The launch angle of a driver is the angle at which the ball is struck into the air from the driver, measured from the ground. Most drivers will have a launch angle of between 11 and 18 degrees under testing. It is important to find the right launch angle to produce the maximum amount of distance from your swing. The perfect launch angle will maximise both carry and roll.
The headsize of a driver is the size of everything below the shaft. It is measured in cubic centimetres. The legal limit for a driver is 460cc set by the R&A.
Moment Of Inertia (MOI)
Moment of Inertia is the term applied to a club head's resistance to twisting when the ball is struck. For example, your swing is a little off and you hit the ball on the toe of the club head. A club head with a higher MOI will twist less as a result of the miss-hit, creating a better chance that the ball will still go where you intended and with less loss of distance. It is a strong indication of the "forgiveness" of a club head - that is, the extent to which a good result can be achieved from a less than ideal contact with the ball. Further increases to 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.
Moment of Inertiais a physical property that can be expressed as a numerical measurement. On April 11 2006, the USGA announced that the maximum allowed MOI has been revised to 5,900 g-cm2 (32.259 oz-in2) with a tolerance of /- 100 g-cm2 . The limit is on moment of inertia around the vertical axis through the club head center of gravity
The COR, or Coefficient of Restitution , is the measurement of the amount of energy transferred between the clubface and the ball at impact. Specifically, the COR measures the how well the ball rebounds off of the clubface. The higher the COR, the more energy is retained and the ball rebounds farther. If it were possible to transfer all of the energy in the clubhead to the ball, the COR would be 1.00 (100%) The USGA has set a maximum COR value that a club can have at 0.83. This means that there can be no more than an 83% energy transfer from the clubhead to the ball.
The R&A currently allow drivers with a COR of 0.89 to be used in general play by amateurs. However as of 1 January 2008 it will reduce to the USGA limnit of 0.83. However for Tour professionals and elite amateurs in the R&A juristiction, the 0.83 limit already applies now.
If you are unsure about your new driver being over the limit you can check our driver review section or go to the R&A's website at www.randa.org where you can find a full list of conforming drivers in the Rules > Equipment section.
Length & Weight
Many people could be forgiven for believing the length and weight of a driver is not important. This is untrue though. Drivers vary from 43-47 inches long typically. Increasing the length of your driver will increase you driver distance, but you will sacrifice control and is recommended only to experienced players. The reason for the increased length is the simple physics that the clubhead has further to travel to the ball, therefore picking up speed for longer. Similarly the lighter the driver, the faster the players swing speed will be, producing more distance. If you desire more control on your drives a heavier driver will offer more control.
A recent breakthrough in driver technology is the incorporation of plugs or weights in the head of drivers. Manufacturers discovered this technology in the late 90s with tungsten inserts that were placed behind the face of the driver to add to the sweet spot. The position of the weight affects the way in which it works. The further the weight is away from the face, the higher the ball flight it will produce. In more recent years, companies have begun adding removable weights. Usually, up to four weights can be placed in the head of drivers to offer players different shapes and velocities. The rules of golf mean that the weights cannot be changed whilst in a round, but can be adjusted between rounds to change the player's ball flight.
Inspired by Tour players and custom fitting demands, many new drivers feature adjustability. In addition to plugs/weights (above), manufacturers have screw hosels to drivers allowing players to remove the head from the shaft, and adjust the lie, loft, face angle. Simply use the tool provided by the manufacturer to unscrew the head, follow the instructions for the desired setting, and reattach the clubhead. The resulting ease of adjustability allows players to alter their ball-flight with immediate results, rather than in the past when different heads would be fixed to corresponding shafts requiring players to test/try several different drivers. Some manufacturers claim the adjustability in their drivers produces up to 75 yards of left-to-right ball flight variance.