Do Long Hitters Get An Unfair Benefit?
April 19, 2006
By Steve Quintavalla, Engineer
Read The Technical Report (PDF)
One opinion often accepted as conventional wisdom is that modern golf balls used on the PGA Tour give an unfair distance advantage to players with very high swing speeds. The thinking is that golfers with very fast swing speeds (115+ mph) have gained a disproportionate amount of distance because modern golf balls only get "activated" when they're compressed at very high swing speeds, especially when struck by modern drivers. Another belief is that ball aerodynamics also result in disproportionately greater distance increase for those with very fast swing speeds.
Let's look at the physics, test results, and the actual PGA Tour driving distance results, to see what the facts really are.
What the Science Says:
Actually, there is no extra distance "bonus" for high swing speeds. This is true for the new tour balls, and all others as well. In fact, distance does not even increase linearly (see below), but rather it starts to fall off slightly at higher swing speeds - just the opposite of the popular misconception To be sure, hitting the ball faster means it goes longer; it's just that you don't get as much bang-for-the-buck at the highest speeds.
Why is that? To answer, let's look at what happens when you hit the ball. At contact, the club transfers some of its energy into the ball, which then speeds down the fairway. Aerodynamic forces - "lift" (which keeps the ball in the air) and "drag" (which slows the ball down) - then determine how far the ball will go.
The coefficient of restitution (or COR) measures how effectively club energy gets transferred into ball speed. The USGA has tested the COR of balls struck by modern titanium drivers at club head speeds from 90 mph (typical for an average golfer) up to 130 mph (faster than the longest players on tour).
It turns out that the COR for all golf balls decreases as clubhead speed goes up (see right). Repeated tests have proven again and again that the "energy boost" at tour-level speeds is a myth. In fact, the ball is less effective at translating energy into distance at higher swing speeds.
The USGA has also tested the aerodynamic properties of golf balls, including all of the balls currently used on tour (up to ball speeds more than 195 mph). Aerodynamic forces on the golf ball rise significantly with ball speed. Though lift (good for distance) is increased, drag (bad for distance) increases even more.
What the Stats Say:
So, here's a question: regardless of what the science says should happen, what actually has happened on the PGA Tour?
Let's consider a couple of snapshots in time: In 2000, the most common ball used on Tour was a high-spinning wound ball and typical drivers were 250-300cc in size. By 2005 Tour players had entirely replaced the wound ball with advanced multipiece "solid" balls, and their drivers were typically near or above 400cc in size. So, how did these equipment changes affect Tour players with different swing speeds?
To answer the question, let's look at the one hundred tour players who were on the Tour in both 2000 and 2005 and whose average driving distance was recorded in both 2000 and 2005 (courtesy: PGA Tour website). For these players, the average distance increase was 11.6 yards. Now, if it was true that these new, high-tech balls and drivers were benefiting the longer hitters the most, we would obviously expect to see that they had the biggest distance increase. However, as the chart clearly shows, this just wasn't true.
Below, we see how players ranked in distance back in 2000 (in groups of 10, so the ten shortest players are at the left, the ten longest at the right): the heights of the bars show how much they increased their distance. In fact, the longest players (in 2000) did not gain the most distance over that five-year period.
Summing it all up: the science, the experiments, and the actual distances from thePGATour all say the same thing: the new balls and clubs used on tour do not give an extra distance "bonus" to players with higher swing speeds.