The weather restrings your racket for you

Temperature and humidity move effective string tension by more than most of the adjustments players agonise over.

A player asks for two kilos less than yesterday because the ball felt like it was flying. Reasonable request. There is a decent chance the stringer could have left the machine alone and the conditions would have done the job.

Polyester loses tension fast. It drops measurably within the first hour after stringing, keeps dropping, and by the second day a bed strung at a given number is playing several kilos lower than the label says. Layer temperature on top: warm strings are looser and livelier, cold strings are stiffer and duller, and the ball itself is bouncier in heat and heavier in damp air. A night session after a hot afternoon is a genuinely different racket in your hand, and nothing about it was your stringing.

So the tension a player names is not really a physical setting. It is a target feel, and the stringer's job is to hit that feel under today's conditions, which is why good tour stringers ask what the forecast is before they ask for a number.

The mistake I see at club level is treating the number as identity. People will tell you their tension the way they tell you their shoe size, and then play the whole season on a bed that died in April, adjusting their swing to compensate without noticing. That compensation is where arm injuries come from. A dead polyester bed is stiffer, transmits more shock, and produces less spin, so the player swings harder to get the shape back, on a string that is now punishing them for it.

The honest guidance is dull and correct. Cut them out on a schedule based on hours played, not on breakage. If you play twice a week, restring roughly twice a year is nonsense; the string is finished long before it snaps.

There is a further point that annoys equipment purists and is nonetheless true. The difference between two kilos of tension is smaller than the difference between a fresh bed and a three-week-old one, and far smaller than the difference between a new ball and a fluffed one.

Which means most of the tension conversation in tennis is people making a small adjustment very precisely while a much larger variable moves around underneath them, unmeasured, all season.