Golf shaft flex is typically defined by shaft manufacturers by a scale consisting of the designations of L, A, R, S, X.

In this scale, L is the most flexible and X is the stiffest.  The simple “rule of thumb” that the faster your swing speed the stiffer a shaft you need… is mostly a marketing game played by the manufacturers.  30 years ago this might have been true, but today there are too many variables among the shaft offerings.  For example… Manufacturer A’s shaft labeled as S for stiff, might be more flexible than Manufacturer B’s shaft labeled R for Regular.  I see this all the time… so I encourage players to ignore shaft labels. 

Most good club fitters know to ignore the label and test a shaft flex by using cycles per minute (CPM).  To get CPM, a shaft is clamped to a special tabletop device, weight added to the tip end,  the weight is sprung and measured for the number of cycles per minute it moves back and forth.

So why should you care about CPM?  Isn’t “close enough” OK?

We’ll explore that in the next post…


Al Humphrey

Professional Club Fitter
Master Club Builder