In a symmetrical ball the thumb hole will be the preferred spin axis (PSA) although it will be a weak PSA compared to the PSAs in asymmetrical balls. In an asymmetrical ball this is the Preferred Spin axis (not the X-axis as it is in symmetrical balls).Īsymmetrical balls will migrate or flare towards the PSA axis as it is preferred. In an asymmetrical ball the main pin is also paired with a second marking min called either the PSA Indicator Pin or the Mass Bias (both names are interchangeable and mean the same thing). With friction the ball would want to migrate to a more stable rolling axis, ultimately the X-axis which rolls perfectly around the pin. The Y-axis would be perpendicular to the X-axis and although it would be relatively stable it wouldn’t be the preferred spinning axis of the ball. It travels through the pin to the opposite side of the ball.
The X-axis follows the most stable and preferred rolling axis of the ball. This PSA access is sometimes referred to as the z-axis because it’s the only access point that is offset the x-axis that remains the same on both sides. In an asymmetrical ball there is actually a single point on this equator line that is called the preferred spin access (PSA) and is marked as a specific point 90-degrees off the pin (or top of the ball). In a symmetrical ball the y-axis is exactly the same all the way around the ball just as the equator of earth is the same all the way around the planet. The “Y-axis” on the other hand is commonly known as the high RG axis of a bowling ball which is exactly 90-degrees offset the X-axis.
This axis travels through the core from the top of to the bottom with the pin being the top of the ball. The “X-axis” is commonly known as the the low RG axis of a bowling ball. What the Heck is RG and Why Should I Care?Įvery bowling ball has at least two axes. Simply put – Asymmetric bowling balls will flare more resulting in a stronger skid/flip ball reaction – frequently this means a stronger back-end with a comparatively weaker mid-lane read. When a bowling ball’s differential is higher the ball has the potential for more flare.Īlthough any ball with a high differential has the potential for maximum flare on a bowling lane any random asymmetrical ball in your bag will usually flare more than the random symmetrical ball because they naturally have higher differential values as a rule of thumb. Symmetric balls tend to have low differential whereas asymmetric balls tend to have high differential – the difference between the maximum RG and minimum RG of a bowling ball. This is my personal cheat sheet to bowling ball specifications.Įvery ball made these days is pretty complicated so understanding these specs (even at a very basic level) will go a long way to improving your understanding of ball motion and the potential a ball has to improve your arsenal.įor starters their are two different types of balls: symmetric and asymmetric.