Understanding your racquet, and what you can do with it
The instruments on this page are the ones we use in the workshop. They promise nothing: they measure, they calculate, and they hand you numbers. What you do with them is yours. What follows explains where those numbers come from, what they change on court, and where they stop.
The simulator: what a few grams move
Swingweight is not a weight. It is a moment of inertia: the racquet's resistance to being rotated. It is measured about an axis ten centimetres from the butt, and expressed in kg·cm². Two 310-gram racquets can read 290 and 340 in swingweight. The first is quick off the mark and gives way on heavy balls; the second drives through the ball but has to be swung earlier. Same mass. Not the same racquet.
ΔSW = m × (d − 10)² m: added mass, in kilograms d: distance from the butt, in centimetres ΔSW: change in swingweight, in kg·cm²
It is exact, not approximate, and the effect grows with the square of the distance. Take a frame at 310 grams, balance 32.0 cm, swingweight 320, and add four grams. At the tip, 66 cm from the butt: balance goes to 32.43 cm and swingweight to 332.5. Twelve and a half points more, and the racquet drives through the ball. In the handle, at 12 cm: balance drops back to 31.75 cm and swingweight does not move. Zero. At twelve centimetres you are two centimetres from the measurement axis, and two squared weighs nothing. The same four grams. A gram has no value in itself — it only has value somewhere.
The two other numbers the simulator gives you
MGR/I = ((Mass/1000) × 980.5 × Balance) / (SW + (20 × (Mass/1000) × Balance) − (Mass/10)) The ratio between the torque gravity applies to the racquet and the inertia it opposes about the butt. It describes how the racquet falls into the shot of its own accord, rather than how much you have to steer it. A value of 21 circulates as a comfort benchmark: below 20, the racquet asks to be driven.
RecoilWeight = SW − ((Mass/1000) × (Balance − 10)²) The moment of inertia about the centre of mass: what is left once the leverage effect is removed. It describes the racquet's stability at impact, independently of where you hold it. It is the number that explains why a light racquet heavily weighted at the tip can have a large swingweight and still be pushed back by a heavy ball.
The elongation curves: why the range is numbered
A string's name is a promise; a curve is a measurement. Every string in the range was tensioned on the bench in steps, with its elongation recorded at each one. That record is what orders them from N°1 to N°7 — from softest and most generous in return to stiffest and most predictable. Reading a curve teaches two things no spec sheet says: the zone where the string still responds to tension, and the plateau beyond which tightening further changes nothing in the stringbed.
What you can measure at home, and what you cannot
Mass: a kitchen scale accurate to the gram is enough. Weigh the racquet strung, grip included, exactly as you play it. Balance: lay the racquet across a thin edge and slide it until it balances. Measure from the butt to the pivot. Half a centimetre of error here shows up in every calculation that follows. Swingweight: not without a bench. The pendulum method exists and gives an order of magnitude, but its uncertainty quickly exceeds the difference you are trying to measure. Ten points are felt on court; they drown in a stopwatch reading.
Frequently asked questions
Is swingweight measured strung or unstrung?
Strung, unless stated otherwise — and it is rarely stated. A string job weighs 16 to 18 grams, spread around the head, whose centre sits at about 55 cm from the butt. By the formula, that adds some thirty points. Comparing a strung figure to an unstrung one is comparing two different racquets.
Are ten points of swingweight noticeable?
Yes. The commonly quoted perception threshold is around 3 %, that is about ten points on a racquet at 320. It is also the order of magnitude of the gap between two units of the same model out of the factory — which is why you can love your racquet and dislike the same one bought a year later.
Can swingweight be lowered?
With difficulty, and never by adding anything. You would have to remove material where it counts, that is at the tip — which a frame does not allow. The only clean lever is the string: a thinner gauge and a lower linear mass take off a few points without touching the frame.