Sport Science: The Lowdown On The Roland Garros Clay

Matthias Hauer/GEPA/USA TODAY Sports

From player sliding to balls springing, clay leaves its mark on a match in many different ways.

Sure, you already knew that the balls are bouncier at the French Open. And that points last longer. But do you know why? Read on for a by-the-numbers look at the clay of Roland Garros.


1.1 tons: The total amount of red clay -- in fact, crushed brick -- used to top the surface of a court at Roland Garros. The courts are actually layered like a cake, with the main surface being a 4-inch thick layer of limestone. The signature topcoat of red clay is less than 0.08 inches thick.

0.85: The coefficient of restitution of a clay court, which is the measure of a surface's elasticity. For comparison, a grass court will have a lower coefficient of restitution, around 0.75. In other words, clay is much "bouncier."

40 percent: The approximate speed lost when a ball without spin collides with a clay surface. To put that in perspective, a ball bounces off a grass court about 15 to 20 percent faster, thanks to lower friction.

50 milliseconds: The average extra amount of time players have to hit a 120 mph serve when playing on clay versus grass. That may not sound like much, but it gives players an additional 20 percent of decision-making time.

7 degrees: On a 120 mph serve, with all else being equal, this is the angular increase in a ball's bounce trajectory from impacting a clay surface over grass.

20 to 30 percent: The percentage of an entire match actually spent playing when on a clay court. That's roughly double the effective playing time on a fast court.

150 beats per minute: Approximate mean heart rate of an athlete playing tennis on a clay court -- nearly 10 percent higher than it is when playing on a hard court.

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