As a new tennis player I am literally scared of “new balls”. My observation was that I played badly and invariably lost with new balls. In particular I usually hit new balls way out of the court; and further I seem to be struggling more than anyone else!

If I think about it in detail, for me new balls had the following annoying characteristics:

They bounce too high, over shoulder high

They hit out way too easy (too flighty)

They make the opponents serve too fast

They feel like bullets not tennis balls!

So what is going on? Why are new balls hard to deal with for beginners? It is not because they break the rules, in fact the rules are fairly tight, namely:

Mass should be: 56–59.4 gm

Size should be: 2.575–2.700 inches (6.541–6.858 cm)

Bounce should be: 53–58 inches (135–147 cm) from 2m drop

Forward deformation should be: 0.220–0.290 inches (0.559–0.737 cm)

Maybe it is not just me because at the 2022 US Open, Iga Swiatek and other pros criticized the tournament organizers for using lighter tennis balls for womens and heavy ones for men. in 2023 Daniil Medvedev and Stan Wawrinka expressed concern about the Dunlop balls used at the Australian Open and other ATP hard court events, saying they are responsible for an increase in injuries to elite players.

Ball Construction

The tennis ball is two rubber hemispheres and covered with two pieces of woven “melton” wool and nylon cloth. The rubber was “indian rubber” formed from a vulcanisation invented by Charles Goodyear. Recently, needle cloth has been used as a covering ( more nylon fibers in the felt and construction is done by “needle-punch” instead of the woven used on the premium balls), which is less durable and cheaper to produce. Internal pressure is about 12 psi above atmospheric pressure. Long life balls have LongPlay felt but can get very fuzzy and some have additives like Slazenger’s Wimbledon which uses Hydroguard technology to repel water.

Are New Balls Too Heavy?

Well, yes they can be. New balls can be +/- 1g over published weight thats typically between 55g to 60g out of the box…..not much of a difference? Think again. From physics force equals change in momentum (mass x velocity) with time 33.5 m/s x 2 (rebound) / 0.05.

So to return a 75mph tennis ball of 55g, force required is = 76 newtons. In fact the force on the racket from a 55g ball at 81mph is the same as a 59g ball at 75mph.

When you also consider balls get heavier when wet, then a wet ball might be 69g, then a 75mph balls hits with 93N almost the same as a 100mph shot from 55g! And new balls also lose mass, literally by felt and fuzz flying off…..you actually see it all over the court.

Are New Balls Too Bouncy?

New balls will bounce up 70% of their drop height, which is pretty impressive. But when hit hard they struggle to rebound as efficiently and return about 50% of its pre‐impact energy (strings are much more efficient, returning 90–95% energy). New balls do become less bouncy fairly quickly, mainly because they loose their internal high pressure.

Another factor is that modern balls are harder than before. They are being made with more solid rubber internal structure, as shown below in the forward deformation. They stay on the strings less time overall.

Are New Balls Too Flighty?

Yes. IMO brand new balls are very flighty….meaning the aero drag is low. Thats because they begin very smooth. As they fluff or fuzz up they gain a lot more drag in the air , hence more friction with ground and strings. So basically new balls become slower and grippier (more controllable) even within 1 game sometimes.

Their aero drag has been studied in the lab and looks like this.

Is it the Same for the Pros?

Yes and No. Pros have new balls in practice and every 7 games. So they only have “brand new balls”, and “almost new balls”. However there is definately an effect. Stephanie Kovalchik data analyst found ball freshness (time since new balls were changed) correlated with win rate for aces > serves > ground strokes for Pros in ATP and WTP (but especially the WTP) with the effect favoring stronger players.

What this deep dive into tennis ball science shows is that the “new ball” effect is real and favours better players. The better the player, the better they will handle new balls and leverage them to their advantage. So by implication, old balls therefore must favour worse players. Or at least old balls make it hard for better players to squeeze out an advantage.

Oh Dam. I just found out the hard way that I must be a “worse player” !

Citations

http://on-the-t.com/2016/07/08/klaassen-magnus-hypothesis-18/