What they are, how to measure them, and how (and why) they affect your ball’s motion

Almost every day, I feel like I see or hear something that is completely incorrect about axis rotation or axis tilt. Sometimes, people just mix up the two terms and say “tilt” when they should have said “rotation.” Other times, I see people completely misunderstand the effect that axis rotation and axis tilt have on the bowling ball. And, other times yet, I see people very inaccurately describe why axis rotation and axis tilt affect the ball the way they do.

To be fair, I should say that this can be a difficult topic. I remember spending many, many years being confused myself about the mysteries of ball roll, and I never could find answers that satisfied me. As I look back, it’s easy to see why: vague definitions, misinformation, and completely invalid explanations—even though always very well-intentioned—are unfortunately the norm when it comes to this topic.

The goal of this article is to clear up whatever confusions you might have related to axis rotation and axis tilt. We’ll start by defining what axis rotation and axis tilt are, in hopes that you will never mix them up again. We’ll then cover how you can measure your own axis rotation and axis tilt angles. This can be an important first step in knowing whether or not you have a problem that deserves some attention. And, finally, we’ll go in-depth on how and why axis rotation and axis tilt affect the bowling ball as it travels down the lane, hopefully clearing up some serious misconceptions along the way.

What are axis rotation angle and axis tilt angle?

When a bowling ball is released, a certain type of “rotation” is created: as the ball leaves the bowler’s hand, it rotates about a specific axis, and it rotates about that axis at a specific speed. The speed of the ball’s rotation is its rev rate. The axis the ball is rotating about is set by the bowler’s axis rotation angle and axis tilt angle.

Axis rotation angle

In very simple terms, axis rotation angle can be thought of as a measure of how much “side roll” a bowling ball has. Slightly more technically, axis rotation angle is as a measure of how the ball’s axis of rotation is oriented relative to its direction of trave

I am surprised how often the “free” pendulum swing concept continues to be articulated today as a gold standard component of an outstanding physical game. In truth, when reviewing how the body works best, the concept of a pendulum swing is not consistent with good biomechanical movement.

Specifically, the range of motion of the shoulder joint associated with attempting a pendulum is a recipe for shoulder injuries due to the very limited movement in the backswing. It also reduces swing height, which lowers potential energy production.

From an anatomical and biomechanical perspective, an abducted upswing—one that moves to the side of your body—will be a catalyst for a freer swing, and it has the potential to lead to a significantly higher swing. With a higher swing, a bowler can increase the production of energy that can then be transferred to the ball. Moreover, a swing that moves to the side of your body will return toward the body and under the head naturally in the downswing, increasing directional accuracy. The bowler implementing an abducted upswing must align the shoulders at the top of the swing in order for the downswing to move into the body and be throw in the direction of the lane.