Balance Holes


A balance hole is an extra hole in the bowling ball that is not used for gripping purposes. Balance holes are primarily used to make the ball static weight legal to the current USBC Equipment Specifications and Certifications Manual if they are outside the legal limit after drilling. Once a bowling ball has been drilled, there are still options to fine-tune the reaction for the bowler. This article is going to look at how balance holes can be used to alter the reaction of a bowling ball.

Traditional thinking

Balance holes can influence ball reaction depending on the size and the location of the hole. Before reading this article, take a look at your current equipment. Do any of your bowling balls currently utilize a balance hole? If so, was there any thought put into the location of it, or was it simply to make the ball static weight legal? You may notice that you really like a ball with a certain location and size of balance hole, but it might not be your favorite on a different ball. Why is this? Let's examine.

Traditionally, balance holes were presented in very simple terms. Historically, the higher the balance hole is in relation to the midline, the more it decreases the flare potential of the bowling ball. The lower the balance hole is in relation to the midline, the more it increases the flare potential of the bowling ball. Figure 1 illustrates this. While this is mostly true, there can definitely be some exceptions. Not all balance holes in the same location are going to have the same effect on the ball. There are other variables that are going to influence how they alter the bowling ball's performance.

The term "RG" refers to the radius of gyration - a very important bowling term to become familiar with. This basically tells you how much of the mass is located towards the center of the ball.

Low RG's means more of the mass is centrally located. Higher RG's mean that more of the mass is located away from the center. Lower RG balls are going to require less energy to change direction. They will transition faster and roll earlier. Higher RG balls require more energy to change direction. They will transition slower and roll later.

Every ball is going to have both a low RG and high RG axis. Take a look at Figure 2. It's important to note that the pin is the surface designation for the low RG x-axis of the bowling ball. In general, 6 3/4" from the pin is going to be the high RG y-axis of the bowling ball. The distance from the x-axis to the balance hole is going to be crucial in determining how much and what kind of effect that the balance hole has on the reaction of the bowling ball. Shorter distances (3" or less) to the x-axis are going to decrease reaction. Longer distances (4" or more) to the x-axis are going to increase reaction. Distances somewhere in the middle are going to have little to no effect. Why does this occur? Let's take a look.

the difference in RG's

Every hole that you introduce to a bowling ball is going to raise the RG of the ball in that particular location of the hole itself. We know that the pin designates the low RG axis on the entire ball. Figure 3 represents a 15lb Torrent. Looking at the numbers, a Torrent in this weight has a low RG of 2.56 and differential of 0.044. This means at the location of the pin, the RG of the bowling ball is going to be 2.56. If we go approximately 6 3/4" away from the x-axis, we will find the y-axis. The y-axis is the high RG axis of the bowling ball. This is essentially a 90° angle from the top to the side of the core. The difference between these two axes represent the total differential of the ball. Using some simple math, we can calculate what the high RG axis of an undrilled 15lb Torrent is. 2.56 (Low RG) + 0.044 (Differential) = 2.604 (High RG). It is important to note that the RG of the ball is going to change as we move across the surface of the ball. Somewhere in between 0 and 6 3/4", the RG will be somewhere between 2.56 and 2.604. The shape of the core primarily influences this. Now that we know the RG's of the Torrent, we can take a look at how balance holes are going to influence them.



Distance from the x-axis

Let's start with hole placements with shorter distances from the x-axis. Imagine putting an extra hole directly through the pin as an extreme example. We know that introducing a hole into the ball is going to raise the RG of the ball in that particular spot. The x-axis is the lowest RG spot on the entire ball. If we add a hole to it, we are raising the RG of the lowest RG spot on the ball. This makes the lowest RG spot on the ball higher and closer to the high RG axis. This is lowering the total differential between the two, which makes the ball weaker and respond slower as it transitions down the lane. Think about where the mass is being taken out of the core. The pin is designating the top of the core. If we drill a hole directly through the pin, we are taking more mass out of the top of the core. This essentially makes the core shorter, which lowers the total differential and raises the overall RG.

Now let's take a look at hole placements with longer distances from the x-axis. Imagine putting an extra hole 6 3/4" away from the x-axis. As always, when introducing a hole into the ball, that hole is going to raise the RG of the ball in that particular spot. Approximately 6 3/4" away from the x-axis is the high RG axis. If we put a hole on the high RG axis, we are raising the RG of the already high RG axis of the ball making it even higher. What is this going to do to the overall differential? The low RG axis remains unchanged, but now the high RG axis is even higher. The total differential has increased and the RG has remained lower. Imagine where the mass is being taken out of the core with the hole 6 3/4" from the pin. All of the mass will be removed from the side of the core. This is going to make it skinnier than it was before compared to its height. This will increase the total differential and keep the overall the RG lower.

Finally, let's take a look at medium distances. If we put an extra hole at 3 3/8"away from the X-axis, we are precisely between both the low RG axis and high RG axis. This is going to have little effect because we are taking mass out at a 45° angle relative to each axis. We are taking mass out of the top and the side which cancels out the effect. If we get farther than the 3 3/8" distance, we remove more mass from the side. If we get closer than the 3 3/8" distance, we remove more mass from the top. Each of these effects have been outlined above and should make sense.

Sizes are pretty self-explanatory. As you can imagine, the larger and deeper the hole, the more effect the hole will have on the reaction of the ball. This is because we are removing more mass out of the core. This means there are a lot of options when it comes to size and depth. I always suggest starting with a smaller hole because you can always increase the size based on what you see from the initial ball reaction.


Position on the arc

The final variable to look at is the position of the balance hole on the arc. Let's imagine that we put an extra hole in the ball 5" from the pin. There are many different positions on the ball that are 5". Looking at the Figure 4, we can place a balance hole anywhere on this arc and it will remain 5" from the pin. The further out we put the hole towards the VAL, the more we are going to smooth out and slow down the reaction. This happens because the holes are further apart. The closer we get the hole towards the thumb, the faster this ball is going to transition. This happens because the holes are closer together creating a larger intermediate differential after drilling. It is important to note that you always need to make sure that tracking issues won't occur when determining where to place the balance hole. You will always want to throw the ball first and make sure you aren't placing the balance hole near any track flare. Keep in mind, if you are using a flare increasing hole (4" or more), the ball is going to flare more after the hole is drilled. You will need to put the hole further away from the flare rings.



Looking at balance holes like this makes it easier because it gives you consistency from ball to ball. The mass is being taken out of the same spot on the weight block to create a more consistent reaction regardless of the differences in layout. In Figure 5, the ball on the left is drilled 3 x 4 x 1 and the ball on the right is drilled 6 x 4 x 3. If both balls were to have a balance hole located on the PAP, the balance holes are not going to have the same effect on each of the balls. It's going to increase the total differential and lower the RG on the 6 x 4 x 3 ball because the balance hole is 6" from the pin. On the 3 x 4 x 1 ball, the balance hole is going to have less of an effect because it is drilled in the neutral zone of 3-4" from the pin. Keep in mind, all of this information is relative to all of the other pieces of the puzzle. Remember that Pin-to-PAP distance is going to be another variable influencing the reaction. Clearly a ball with a 6" pin-to-PAP distance is going to be cleaner through the front part of the lane and flare less. The location of the hole is one of the secondary factors that goes into ball reaction.


symmetrical verses asymmetrical

The last thing we cannot ignore is the effect of hole placement on a symmetrical versus an asymmetrical core. Take a look at Figure 6. Remember that an asymmetrical ball can be fine-tuned even further because of the presence of the PSA, or the preferred spin axis. The closer the balance hole is drilled to the PSA, the higher the intermediate differential is going to become. The ball is going to transition faster because it has a higher intermediate split. The further the balance hole is drilled from the PSA, the more intermediate differential you are drilling out of the ball. Essentially, you are drilling out some of the asymmetry which makes it transition slower as a symmetrical ball would. All the other principals aforementioned are the same regarding balance hole distance from the x-axis.

Essentially, if we put a 1 1/4"  hole 6 3/4" away from the pin and drill it 3 1/2" deep, we are going to significantly increase the total differential and lower the RG of the ball. This is going to result in it transitioning much faster and hooking more front to back and right to left overall. If we put a 1 1/4" hole through the pin drilled 3 1/2" deep, we are going to significantly decrease the total differential and raise the RG of the ball. This is going to result in the ball transitioning much slower and hooking much less front to back and right to left. If we decrease the size or the depth of these holes, we will reduce the impact that they had in their respective locations.


In summary, you can really see how much of an effect can be created using different balance hole locations and sizes. Hopefully now, you have a better understanding of how balance holes further from the x-axis increase flare potential and balance holes closer to the x-axis decrease flare potential. Keep in mind that there are many pieces to the puzzle that is laying out a bowling ball. Some are more influential than others. This article strictly looks at the effects of balance holes and keeps all other variables constant. Learning more about how these variables work together to create good ball reaction is crucial to understanding what your ball is doing as it transitions down the lane. Knowledge is power - put them all together and you've got some serious power.

Always remember: not all balance holes are created equal!

Symmetric vs Asymmetric Cores

Knowing whether you need a symmetrical ball or an asymmetrical ball for the next piece of your arsenal is more important than you may think. Understanding the difference between the two can be a daunting task even for the seasoned professional, but once you have familiarized yourself with the main factors engineered into the ball construction process the sport becomes much clearer and adjustments become easier. Please keep in mind, however, that the information which follows may lead you to your nearest bottle of aspirin! It can be quite technical in nature, so don’t be alarmed if you need to re-read this article a few times before it starts to make sense.

The term differential is the common nomenclature for the difference between the maximum and minimum RG values. The larger the number, the greater the flare potential becomes for the bowling ball.

The radius of gyration, or RG as commonly known, is a measurement in inches from the axis of rotation at which the total mass of a body might be concentrated without changing its moment of inertia. Low RG balls rev up faster and more easily, creating more ball motion, or change of direction.

Total differential (flare potential) can be described as the difference between the X (low RG) and Y (high RG) axes of any bowling ball, symmetrical or asymmetrical.

Intermediate differential is typically only expressed on asymmetrical balls and is the difference in the RG between Y (high RG) and Z (intermediate RG). Intermediate differentials exist on most symmetrical balls, but is not large enough to make a significant impact on the ball’s overall motion.

Differential ratios mandate how asymmetrical a ball is and can be found by dividing the intermediate differential by the total differential. Balls with a larger ratio have a higher degree of asymmetry. Symmetrical balls have the lowest differential ratios in the industry.

There's a Time and Place

A symmetrical core has an 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. An asymmetrical core is a ball where the RG values of the Y and Z axes of the ball differ by more than 5%. It’s generally accepted that symmetrical drilled balls have a smooth, controllable motion. Asymmetrical balls have a defined, angular shape downlane that respond to friction quicker than symmetrical balls, given the same coverstock composition and preparation. All balls, symmetrical or asymmetrical, become asymmetrical after drilling. Simply put, asymmetrical cores are not in equal proportion top to bottom like a symmetrical core is.

Asymmetrical balls can exhibit large amounts of track flare even with long pin-to-PAP (positive axis point) distances. A 6″ pin-to-PAP distance layout on a symmetrical ball will typically result in a very low-flaring ball. In a strong asymmetrical, however, a 6″ pin-to-PAP distance layout might result in a very high-flaring ball. This is the critical difference between symmetrical balls and asymmetrical balls. This leads to another interesting conclusion: asymmetrical balls can, in general, provide a ball driller with more reaction options than symmetrical balls. Symmetrical balls have only two ball motion "tuning parameters": pin-to-PAP distance and pin buffer. Asymmetrical balls add a third variable to the equation in the placement of the PSA (preferred spin axis) in relationship to the bowler’s PAP. The higher the undrilled intermediate differential is, the more significant the PSA position becomes.

Bowlers who favor the use of an asymmetric core need a little extra help curving the ball. These balls rev up fast and finish strong with a more aggressive movement downlane. Asymmetrical balls are great for heavy amounts of oil or longer patterns which don’t provide a lot of friction while symmetrical balls are typically smoother and yield a benchmark type of reaction that are more controllable. Symmetricals have two principal moments of inertia (X and Y axes) and asymmetricals have three (X, Y, and Z.) This greater degree of asymmetry is responsible for the highly dynamic moves asymmetrical balls can create.

And finally, don’t forget that there has to be a proper marriage between cover, core, and layout for the ball to react optimally, but we will save that for a later discussion.


Knowing Your Roll

Why It's Important

There are many variables that can affect the way your ball rolls. Some are related to the way you release it and your unique delivery. Other variables can be credited to that evil lane man and how he conditions the lane. Then there are factors that are above and beyond anyone’s control, and, no matter how hard you try, you cannot change them. We are going to discuss the subtle distinctions in how you roll the ball that play a bigger role than you might think. Understanding these characteristics will help you in choosing your next ball and, furthermore, help your pro shop operator decide a layout for your brand new toy.

Did you know that your ball actually decelerates as it travels down the lane?

The chemical composition in conjunction with the surface preparation of the coverstock matters greatly. A solid coverstock with a low grit surface texture will lose speed at a higher rate than a polished, pearlized coverstock. Friction reduces ball speed, so this actuality is highly linear with that of wood lanes or lanes that have not been oiled in a long time. In the published Ball Motion Study conducted by the United States Bowling Congress, the ideal bowling ball speed is about 17 miles per hour measured at impact with the pins and about 20-21 miles per hour when the ball is released onto the lanes. Bowlers with high ball speeds and without the revs to match can be considered “speed dominant.” They will typically favor more aggressive surfaces and layouts to help their ball pick up sooner on the lane. “Rev dominant” players with slower ball speeds typically like less aggressive balls, layouts, and surfaces to help prevent their ball from overreacting.


What is rev rate?

Rev rate is a calculation of the amount of revolutions a bowler imparts on a ball. The common unit used is revolutions per minute, or RPM. Over the years, bowlers have generalized the RPM gamut into three categories: stroker, tweener, and cranker. Understanding your rev rate (and its relationship with your speed, axis tilt/rotation) is important because it helps to categorize your specific needs as a bowler. Knowing what type of ball to buy, what techniques need to be applied, or the type of wrist device needed all depend heavily on your rev rate.


What is axis tilt?

Axis tilt is the vertical angle at which the ball rotates. Commonly known as spin, axis tilt is determined by the position of the thumb during the release. If the hand turns too early, the thumb exits on top of the ball. Bowlers with a high degree of axis tilt will be able to see the top of their hand during the release and follow through. The resultant path of a ball with a higher degree of axis tilt is extended and the amount of backend potential is reduced. Oily lanes become quite difficult when the core is rotating in a vertical fashion, but is actually favored on drier lanes. Being able to have the thumb exit at the bottom of the forward swing minimizes axis tilt. The lower the axis tilts, the sooner the ball will enter its roll phase before making impact with the pins.

Axis rotation is the horizontal measure of the angle of the ball's revolutions, and much like axis tilt, it is also determined by the bowler’s release. Axis rotation is commonly known today as side roll. When the ball has no axis rotation, the fingers exited directly underneath the ball at the 6 o’clock position. End-over-end roll (0° of axis rotation) removes all hook potential from the ball regardless of the amount of revolutions, speed, or lane conditions. High amounts of axis rotation (90° of rotation) will cause the ball to skid further, but unlike axis tilt, will cause an intense hook angle at the breakpoint.

Players with high amounts of axis rotation will favor drier lanes, and lower amounts of axis rotation usually like more oil. Higher amounts of friction will cause the ball to lose axis rotation at higher rates. Initial axis rotation, ball speed, axis tilt, and lane friction all dictate when side revolutions become end-over-end revolutions. Generally speaking, balls skid, then hook, then roll. Less rotation will shorten the skid phase and get the ball into the hook phase earlier, while maximum rotation will extend the skid phase of the ball and increase its hook potential down lane. Manipulating your axis rotation is a valuable tool because it will change the ball’s reaction while still allowing you to stay in the same part of the lane and use the same break point. Ideally, you would like to limit lateral moves on the lane because it forces you to make multiple adjust­ments. And often, particularly on challenging conditions, the zone you’re going to have to play and the break point are pretty defined.

Through practice, you can alter or enhance your ball speed, rev rate, axis tilt, and axis rotation.  The best bowlers in the world have the ability to manipulate any and/or all of these at a moment’s notice. Technology of the sport today only enhances the subtleties of your game. Rubber balls and wooden surfaces did not place an emphasis on shot making versatility.  Ball technology and oil patterns of the modern era force quick-changing conditions and different parts of the lane to be utilized that were not in play thirty years ago. Knowing your roll is more important now than ever before.

Timeless | In Your Words

Timeless | In Your Words

"Today finally bought a new ball in over a year! Decided to go with the new Timeless that just came out yesterday! I pinned down the ball just below the ring finger hole. This ball is INSANE! It isn't the most hooking ball, but that is what is good about it! It's not too aggressive but not so it barely hooks. This ball has a lot of back-end which is something new in my arsenal compared to my other balls. When I first threw the ball I kept on moving left and left tell I finally hit a target area to strike! Rolling my first several games with a 247,235, and mid 220's!" - Cale Rusch

"Tonight, my team won our high school division!! And to make it even better, I was throwing my brand new Timeless! Absolutely love it!" - Brittany Ahlgrim

This ball is INSANE! It isn't the most hooking ball, but that is what is good about it! It's not too aggressive but not so it barely hooks.

"Today was night one with my Timeless. O... M... G... That ball does not quit! Used it from game 1 - 3... Get the ball out a board it creates killer carry. Get the ball a bit deep in the pocket and watch the pins fly." - Thomas Musante
"I brought out the new Timeless tonight. It is amazing. 242, 278,268 for 788... Extremely clean through the heads, non violent off the spot, and has a strong continuous roll through the pins." - Michael Reid

“The new #stormtimeless it gets through the heads really smooth, and is super strong off the spot. I find with the dual drive weight block I can get away with a lot of light shots like this without ugly pinfall, after one shot I could tell this was gonna be a winner. #stormnation” - Malcolm Jacobson (Mj)