Swing Speed and Frequency Analysis

Fitting Flex by Swingspeed
For many years, fitting flex in golf clubs has been accomplished by estimating or measuring swingspeed and then choosing a shaft and head design according to the perception, knowledge and experience of the fitter. Lately, fitting by swingspeed has turned largely psychological and is driven by marketing requirements of the major manufacturers.

Any ambitious, good golfer with dreams about playing near a professional level wouldn't be caught dead with anything but an "X" or "Tour Stiff". Pretty good amateurs are going to go for "S" or better. Only beginners and low self-esteem golfers choose "R".

The major manufacturers have figured out that most golfers can't hit a truly stiff shaft so they compromised by putting "S" or "Firm" labels on much softer shafts. This was a primary reason for Callaway's surge in the early 90's. They sold their customers nice, easy to hit "R" or softer shafts in their Warbirds and Berthas, they just labeled them to fit the golfer's self image. The integrity of shaft labels was destroyed.

As a consequence, it is impossible today to know what flex a shaft is by reading the label. This is especially true with graphite. The golf industry has responded with a more precise technique to measure shaft flex now known as "frequency analysis".