Swing variations and their resulting shaft twisting causes hooks and slices. A technically perfect swing is something that rarely happens. The great majority of swings by golfers have an inherent 5-degree variation in either swing path or club head position. In layman’s terms, this means that the club head is either 5 degrees open or closed on impact, or the swing path is either 5 degrees inside out or outside in, or the combination of both. The constant in a golf swing is variation itself. However, it is rather ironic that most golf companies publish performance statistics based upon center-hit data, when in fact, a perfect center-hit is a phenomenon that rarely occurs.
Understanding the role of variations in a golf swing, allows us to address the issue of its impact on shaft twisting. The physics behind shaft
twisting is what engineers have called the “Circular Moment of Inertia”. In other words, the bigger the club head, the more the shaft twists. From the perspective of the ball impact point, the further away from dead center the ball impacts, the more the shaft twists.
The common solution to the issue of swing variations is a bigger club head with a larger sweet spot. The 280cc size driver heads dominated the market in 2000. Larger 360cc driver heads became the industry standard around 2002. The largest 460cc heads (cc means cubic centimeters) were introduced in 2004 and because of the increase in club head size, the USGA created a stipulation for the size of the club head. The legal maximum volume displacement of any clubhead remains 460cc today. The shafts in the early days of 460cc driver heads twisted excessively. The amount of shaft twisting was further exaggerated with the bigger head. But, the shafts being designed and engineered now have reduced that twisting to a minimum. Shaft technology has improved tremendously since 2010.
The shaft is the engine of a golf club. To make a club more forgiving, golfers need shafts that twist less and the larger heads will also help. Some players like to use smaller drivers just out of habit, for the older players it may be difficult to get used the the look of the large drivers. The large 460cc drivers usually have a high MOI (Moment of Inertia), and are designed to reduce the amount of twisting on the head that an off-center hit causes and reduce hooks & slices. However, that makes it more difficult for the better players to “work” the ball or bending your shots to a draw or fade. So, some of the best players prefer using smaller heads because it allows them to work the ball better.
A 460cc driver enables you to get more club speed, therefore, hit the ball further. It also has more club face area so it is easier to hit. Lower cc drivers are old technology, and generally do not maximize a player’s performance off the drive. A larger size face makes it easier to design a variable thickness face that could offer a very high level of off center hit performance. A 400cc, 420cc, or 440cc will not have a large drop-off in benefits, but any driver head below 400cc will have a noticeable less MOI.
The large and long drivers do cause golfers to hit the center of the face less often than most of them used to when they played with smaller drivers, but everything in golf is some form of trade-off. The one advantage of a small head driver over a larger head is the ability to place more mass behind the sweet spot. A larger head has to spread the mass out just because it is so much larger. However, this advantage quickly dissipates if one is not skilled enough to hit the sweet spot.
Every driver with any size head has a single sweet spot that is about the size of a dime at best and probably closer to the size of a pinhead. There is one single spot on every driver that maximizes the delivery of the mass. As you begin to move the impact away from this spot, you lose distance. Experts state that the loss is from 7-9% on a miss of only a 1/2″, and 12-15% on a miss of 3/4”. So, regardless of size, the optimum performance will be on dead centers hits, and the size of the club head does not help you achieve this. If you will grip down on your driver an inch or two, you will most likely find your driving distance and accuracy to improve because you will hit it closer to this sweet spot more often.
So why do pro golfers use large-headed drivers? They are obviously skilled enough to come close to the sweet spot on a regular basis. I suspect that the pros know that, on average, their drives are going to be longer and straighter using the large-headed driver. While the small-headed driver might get them a bit more distance on a perfect strike, the large driver delivers better performance on slight mishits. Older small-headed drivers weighed much more (more mass) per cubic centimeter. Wood heads were solid with lead or brass weights inside and a brass or steel plate on the bottom. When steel replaced wood, the club head could be hollow (usually with a foam insert). Stronger, thinner steel allowed larger heads without increasing the weight. Titanium club faces also play a large role in driver head weight. Titanium and other exotic materials allowed club manufacturers to increase the size even more but with less overall weight. Titanium is lighter then steel for the same strength profile, but a bit softer. This has allowed club manufactures to greatly increase the size of the face of the driver and the hot spot as well as moving around weighting. The bottom line is to make the golf ball go farther, you must make the clubhead go faster – and lighter enables speed to increase.