RG Differential and RG What Does This Mean?

I will try to address this simply and with as little confusion as possible. I first must tell you I am not a scientist or a ball designer. I am always learning as are you. I am sure some of you have wondered what does some of the numbers on a bowling ball technical sheet mean and how does it affect me, the bowler. Why do I need to know it anyway. First I must address cover stocks and cores. The cover stock is like the tires on a car and the core is like the engine. These two things are what influence the bowling ball motion. You choose a bowling ball to match your style and the lane conditions you bowl on. Because of so many different style bowlers and bowling lane conditions, the ball companies make different types of balls, and are trying to make a ball that will sell. So that is why you see these numbers on a balls specs. sheet. Also, the USBC rates them to have a tolerance.

RG-
RG means Radius Of Gyration. The RG of a bowling ball tells you how soon the core is designed to roll. The lower the RG, the sooner the ball is designed to roll. The lowest allowed by the USBC is 2.43 the highest is RG 2.80. (USBC could change the rule anytime).

The RG Differential (also called just DIFFERENTIAL) -
This indicates the difference between the low RG and the high RG. The Differential indicates the potential for track flare which can be translated into hook potential. The higher the differential, the more hook potential the core possesses. The RG differential indicates the difference between the low RG and the high RG. The maximum differential allowed by the USBC is 0.060. Don’t get this confused with intermediate differential because that is different. This is used in asymmetrical bowling balls to measure the spin time of the bowling ball before drilling.
Note: All numbers on the spec. sheets are before drilling and that is an important factor as the numbers then change.
Ok this is what RG Differential and RG mean. But, the biggest influence in bowling ball motion is the surface of the ball and the force and direction of the bowler’s release. In addition, the condition of the bowling lane must also be taken into consideration...

Now here is a pretty good rule.

A lower RG ball with a low differential will produce an earlier rolling ball with a small arcing motion.
A lower RG ball with a high differential will produce an earlier rolling ball with a larger/stronger arcing motion.
A higher RG ball with a low differential will produce a later rolling ball with an angular backend motion.
A higher RG ball with a high differential will produce a later rolling ball with a strong, somewhat angular backend motion.

On differential:
The lower the differential the closer together the track flare. The higher the differential the further apart the track flare. The cover stock friction on the lane allows this to come together. Coverstock adjustment is needed to adjust to the conditions you are bowling on. Well I hope this helps and does not confuse you too much. Refer to the Recommended Resources section below for more valuable bowling information

Good Luck and Good Bowling.