Some balls are indicated with a compression of 80, 90 or 100 etc. Originally it was used as a measurement for quality of 3-piece balls, where a long rubber was stretched around the core. The rubber had a length of approx. 20 meters and was stretched at a factor of approx. 20 times of its original, depending on the compression that is wanted. This way it is wounded around the core. It was said that the tighter the windings, the better the ball performed. This created a long-standing perception that compression affects golf ball distance and performance.
Because golf ball technology uses newer heat-resistant threads with newer and better winding equipment for three piece balls, golf ball compression has become merely a condition of feel. Now with the availability of the consistent quality of a two piece ball, compression as a measurement of quality is rather obsolete.
Definition: Today the word “compression” in the golf ball industry relates to a value expressed by a number in the range from 0 to 200 that is given a golf ball. This number defines the deflection that a golf ball undergoes when subjected to a compressive load. Compression simply measures how much the shape a golf ball changes under a constant weight.
Measurement: All three-piece balls and some two-piece balls are measured for compression. A ball that doesn’t compress is rated 200; a ball that deflects 2/10ths of an inch or more is rated zero. Between those two extremes, for every 1/1000ths of an inch that the ball compresses, it drops one point from 200 and the compression rating is then established.
Most balls have compression ratings of either 80, 90, or 100; the lower the compression, the softer the feel. Not every ball marked 80, 90, or 100 is exactly that rating. The actual rating can fall roughly within 3-5 points on either side of the indication. Any ball that falls out of this range is usually sold as range ball, or as X-outs.
Prove: There have been several published texts to prove that golf ball compression relates more to feel and your own superstition than its performance. The conclusions were, if you take different rated golf balls which have the same construction, aerodynamics, and cover material, and use an automatic golf swing machine such as the Iron Man, the yardage difference between the balls hit were negligible, less than two yards.