I have seen lots of writings saying something like “distance is clubhead speed times 2.4,” or maybe “distance is clubhead speed times 2.6.” But it’s not. More properly it is, but only at some specific clubhead speed. So that’s not very useful.Let me give you the correct answer first, then we’ll look more closely at where it comes from and how to use it.
Every increase of clubhead speed by one mile per hour gives 3.16 additional yards. And yes, a decrease of one MPH loses 3.16 yards. For most practical use of this rule, you can just use 3 and be close enough.
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Note that this does not say “distance is clubhead speed times 3.16.” It talks about increase or decrease of distance from where you already are. That is important we’ll see why when we see where this comes from. Here are a few more things you need to know about this “magic number” 3.16.
- It assumes we are talking about driving the ball, not flying irons or wedges.And it assumes that your driver is reasonably well fit to you. In fact, if your clubhead speed changes by much (say, 5mph or more) you should have a competent clubfitter re-check to be sure you are still using the right driver. If you don’t, you might not be getting the extra 3.16 yards per mph.
- It assumes that changing your clubhead speed does not change the quality of impact with the ball.Smash factor matters! A lot! A swing change or equipment change that loses smash factor better gain a lot of clubhead speed to make up for it. We’ll see how much in my next blog.
- It works well for clubhead speeds between 50 and 120mph. Outside that range, the magic number will be lower.
Now that we know the answer (once again, it’s three… 3.16 for the overly precise), let’s look at where is comes from. There’s a little math here. But I checked, and none of what I used is more advanced than eighth grade algebra. You may or may not remember it, but you almost certainly passed a test in it at some point.
Driver distance is very complicated to calculate. It involves iteratively solving six differential equations in three dimensions, and pretty much has to be done by computer. I have a program, TrajectoWare Drive, that does this computation for me — so I don’t have to do the math for that part. I used TrajectoWare Drive to find the carry distance for clubhead speeds every 10mph, with the assumptions above and a few more (like zero angle of attack and a course at sea level, basic stuff).
Then I plotted the distance vs clubhead speed as a graph. Here’s what it looked like.
If we were able to express distance as clubhead speed times some factor (like 2.4), then the graph would be a straight line through the origin (0,0) and the slope of the line would be the factor we need (like 2.4). The red curve we have here is obviously not that. But let’s see what that straight line might look like for a few different clubhead speeds.
The three straight lines in this graph cross the red curve at the proper clubhead speed. But they are different lines with different slopes, so there isn’t one formula of the form, say, distance = 2.33 * clubhead speed. (The blue line in the graph.) That one works… unfortunately only for a clubhead speed of 100mph. You need a different number for each clubhead speed.
But notice that part of the red curve looks very straight.
From about 50mph to 120mph, the red curve looks like a straight line. Let’s draw it again, this time along with the best-fit straight line for that portion of the curve. It’s a straight line, but not through the origin.
I had Excel actually compute the best-fit straight line for the curve, from 50mph to 120mph. The equation came out to be
If I had gone for total distance instead of carry distance, the slope would still be 3.16, but the y-intercept (-85.2 in the equation) would be different.
Whether you are looking for carry distance or total distance, every additional MPH of clubhead speed is worth about 3 yards of distance, for clubhead speeds between 50 and 120mph. This assumes you aren’t changing other stuff besides clubhead speed (that is, same smash factor, properly fitted driver, etc).
If you want to see this in more depth, there is an article with the full analysis on my web site.