If you’ve been paying any attention at all over the last couple of months, you’re likely already aware of the recent USBC rule modifications affecting how bowling balls can be drilled. Just to recap, here are the relevant changes1:
- Balance holes will become illegal effective August 1, 2020. If you have any bowling balls with balance holes that you wish to use in USBC-sanctioned competition on or after that date, you must have the balance hole plugged.
- Starting August 1, 2018, balls that do not have balance holes (including balls with balance holes that have been plugged) are allowed to have up to ±3 ounces of static imbalance in all directions (side, finger/thumb, and top/bottom).
- From August 1, 2018 until July 31, 2020, balls that do have balance holes are limited to the “old” static imbalance rules of ±1 ounce for side weight, ±1 ounce for finger/thumb weight, and ±3 ounces for top/bottom weight.
The bottom line with these rule changes is that there is essentially a two-year “phasing in” period that gives bowlers time to adjust to the new rules. If you so desire, you can start drilling balls right now that conform to the new rules (no balance holes, but with looser static imbalance limits). Or, for the time being, you can continue drilling balls that conform to the old rules (with balance holes, but with the old, stricter static imbalance limits). Also, bowlers now have the option to start plugging their balance holes in preparation for the August 1, 2020 balance hole ban. You certainly don’t have to do this right away—you have almost two years before balance holes officially become illegal—but it is certainly an option for people who want to start moving their arsenals in the direction of the future rules.
In my last article, I addressed the topic of static imbalance in quite a bit of detail. If you haven’t yet read it, I encourage you to do so now, as much of that article is relevant to what follows. In this article, I’ll focus on the other piece of the puzzle: balance holes. We have a lot of ground to cover, so let’s get right to it.
First of all, don’t panic!
If you read my last two articles (here and here), then you already know that I’m very much not a fan of the balance hole elimination rule change. I think it’s quite pointless, and I believe that it will prove to be completely ineffective in producing the outcomes outlined by the USBC2.
In most cases, for balls that already have balance holes, plugging them isn’t going to make much of a difference in terms of on-lane performance. And, when you go to drill your next new ball, the fact that you can’t use a balance hole just isn’t going to significantly change the maximum amount of performance you can get out of it.
We’ll talk more about all of this in detail below, but the bottom line for concerned bowlers is that there isn’t much to panic about when it comes to this new rule change. In short, don’t worry: your ball will probably still hook without a balance hole.
But how can I say all this? Didn’t the USBC just do three years of research that proved balance holes are a problem that needs to be fixed? Didn’t they just prove that eliminating balance holes will reduce the hook of bowling balls by two boards?
In my opinion, no and no.
I’ve read every last word of the USBC’s recently-published research3 on this topic—over 100 pages of information—and they simply don’t make a compelling case in support of their narrative that eliminating balance holes will “help maintain the playing environment by reducing overall hook by approximately two boards4.”
I simply don’t believe that a traditional flare-increasing balance hole (such as a P3 or P4 hole, to use the terminology of the popular Gradient Line Balance Hole system5) creates a significant increase in hook in an already-high-flaring bowling ball. This is actually fairly straightforward to test and demonstrate. Brunswick did it more than 10 years ago6. Storm published a test that showed this just a few weeks ago7. And, I’ve done this kind of test myself—numerous times—both in the real world and in the world of physics-based ball motion simulations. The result is always the same: adding a traditional flare-increasing balance hole to an already-high-flaring bowling ball does not make it hook significantly more, all other things equal.
But, this is not to say that balance holes—in general—do nothing to the performance of bowling balls. That’s not what I’m saying at all. In some cases, balance holes do make balls hook significantly more than they did without the hole. And, in some other cases, balance holes do make balls hook significantly less than they did without the hole. But, in a lot of situations, they just don’t have as significant an effect as many bowlers seem to believe.
Let’s look at the theory behind this—along with some examples—so that you can gain a better understanding of what to expect as you transition into life after balance holes over the next several years.
Basic balance hole theory
Most everything you need to know to understand balance holes and their impact on ball performance has already been covered in my previous article on this topic. In case you don’t feel like re-reading it, here’s a brief recap8.
Balance holes can no doubt have a strong effect on the mass properties of the bowling ball, and that can no doubt have a strong effect on how much track flare the ball has. But, the extent to which those things affect the ball’s on-lane motion varies quite a bit. In other words, in some cases, a giant flare-increasing balance hole will make a ball hook significantly more. But, in other cases, that same giant flare-increasing balance hole might make it hook slightly less. This might sound confusing, but—as I said in my earlier article on this topic—not all identical balance holes are created equal. To put it another way, not all identical balance holes create the same effect on the ball’s motion.
One important key to understanding balance holes is to understand the very non-linear relationship between track flare and on-lane performance. “On-lane performance” is a vague term, of course. But, to keep things simple, let’s think of this term as primarily meaning total hook. Track flare affects total hook approximately as shown below.
To summarize the above graph, total hook increases as track flare increases, but a point of diminishing returns is eventually reached at which point additional track flare results in ever-diminishing amounts of additional hook. On the left portion of the above graph, each of the ball track’s oil rings overlaps the previous one by some amount. This overlapping of adjacent oil rings reduces the amount of friction the ball experiences. As track flare increases (moving to the right on the graph), the flare rings widen, resulting in less oil ring overlap and more exposure of fresh ball surface to the lane, which results in increased friction. But, at some point, the flare rings become fully separated, and further separation begins to have a very diminishing effect on the amount of friction the ball creates.
What this means is that one of the keys to understanding how a balance hole will affect your ball’s motion is to consider where the ball is on this track flare spectrum prior to adding the hole, and where it will be on this spectrum after adding the hole. We’ll look at a handful of examples of this below, in the context of balance hole plugging.
But, before we do that, it is important to mention that track flare isn’t the only thing influenced by a balance hole that affects the ball’s motion. There are also the effects that the balance hole has on the ball’s RGs, its static imbalance, and its overall mass. In most cases, these effects all tend to be fairly small from a ball motion standpoint, whereas the effect of differences in track flare can either be very large or very small, depending on the situation.
Balance hole plugging examples
Let’s look at a few examples of what happens when various types of balance holes are plugged. As per the usual for me, these examples will be done using a bowling ball drilling and on-lane motion simulation software tool that I’ve been designing, developing, and validating for the better part of the last decade.
I hope these examples will give you an improved understanding of what to expect as you prepare your equipment for the 2020 balance hole ban.
We’ll start with a fairly typical scenario—one that might look a lot like some of the balls in many of your bags today. Put simply, this is a high-flare ball and layout that use a flare-increasing balance hole.
Since this ball uses a flare-increasing balance hole, we would expect the ball’s differentials to go down upon plugging the hole. And, that’s exactly what happens, as the plugged-hole ball shown below has 0.009″ less total differential than it did with the balance hole drilled.
But, plugging this ball’s balance hole does not make it hook less, as many of you might have expected. In fact, the plugged-hole ball will hook just a tiny bit more than the non-plugged ball.
Why does this happen? Well, let’s analyze it. With the balance hole, this ball flared approximately 9 inches in total (which includes the amount it flared on the dry back end). After we plugged the hole, it flared noticeably less—about 8 inches—but that’s still quite a large amount of track flare.
When you take a ball from 9 inches of track flare (which is a lot) down to 8 inches of track flare (which is also a lot), there is almost no reduction in the amount of friction the ball is able to create with the lane. Why? The ball’s fully-separated flare rings still remain fully separated. There will be a tiny bit of friction reduction as the ball track enters and exits the bowtie regions (where the oil rings cross), but this represents a small percentage of the ball track, and hence has a small impact. The net result is that a flare reduction from 9 inches to 8 inches is going to do almost nothing to reduce the amount of friction the ball encounters.
That explains why the plugged-hole ball didn’t hook less. But, we haven’t yet explained why it actually hooked slightly more after plugging. The answer to this was alluded to in both my last article on static imbalance ...
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