Clubfitting, and driver fitting in particular, can seem daunting, even overwhelming. And while most of my students get excited about the idea of getting fit, when the time comes they are nervous and often ask if they really need it. The purpose of this blog post is to help you become more comfortable with the fitting process by helping you understand the terms/words that fitters use.

But first a quick reminder about why you need to get fitted for all your clubs: Finding the right equipment can significantly improve your performance on the course; it helps you maximize your potential by playing clubs that suit your unique swing characteristics. An optimal fit can lead to improved accuracy, distance, and overall enjoyment of the game.

Okay, so let’s explore some important terms and concepts involved in a driver fitting. These concepts and principles are what fitters consider when determining the best driver for you.

MOI refers to a club's resistance to twisting upon impact. A higher MOI means more stability, which can lead to straighter shots, especially on off-center hits. This is particularly beneficial for players who struggle with consistency, as it minimizes the effects of mishits. Your fitter will look at your dispersion with your current driver (if you have one) and will recommend a new head that offers a higher MOI to help improve accuracy.

The CG is the point in the clubhead where the weight is evenly distributed. It influences the launch angle and spin rate of the ball. A lower CG helps launch the ball higher with less spin, making it easier to achieve optimal distance and carry. I’ll mention CG again when we talk about Gear Effect.

The COR is a measure of how elastic collisions are between two objects, in this case, the golf ball and the clubface. It quantifies the ratio of the relative velocity of separation to the relative velocity of approach after impact. In golf, a higher COR indicates that the ball retains more of its speed after striking the clubface, leading to greater distance. This factor is crucial in driver design, as it affects how much energy is transferred from the club to the ball, impacting performance and distance off the tee. There are COR limits that manufacturers must work within. If a club exceeds the maximum allowed COR, the club is deemed “non-conforming” and is not legal for play.

This term describes how the driver’s face angle and impact location affect the ball's flight path. When a ball is struck off-center, the gear effect can alter its spin and direction, impacting accuracy. Gear Effect related to CG. When your ball makes contact with the clubface, the ball wants to spin towards the CG.

Practically speaking, what does that mean? Assuming that the CG is in the middle of the clubface, a ball that is hit off the toe of the club will want to spin towards the center of the face, which typically causes the ball to hook. Similarly, but opposite, a ball hit on the heel will also want to spin towards the CG usually resulting in a slice.

If you struggle with a slice miss, your fitter will recommend a driver head that is built with the CG closer to the heel because this will reduce the amount of slice spin you create. If you fight a hook, then your fitter will have you test drivers that have the CG closer to the toe so that you create less hook spin. Many drivers now have movable weights that allow the fitter to adjust CG based on your tendencies.

If all of this sounds crazy technical (and it really is), don’t let it explode your brain. Your fitter will understand these concepts and will use them in making decisions. Your fitter can talk you through how Gear Effect and CG apply to your fitting.
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The lie angle is the angle between the shaft and the ground, and for fitting purposes we are interested in the lie angle at impact. A correct lie angle ensures that the clubface is square at impact. If the lie angle is too flat or too upright, it can influence initial launch direction. Many drivers now have an adjustable hosel that lets you change your lie angle.

Loft refers to the angle of the clubface relative to the ground. It affects the launch angle and spin rate. More loft typically results in higher launches with more spin, which can be advantageous for players needing extra height to clear obstacles.

The length of the shaft influences swing mechanics, control, and distance. A longer shaft can provide additional distance but may sacrifice accuracy. Fitters evaluate a player's swing to determine the optimal shaft length for achieving both distance and precision.

Shaft flex determines how much the shaft bends during a swing. Options range from extra stiff to senior flex. A shaft that’s too stiff or too flexible for a player's swing can lead to inconsistent shots. Finding the right flex ensures that players can generate maximum clubhead speed while maintaining control.

The grip size affects how well a player can control the club. A grip that's too small can lead to over-gripping, causing tension in the hands and arms, while a grip that's too large can inhibit proper hand placement and control. Fitters assess hand size and grip preferences to recommend the ideal grip.

Most driver fittings are conducted using launch monitors, which provide critical data to refine the fitting process. Here are some important metrics:

This is the angle at which the ball leaves the clubface. The optimal launch angle varies by player, but generally, a higher lauch angle combined with the right spin can lead to better carry distance.
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Backspin affects how the ball behaves in the air and upon landing. Too much backspin can result in a ballooning shot, while too little can cause the ball to run out excessively after landing. Fitters aim for a balanced backspin rate for each player's swing.

Apex refers to the highest point the ball reaches during its flight. Understanding a player's apex helps fitters determine if adjustments to loft or CG are needed to optimize distance and trajectory.

This angle describes how steeply the ball descends towards the ground. A proper descent angle ensures that the ball lands softly on the green, increasing the chances of holding the surface.

Carry distance is the distance the ball travels through the air before hitting the ground. This is a critical metric in determining how effective a driver is for a particular player.

Driver fitting is a vital component of maximizing a golfer's potential on the course. By understanding the terminology and metrics involved in the fitting process, players can make informed decisions and work with fitters to find the right driver for their game. Whether you’re a seasoned pro or just starting, investing time in a proper driver fitting can lead to significant improvements in your performance and enjoyment of the game.

Ideas and editing: Coach Karl
​Writing assistance: ChatGPT