Behind The Bounce: The Mechanical Properties of Your Tennis Ball

Tennis players of all levels know that the right ball can make or break your game. But how do different balls compare, and how can manufacturers reliably measure these differences?

All tennis balls are made of a felt outside, rubber core, and hollow inside filled with pressurized gas or air. These seemingly simple components create different balls with variable bounce, trajectory, and flight in game.

Players often prefer certain brands or models, like championship or tour. But are those preferences rooted in real performance differences, or just habit and hype? Science says yes: measurable differences do exist.

Most manufacturers test tennis balls with drop weights and air cannons, but these methods are not as precise or repeatable as mechanical analysis lab equipment. To illustrate the benefits of mechanical analysis, we tested tennis balls on different brands to assess their stiffness and response to being hit.

We tested four different tennis balls with these specifications given from the manufacturers and general industry preferences:

• Championship Ball 1: A popular ball with normal wear and durability, designed for consistent performance in hard-court games
• Championship Ball 2: A different brand’s reliable and durable championship ball, similarly designed for hard-court games
• Extra Durable Ball 1: High-performance ball designed for extended durability and longevity with less wear. From the same manufacturer as Championship Ball 1.
• Youth Ball: Designed for advanced beginner youth players, around 9 to 10 years old

A defining mechanical property of a tennis ball is stiffness: the amount of force it takes to compress it (force/deformation = stiffness). We measured stiffness by compressing the tennis balls between two plates (platens) at a relatively low speed. The deformation and the resulting force were measured. The compression stiffness is going to be highly related to how hard/fast the ball bounces off the racket or ground.

As expected, the youth ball has the lowest stiffness. Its extra give makes it easier to hit with less force, perfect for child players.

The adult tennis balls had relatively similar stiffnesses to each other. Interestingly, the two championship balls were more different from each other than they were from the extra durable ball 1. Championship 1 and extra durable 1 are from the same manufacturer, so despite being marketed as different products, they were still more similar in stiffness than another brand’s championship ball. So, if you’ve ever switched from one brand’s championship ball to another and noticed a difference in bounce and play, you may have been sensing a measurable difference in stiffness.

The tennis balls were also very resistant to degradation, with 1,000 cycles of compression only causing a 1% change in properties. Tennis balls are therefore very durable, and not likely to change their properties over the course of only a few games.

Next, we tested three of the same kind of ball from the same tube to assess variability among the “same” tennis ball. We compression tested three balls from the same tube for both championship ball 1 and championship ball 2, with results shown below:

Our compression testing of tennis balls revealed interesting differences, including brand-to-brand variation on the same kind of tennis ball and divergent properties among balls from the same tube.

Another interesting tennis ball property to be explored is their rubber core’s viscoelasticity, meaning they exhibit both viscous (liquid-like) and elastic (solid-like) properties. Their mechanical behavior is therefore strain rate-dependent. For example, a tennis ball undergoing the same amount of force will respond differently when that force comes from a hard-hitting smash versus from slowly being stepped on. Future work could quantify differences in viscoelasticity using Dynamic Mechanical Analysis (DMA).

From stiffness and bounce to durability, the ElectroForce Apex 1 was the ideal doubles partner for tennis ball analysis in the lab. The Apex 1’s high accuracy force and displacement sensors far exceeds industry calibration standards, detecting subtle material differences with remarkable reliability. Built for efficiency and flexibility, the Apex 1 facilitates monotonic, fatigue, and DMA tests with easier user training than perfecting your tennis serve. From tennis balls and tires to medical devices and more, the Apex 1 instrument is your partner in material innovation.