Bowling-Ball Side Weight

Weight Difference Between Each Side of the Bowling Ball

The Brunswick Nexxus f(P+R) bowling ball.
The Brunswick Nexxus f(P+R) bowling ball. Image courtesy of Brunswick

If you watch or read about bowling, you may hear about side weight. Or, you may have seen a bowling ball with four holes in it and wondered why (especially since the location of the fourth hole couldn't possibly house a finger in any standard bowling grip).

What is Side Weight?

Using the finger holes as the center, imagine dividing the ball into two halves. You do this either using the right and left of the finger holes, or the top and bottom of the finger holes.

So, really, there are four halves, but actually just two different ways of measuring two halves. There is a weight difference between these two halves, and that's what we refer to as side weight.

While it might be easy to assume each half of the ball has the same weight, a number of factors make it almost never the case. The core, whether symmetrical or asymmetrical, combined with where your finger holes are drilled, almost always make one half heavier than the other, which can influence the roll of your ball.

The Importance of Side Weight

Because side weight can influence your ball so much, the United States Bowling Congress (USBC) put regulations in place to make sure nobody, essentially, can cheat. The rule states any ball weighing more than 10.01 pounds must have a difference of no more than one ounce on either side of the ball.

In any sanctioned competition, this rule must be enforced, which can require bowlers to drill weight holes into the ball to cut down on an imbalance created when a ball is drilled.

Sometimes, weight holes are drilled for strategic reasons, but that's a much more in-depth discussion on ball layouts.

If you ever bowl in a USBC-sanctioned tournament, you have to have your bowling balls weighed before you compete to confirm you're compliant. If not, the staff at the event will put a hole in your ball for you.

You don't want that, as they have a lot to do and will merely put a hole in there to make it even. You should always make sure your ball is legal after having it drilled to your specifications at your local pro shop.

Equal Side Weight Keeps Things Fair

To hint at a more in-depth discussion again, the side weight is based on the positive-axis point (PAP) and center of gravity (CG) of the ball. This is why an imbalance can create such an influence on the ball motion, and why the USBC put the rule in place to keep things even from bowler to bowler. See Drilling Your Bowling Ball: What You Need to Know First.

Drill a Weight Hole?

You can plan for a weight hole (the hole drilled to reduce the imbalance of side weight) before drilling the ball with your local pro shop, depending on a specific type of reaction you may want out of the ball. Or, if you get a ball drilled without taking into account side weight (and without measuring to confirm it's legal), you may need to add a weight hole later if you plan to enter a sanctioned competition.

You can probably get away with throwing an illegal ball in your recreational league, but don't be surprised if a tournament official wants to add an extra hole before you compete.