balls that let Tiger and Vijay carry it 310 yards in the air.

The USGA reminds me of a contractor you hire to fix a leak in the roof. They come piddle around but it still leaks. When you bring them back in to address the problem they say "Hey, look we can put a deck on the back of your house and build an extra bathroom. We can even finish the basement and turn it into a rec room" all the while letting the roof drip, drip, drip every time it rains. At some point you tell them to shut the hell up and patch the freaking roof. Now. Not study it, not say they have it under control. Fix it and show me that it doesn't leak any more.

[Kyle Harris]

Doesn't clubhead twisting have more to do with the shaft and less the clubhead?

Limiting the MOI of the clubhead would imply that the clubhead actually changes shape at impact.

I would think that limiting the MOI of the shaft would do more.

[Brent Hutto]

A shaft's diameter is so small that moment of interia is not a meaningful quantity about the axis of clubhead rotation. Shaft flexibility (longitudinal and rotational) and moment of intertia (longitudinal only) affect the movement of the clubhead relative to the butt of the club during the swing. During the very short interval of actual impact, shaft characteristics are not of a magnitude to have a measurable (or significant) effect on the reaction of the clubhead. For that fraction of a thousandth of a second the shaft could be a wet noodle or a solid steel rod and it wouldn't matter at all.

During the moment of impact, a clubhead with high moment of inertia in the heel-toe dimension will deflect less than one with a low moment of intertia. That's why 460cc clubheads with the weight pushed out to the edges are somewhat more forgiving than an old 200cc wooden clubhead with the weight more uniformly distributed in both center and edges. The MOI about an approximately horizontal axis (top to sole MOI) also has an effect on golf ball spin when combined with the loft of the club. That's one way (characteristic time being the other) in which modern oversized clubhead reduce ball backspin and enable (in combination with modern lower-spin balls) that high launch with low spin that is so effective for the strongest players.

[Craig Sweet]

Brent, with the right shaft,club head and ball you could probably gain 20 yards without swinging any harder. Is this going to make your course absolete? No...it's call making the course more fun.

[Doug Siebert]

Craig,

If hitting further is the route to "more fun" as you seem to believe, wouldn't playing up one set of tees accomplish the same goal?  Or designing shorter courses in the first place?  If that's the case, why isn't Fazio being called in to shorten courses instead of lengthen them?