Compression is a number describing how far a ball deforms under a defined load. A soft ball sits around 50 to 60, a tour ball at 85 to 100. What that means on the course is not printed on the box, and most shop assistants explain it badly.
At impact the ball is on the face for roughly half a millisecond. In that time it has to compress and spring back — and it is that return to shape which fires it forward. If the ball is not compressed enough, some energy never becomes ball speed and is instead lost in the deformation of face and shaft.
Numbers help. A 110 mph swing compresses a Pro V1x (97 compression) essentially fully. A 78 mph swing compresses the same ball barely halfway and gives up somewhere around three to five metres of carry against a 60-compression ball. Hardly a catastrophe, but it is a pointless loss at twice the price.
Then there is feel. A firmer ball sounds sharper off the putter and players describe it as "quick". That is not subjective nonsense — it is measurable, since compression directly affects how fast the ball leaves the face for a given stroke length. Which is why we always suggest a practice-green session before taking a new ball into a competition.
Temperature shifts things more than people expect. At 8 °C a ball behaves several compression points firmer than at 25 °C, so you lose carry in November without changing anything at all. Going softer for winter — a Srixon Soft Feel at 60, for instance — and back to a tour ball in summer is a genuinely sensible plan.
The simple rule we use in fittings: driver speed under 85 mph means compression up to 70. Between 85 and 100 mph, look at 70 to 90. Above 100 mph, 90 and upward is fair game. It is not law, but as a starting point it holds nine times out of ten.
One last thing. If you are losing more than three balls a round, this entire discussion is academic. Buy a dozen cheap two-piece balls, go and play, and revisit the tour category when you stop donating balls to the trees. You will save a few hundred euros a year and your scores will not notice.
