Bowling Layouts

Bowling balls and static weights – Part II

Having defined how the static weights are determined in Part I, it’s now time to move forward and determine what they reportedly do and where the points of contention come in.

Static Imbalance and Ball motion

Until 10 short years ago, perhaps even more recent than that, the only tools we had to gauge ball motion were our eyes. There was no extensive ball motion study and no one had done anything more than casual, unscientific observations of balls on the lane after they were drilled. It was quickly figured out that the pin to PAP distance played a significant role. It was also discovered that the height of the pin, relative to the finger holes, seemed to play a role in how strong the ball was on the back end. The purported cause at that time was that the way mass was being removed from the core of the ball was a large factor in how the ball reacted on the lanes. As a result, the following observations were made:

  • Balls with positive side weight seemed to roll sooner than balls with negative side weight.
  • Balls with thumb weight seemed to roll sooner than balls with finger weight.
  • Balls with bottom weight tended to cause a loping effect, which tended to make the ball roll a little later.
Bowling ball balance scales
Kaufmann "Dodo" Scales. Image courtesy of Innovative Bowling.

Now, the only way one could accurately gauge the final static imbalance was by using a Kaufmann “Dodo” Scale to find the static imbalances on the ball. Eventually, a layout system that put the pin and CG at specific distances from the PAP was invented as a means of predicting how the ball will react on the lane. This layout system would accurately position the CG and Pin to give the ball the desired ending static weights when drilled.

The Advent Asymmetric Cores and the Mass Bias

This system seemed to work for quite a few years. That is, until the late 90’s, when Hammer released a ball called the 3D offset. This ball was the first to have a KNOWN Mass Bias, a term coined by ball designer Mo Pinel (yep! that guy again!) due to the shift of some of the cores weight toward one side of the ball, thus having the mass biased to one half of the ball. Thus, asymmetric cored bowling balls were created and this Mass Bias is what we now call the Preferred Spin Axis, or PSA. It was quickly observed that asymmetric cores tended to be much stronger down lane, creating a more angular motion at the break point. It was also observed that the CG location started to play a tertiary role to the Pin and PSA. This meant that the traditional layout system of measuring out the distance of the CG and Pin from the PAP didn’t work for asymmetric balls, so the system was adapted to include measurements from the Pin and PSA relative to the PAP.

Computer Modelling and CG-No-Matter

Sometime in 2005, in response to a proposed rule change from the USBC that would require all balls used in competition to have the CG within 1″ of the grip center, the Brunswick R&D Group release a video (shown below) showing that even with the CG in dramatically different places on the ball and dramatic differences in side weight (2.125oz positive vs 0.675oz negative), for symmetric cores at least, the difference in reaction was negligible at best. This video included a CAD animation, showing how the core position changes when all but the CG position is held constant. The animation shows us that the orientation of the core does not change in any significant manner at all. In fact, it could almost be said that the core doesn’t really change orientation! Track flare and resulting ball reaction back up what is later asserted – CG position does not play a significant role in final ball motion. Thus started the “CG No Matter” school of thought and along with it, the raging debate – Do static weights play any significant role in ball motion.

USBC Studies

In 2008, the USBC released it’s findings in the ground breaking Ball Motion Study. In the study, the research compiles a list of 18 weighted variables. The top 5 variables all related to the surface and friction that was able to be created between the ball and the lane. Four of the next six variables related to the mass properties of the ball (RG, Total Differential, Spin time and Intermediate Differential), with only ONE of the static weight imbalances appearing in the same list: Side weight. In the end, side weight, top weight and thumb weight came in 11th, 15th and 17th respectively, in order of importance when it comes to final ball motion. These results imply that static weight imbalances are much less significant in the resulting ball motion than mass properties are. This is in line with the findings and teachings of Brunswick and Morich and is in fact what is currently being taught at IBPSIA HOTS and Advanced Certification classes.

In 2011, in response to intense scrutiny from the greater bowling community, including some ball manufacturers and pro shop operators, the USBC released the results to the first part of its Static Weights Study. The purpose of this study was intended to finally put the debate to rest. However, it raised more questions than it answered as the majority of the data presented dealt with the more extreme measurements of static weight imbalances.

The example that seemed to be the golden child for the relevance of static weight limits was a ball that had 5.875oz bottom, 3.75oz positive side weight and 3.75oz finger weight rolled at 14mph with a rev rate of 600rpm. This ball presented a 4th phase of ball motion, causing the ball to hook back to the right after it had completed it’s roll phase. If we examine that ball, all of the static imbalances are almost twice the current limit for top/bottom weight (currently 3oz) and almost four times the current limit for finger/thumb and side weight (currently 1oz respectively). What’s more, the bowler specifications of 600rpm at 14mph is HIGHLY unrealistic! Most bowlers that I’ve met and dealt with have somewhere in the vicinity of 200rpm-350rpm and ball speeds of 15mph-20mph, so the experimental bowler lies WAY outside the averages. I think professional bowlers Jason Belmonte (Two hands), Osku Palermaa (Two hands) and Robert Smith are the closest to the rev rates (500+rpm), but the all possess extremely high ball speeds as well (19+mph), so again, the fall WAY outside the extreme case used to push the point. I believe Tom Smallwood is the only current professional who comes close that kind of speed/revs combination at around 450rpm and something like 16-18mph, so, still not even in the ball park on either statistic.

That leaves us with the lingering question – how relevant are static weight imbalances to final ball motion? If the weights and bowler specifications had been more sane values, pushing only one variable at a time, rather than five all at once, a more meaningful conclusion could have been drawn. It is very possible that tests were run with more those tests were run, but the results are not presented to the reader in any complete form, but rather as anecdotal examples of what COULD happen, should a pro shop operator decide to go rogue and deliberately drill a ball WAY out of specifications.

So, where does that leave us?

At this point in time, we are no closer to completely settling the debate. The general consensus is that with the current limits, static weights have minimal influence over the final ball motion, with some experts quoting total influence at less than 1%. However, since the current USBC study only shows that there are possibilities of the extreme imbalances causing unwanted motions that might in fact help bowlers score, for the moment at least, we are stuck with the limits we currently have – 3oz top/bottom weight, 1oz finger/thumb and side weight. I would propose that if the lifted the limits on finger/thumb and side weight just 0.5oz, to 1.5oz a piece, this would create a much wider market for balls that come with short pin distances (Pin to CG measurements of 2″ or less) and Pro-pin (Pins outs of 5″ or more)  and Pro-CG balls (top weights well of 3.5oz or more and CG’s 1″ or more out of line with the Pin-to-Spin line).

Currently, these balls are difficult to sell and even more difficult to drill for most customers because they limit layout possibilities. This would relieve inventory pressure for both the distributor and the pro shop (most bowlers look for balls with 2″-4″ pin out and 2oz-3oz top weight) and it would reduce the risk for the bowler when buying from online vendors, which tend to ship very short pins and high top weights if the bowler doesn’t specify what top weights and pin outs they want. Everybody wins!


By now, it should be clear that I am firmly in the “CG No Matter” camp. From my own personal experiences, I’m pretty darn certain that static weights offer very little value to ball motion what so ever. At least at the current limits. I hope that this article, and it’s companion, Part I, offer a little more insight into what static weight imbalances and what role they play, if any, in final ball motion.

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