RG and Differential. What they mean

[billf]

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.

[ArtVandelay]

I think you make a lot of sense. I had researched everything i could before i bought my ball, but you went into better detail.

Kind of unrelated, but how do you think this would apply to a ball like the boom-Rang?

I like the concept of the ball but ultimately shied away from it due to its different nature. I wanted something more familiar. Do you have any thoughts?

[billf]

The Boom-R'ang is the future of symmetrical core balls (my opinion). Many companies have begun making balls with symmetrical cores with very strong back end moves (Nexxxus, Marauder among them). Personally, I like the combination of these balls being polished to help clear the heads but with such strong cores that they have a big reaction on the back end. However, if all a bowler is comfortable with is playing straight up 10 or 12 then these balls would be too much for them.
Also, balls such as these that are designed to go long and hook hard should be drilled to compliment that. Going with a layout that has a large VAL angle (which smooths out the hook) would essentially ruin the design of how the ball was intended to be used. This is akin to a Stroker trying to play the deep inside part of the lane...just doesn't make sense. That all being said, there is nothing wrong with a Stroker starting at 10 where they are comfortable and letting the ball go out to the 5 or even the 3 board and letting the ball come back on it's own, as designed. This would greatly increase the entry angle, carry and strike percentages.

[e-tank]

I found this post very informative as this isnt something i took much time to research myself. I just knew that RG differential= hook potential. That Boomerang ball looks awesome btw!

[75lockwood]

Great Writeup, thanks Bill!

FAQ'ed!

[striker12]

thanks bill i asked my proshop operator about the RG a few weeks before Christmas and he told me what you said but you put more in there for me to learn thanks.

[Greenday]

Welp, that explains a lot. And definitely makes a lot of sense with the balls I have.

[BrandonKR]

I only started learning about all this a couple months back, and this definitely re-enforces what I've learnt. Great writeup

[JerseyJim]

The Boom-R'ang is the future of symmetrical core balls (my opinion). Many companies have begun making balls with symmetrical cores with very strong back end moves (Nexxxus, Marauder among them). Personally, I like the combination of these balls being polished to help clear the heads but with such strong cores that they have a big reaction on the back end. However, if all a bowler is comfortable with is playing straight up 10 or 12 then these balls would be too much for them.

Actually LaneMasters/Legends only made symmetrical cored bowling balls that had a large range of motions for years. Unfortunately they went under a few years ago. I liked them because they didn't create a dozen new balls each year, and their balls never tracked out.

[eugene02]

Luckily I took time to read.. well.. hell.. I didn't know any of this =P but still... heh! nice one bill..