Like our website
Tweet @bowlingball
Follow @bowlingball
Use and distribution of this article is subject to our terms and conditions
whereby's information and copyright must be included.

Symmetric Bowling Balls, Originally Posted: 4/25/2012; Updated: 5/2/2024

Understanding symmetric bowling balls can be a help in selecting your next bowling ball. Bowling ball symmetry varies from ball to ball based upon certain factors engineered into the ball construction process. Familiarizing yourself with symmetric bowling balls is also a step in understanding how to control the back-end bowling ball motion on given oil conditions.

Examining bowling ball symmetric core designs involves a quick comparison to asymmetric core bowling balls and also involves scientific descriptions and terms of elements involved in bowling ball construction. Let's examine some of these terms such as bowling ball symmetry and try to clarify how these terms relate to bowling ball motion:

1. Symmetrical Core (undrilled) - A ball where the RG (radius of gyration) values of the Y (high RG) and Z (intermediate RG) axes of the ball do not differ by more than 5% of the total differential of the ball.

2. Asymmetrical Core (undrilled) - A ball where the RG (radius of gyration) values of the Y (high RG) and Z (intermediate RG) axes of the ball differ by more than 5% of the total differential of the ball.

As a quick sidebar, it has been proven through United States Bowling Association (USBC) field studies that all drilled bowling balls are asymmetrical, whether they are symmetrical or asymmetrical before drilling. Therefore, the degree of symmetry influences ball motion after the initial skid phase.

Let's quickly define other common scientific terms used when rating length and hook potential in new bowling balls:

1. The term differential in a bowling ball can be defined as the difference between the maximum and minimum Radius of Gyration. wishes to add that the higher the differential rating, the greater the track flare potential and the more angular motion the ball will produce from the break point to the pocket. The lower the flare potential, the ball will yield more of a smooth arc motion on the back end of the lane.

2. RG is measured in inches and is the distance from the axis of rotation at which the total mass of a body might be concentrated without changing its moment of inertia. wishes to add that the RG rating describes the distribution of mass in a given bowling ball and RG is an account of the location of that mass inside the given bowling ball.

3. Total Differential is the difference between the X (low RG) and Y (high RG) axes values of any bowling ball. Intermediate Differential is the difference in radius of gyration between the Y (high RG) and Z (intermediate RG) axes on the bowling ball.

4. The differential of RG measurement indicates a given bowling ball's track flare potential. The higher the number the greater the track flare potential.

5. A key to ball motion is intermediate differential which is the measure of a bowling ball’s degree of asymmetry. Differential ratio is simply defined as the intermediate differential divided by the total differential.

6. Symmetrical drilled balls yield small differential ratios. Small differential ratios will produce a smooth, controllable motion. The larger the differential ratio, the more asymmetrical the bowling ball. Conversely, the smaller the differential ratio, the less asymmetrical the ball.

Enough about the science - are you confused yet? It is sometimes difficult to understand how the engineers describe bowling ball symmetry and ball motion in scientific terms.
As a bowler and with the desire to keep things as simple to understand as possible, you need to know:

1. The degree of symmetry in any given bowling ball is developed through the core design process.

2. The more symmetrical a given ball is rated, the less aggressive is the hook potential rating and a smooth or mild arc motion can be generally produced in back-end of the lane.

3. The more asymmetric a given ball is, the higher the total differential and the greater the hook potential is and the more aggressively the ball should react on the back-end of the lane given use of the same coverstock in both examples.

When you set out to buy a new ball, pay attention to the following:

1. The coverstock is always the first consideration in choosing a new bowling ball. The coverstock is a chief factor in developing the length potential rating in a given bowling ball and how to match with the lane oil condition you encounter.

2. The length potential rating determines ball skid length and how a given bowling ball will react in the mid-lane

3. The hook potential rating which is also primarily based on the core design (as is length potential) will guide you in how aggressively the ball will react on the back end of the lane.

Coverstock aggressiveness, length potential, and hook potential are your key factors when choosing a new ball. This is why manufacturers are precisely matching given coverstocks to specific core designs so the effect produces the overall ball motion planned in the R&D phase by leading equipment manufacturers.

You can view ​some examples of symmetric bowling balls readily available at here. has made an effort to provide useful information about bowling ball technology free of charge to our community visitors. Our hopes are in helping each of you to gain further knowledge about the highly technical world of bowling ball design.

If you wish to view some of the latest bowling ball equipment hook potential ratings available in the market today, kindly reference our Perfect Scale® rating feature which helps our shoppers compare the latest bowling balls on the market today.
We also recommend you consult your local pro shop professional before choosing your next bowling ball so you may discuss the important drilling layout options to augment your new bowling ball and help you achieve a desired ball motion. has become the No. 1 "e-tailer" of choice for bowling equipment by the consumers of America. If you are ready to make a purchase, simply follow the easy online order instructions. Thanks for visiting

Click here to shop smart deals Need Help? Click here to access our contact information.
WeeklyContestText Click here to shop all Pyramid bowling balls