What is Bowling Ball RG?
What is RG in bowling?
What are the essential elements you should know!
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Bowling Ball RG
RG stands for “Radius of Gyration” being a measurement of where the bowling ball’s total mass is concentrated as measured from the ball’s axis of rotation.
The more the weight of the ball is located in the center or the core, the lower the RG values.
The more the weight of the ball is closer to the coverstock, the higher the RG values.
The RG measurement can range between 2.460 inches to 2.800 inches.
A bowling ball with low RG, the ball will be within the 2.460 inches to 2.570 measurements.
A medium RG score will put your bowling ball within the 2.570 inches to the 2.680 inches.
And a high RG score will put you above 2.680 inches and 2.800 inches.
Companies tend to provide another bowling ball specification which is the ball’s differential representing the ball’s flare potential (or how much the ball is touching the surface of the lane).
We cover that in another article, be sure to check it out.
What is Bowling Ball RG
The RG value of a bowling ball is defined by the USBC as the measurement of the distance of where the ball’s total mass is concentrated from its axis of rotation without any changes to its moment of inertia.
Said simply, RG (Bowling Ball) is the account for where the mass is located within a bowling ball specifying if the mass is more towards the center or closer to the coverstock or outer shell.
According to the USBC rules, RG in bowling cannot be shorter than 2.460 inches and longer than 2.800 inches.
Just like a football, a bowling ball has an axis of rotation.
For example, if you throw a football as a spiral, it will have a smaller radius than a football spinning end over end.
When the football is thrown as a spiral, it has a lower RG value than when it is thrown end over end.
Another example is with figure skaters.
When a figure skater spins on the ice with their mass concentrated towards the center of their body and their arms tucked in, they will spin much faster (they have a low RG value).
Alternatively, if they spread their arms out and increase their Radius of Gyration, they will not spin as fast.
It’s the same thing with bowling balls.
Depending on how the weight is distributed in the core of the bowling ball (the weight block), the spin on the ball will be different.
The Radius of Gyration will indicate the distance in the mass concentration of the ball over its axis of rotation.
It’s like saying if the figure skater has their arms tucked in (lower RG) or spread out (higher RG).
Why Is RG Important
Understanding bowling ball specs, particularly the RG measurement is quite important if you are looking to have an idea as to your ball’s hooking potential.
Hooking potential is your bowling ball’s capability in curling or moving out of a straight line.
The idea is to use the “hook” to enter the pocket at an angle, maximizing the possibility of a strike.
Now, why is the Radius of Gyration in bowling important?
In summary, low RG bowling balls will produce a “hook” faster or earlier down the lane.
Low RG will help induce an earlier roll and will have less energy towards the end of the bowling lane.
These balls will have a fast and early revolution early on.
On the other hand, high RG bowling balls will produce a “hook” further down the lane giving you more length.
With high RG balls, the ball will enter into a hooking motion towards the end of the alley and will keep more energy for the backend.
These balls will travel in a more straight fashion and will produce their strongest roll pattern towards the end of the lane.
Bowling Ball RG Chart
To have a visual depiction of the RG values of bowling balls, here is an RG chart to help you situate yourself:
| Radius of Gyration (RG) | |
| Low | 2.460” to 2.570” |
| Medium | 2.570” to 2.680” |
| High | 2.680” to 2.800” |
A High RG value is a type of ball where the mass of the ball is concentrated near the cover or the outer shell of the ball (referred to as “cover heavy”).
A Low RG value indicates that you have a bowling ball where the mass is concentrated around the core of the ball (referred to as “core heavy”).
Bowling Ball Differential
Another important aspect to consider is to read the RG along with the bowling ball differential or DIFF.
The differential is a number referring to the ball’s track flare or how much the ball touches the surface of the lane.
The larger the differential, the more a ball has potential for a hook as it touches the surface of the lane more.
Similarly, the smaller the differential, the less the ball has potential for a hook as it has less contact with the surface.
If you consider RG along with the DIFF, you can then better assess the hook potential of your ball.
If a ball has a low RG value, it will naturally want to hook sooner.
If at the same time, it has a small differential (giving it less contact with the surface), that will dampen the hook to happen a bit later down the lane.
Takeaways
What do the numbers on bowling balls mean?
Let’s look at a summary of our findings on bowling ball specs and what they mean.
Bowling Ball RG
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