Technical Tips

November 2011

A Technical Discussion of Shaft Swing Speed Ratings
From: A Publication of Tom Wishon Golf Technology • March 2011
by Tom Wishon

Most clubmakers are well aware that the letter codes used by the golf equipment industry to designate the flex of shafts are virtually meaningless. Because standards have never been established in the industry for flex, the familiar letter codes of L, A, R, S and X used to convey the flex of a shaft have little bearing on how stiff or how flexible a shaft really is. Not only can it be said that the R-flex of one company can be equivalent to the S or A-flex of another company, but very often shafts of the same letter flex from a company are manufactured to vary by one or more flexes in actual stiffness.

Such inadequacies have made it difficult to fit a golfer with a shaft stiffness design that matches their swing ability to develop proper bending of the shaft during the swing. Golfers who choose the shafts for their clubs by using a letter flex code are quite literally simply guessing to the point if they do end up with a suitable flex for their swing, the result was pure luck.

In his 1991 book, The Modern Guide to Shaft Fitting, TWGT's Tom Wishon developed the golf industry's first methodology to award a swing speed rating for shafts. While this first methodology for determining a swing speed rating for shafts was quite elementary, it served as the beginning of an ongoing process for ever improving the means by which empirical measurements of shaft stiffness could be translated into a swing speed rating to then serve as a beginning process for fitting golfers.

The theory behind using a form of relative stiffness measurements of a shaft and translating that into a swing speed rating is based on the assumption that as a golfer's swing speed increases, so too does the overall, average amount of bending force put on the shaft. However, there is no question that two golfers with the same swing speed do not always generate the same amount of actual bending force on a shaft. This is why TWGT's shaft fitting methodology as taught in our Common Sense Clubfitting book and outlined briefly on pages 62-63 of our 2011 catalog teaches that an evaluation of the golfer's transition and downswing tempo must then be referenced to the golfer's actual swing speed to be able to know what final shaft swing speed rating is best for each golfer.

Which leads us to today, some 20 years after the first methods for trying to award a swing speed rating to shafts began. In determining the swing speed rating for any shaft, TWGT now uses the 41", 36", 31", 26" measurements and with additional input from the 21" measurement from its bend Profile Software methodology to come up with each shaft's swing speed rating. This is why the 21" measurement column in the table below is highlighted in green. We feel the swing speed rating for a shaft has to relate to the stiffness design of the upper 2/3's of the shaft. We do not use the tip section stiffness measurements in the determination of a shaft's swing speed rating. However, in some cases we will look at the 21" measurements if the shaft's swing speed rating may be in between two speed levels to help us make a final determination. We believe the tip end of the shaft is related to the golfer's release point on the downswing and is therefore not a part of a shaft's swing speed rating.

At present we believe the swing speed rating of a shaft should be based on the 41" to 21" measurements because it is this part of the shaft that is more susceptible to bending from the golfer's swing speed plus their downswing transition force and downswing tempo/acceleration into the ball. It is this part of the shaft that we believe in our current work comprises what the rest of the industry calls the "flex" of a shaft, from a basic flex fitting standpoint.

In addition, over years of analyzing the bend profile measurements of more than 1500 different shafts, through statistical analysis of the 41" to 21" measurements compared to actual fitting experience with many golfers, we have created a table of shaft measurements which we have set up to correspond to basic shaft swing speed ratings. Below is the table based on our current work that we use to award swing speed ratings for WOOD shafts. Please understand that as we continue to design, measure and analyze shafts in addition to continuing to fit and analyze golfers, we consider this to be an ongoing "work in progress".


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