Driver Tech 101

High M.O.I. Rules

Driver Tech 101You can tell by looking at the latest square and triangular clubheads that the driver market is changing before your eyes. Other new drivers look conventionally shaped on the outside, but are vastly advanced on the inside. Regardless of their shape, most of the latest models look plain huge. Ever since the United States Golf Association ruled that driver clubheads had to max out at a 460cc clubhead volume, club designers have taken the next obvious route in order to improve their products’ performance in your hands: advancing technology.

And that technology comes in a few different flavors. For starters, you may wonder why the likes of Callaway’s FT-i, Nike’s SasQuatch Sumo2 and Titleist’s 907D1 are shaped so uniquely. Well, their shapes make for a high Moment of Inertia (MOI). Sparing you the technical jargon, this means the clubhead’s dimensions and weighting make the club considerably more stable at impact. And that translates to the ball behaving as if you’ve hit it on the screws, when you don’t. So the ball still gets the most distance and best accuracy it can, even when you miss the sweet spot. The farther you miss it, the more ball speed you lose. If you made contact an inch off-center on an old driver, you’d lose roughly seven to 10 miles per hour of ball speed. Same shot on a higher MOI driver, you’ll lose only six mph, say experts.

“The new head shape allows us to put weights inside the head in places we couldn’t put it previously,” says Dr. Alan Hocknell, Callaway Golf’s Vice President, innovation and advanced design. “Those places are farther away from the center of the head than ever before. The head is more stable than ever. As such, that larger MOI creates a greater off-center ball speed and less shot curvature. Those two things combined lead to longer, straighter shots.”

Think about a figure skater making a pirouette. As she pulls in her arms, she spins faster without apparently adding any energy. That’s because she’s reducing her MOI and pulling her weight inward. To slow down, she swings her arms out wide and creates a higher MOI. That’s essentially what club manufacturers are doing within these odd geometries—stretching weight inside the clubhead as far away from the center as possible. That significantly increases the stability.

“It’s made it more enjoyable for the player who is ability-challenged,” says Hocknell. “And it’s changed the pros’ approach to driving, too. In the past, they tried to shape shots; more often these days, they’re just trying to hit long and straight shots because the equipment is set up for it.”

The rise in MOI is nothing new. In fact, as clubheads have grown significantly size-wise the past few years, MOI has risen dramatically. And that’s resulted in a tighter shot dispersion and longer drives. It’s just that companies now have figured out alternative ways to really boost MOI’s effectiveness. “A lot of driver development over the past few years has been about MOI, but it’s been presented to the consumer as an increase in head size, and bigger is better,” says Hocknell. “We’ve (actually) increased the MOI in the head every time we made it larger. So those increases in MOI have been feigned by people the last few years and have mostly manifested themselves in higher ball speeds from impacts that are not in the center of the face and from shots that have gone generally straighter than they have in the past. So the latest speak about MOI is, in most cases, an evolution. We have to be more explicit talking about MOI now, because the clubhead volume is limited, particularly in the use of more than one material to gain an advantage when you’ve only got a limited volume to play with.”


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