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Swing Speed and Frequency Analysis
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".
The concept of utilizing electronic calibration or "frequency analysis" to measure flex was invented by Dr. Joe Braley and his son, Kim in the 1970's. The concept is straightforward. You clamp the butt of a shaft. You oscillate the shaft. A small electric eye or laser measures the oscillations in "cycles per minute" or CPM. You translate the CPM into a relative stiffness by locating a dot on a "frequency chart".
The frequency chart is an "x-y graph" in which the vertical axis is CPM and the horizontal axis is club length. The graph becomes the "chart" or "slope chart". The slope chart will have frequency lines running diagonally from the lower left to the upper right on a 45 degree angle determined by club length and CPM coordinates. The line connecting the dots is the "slope". ** (Graphic Illustration) More on slope later.
The result is a more precise way to discuss relative stiffness. The Braley method converts CPM into a numerical value, between 2 and 8. Each "flex" is divided into "subflexes" expressed in tenths. For example, if a "regular" is determined to be 5.0 and a "stiff" is determined to be a 6.0, then a 5.5 would be halfway between regular and stiff, a "firm" in today's nomenclature.
Know Your Swingspeed
Most serious golfers today know their swingspeed with a driver and a 5 iron. If you don't, you should get measured and find out. What swingspeed doesn't tell you is how you swing. Are you a fast swinger who comes down hard or are you a smoother swinger? Do you "release" the club early or late? How you swing the club influences required shaft flex as much as how fast you swing. An experienced clubfitter can help you determine a range of choices but only after he has seen you swing. Beware of any recommendation that is based on swing speed alone.
An accomplished golfer can play well with nearly any clubs. But, finding the "perfect fit" is an artistic process that requires an experienced fitter, hitting a variety of test clubs and even playing with sample sets before you make your decision. In the end, you will make your own choice from what "feels" best and hopefully from the clubs that produce the best ball flight.
Suppress your ego. Get tested. More flexible shafts will give you more feel and might be more fun to play with. Remember that the label on the shaft is meaningless. Be prepared to choose shaft flex with an open mind. "If the shoe fits . . ."
Standard Flex Designations
As we like to say in Silicon Valley, "the problem with standards is there are no standards".
Most of the confusion relates to different techniques employed to measure CPM. When Dr. Braley invented the concept of electronic calibration measured in CPM to describe relative stiffness, he also invented a machine. It was a big, heavy clunker with a clamp on one end and a stationery electric eye on the other. The clamping length was 2 7/8 ", clubs were usually tested with the grip on, and the club was oscillated in a vertical plane, usually "toe up" to prevent banging on the machine.
Over the years, competitive equipment for measuring CPM came on the market. The manufacturers focused on cheaper, modular components and more accurate technology. The butt clamp turned into a 5" clamp, the measurement was done with the grip off to narrow irregularities caused by grip textures, and the optimum oscillation plane was horizontal, or "face down the line". These differences result in readings that can vary 10-15 CPM from the Royal Precision method. That's well over a full flex difference. Consequently, a 6.0 is not necessarily a 6.0. The actual stiffness "depends" on the variables previously described.
When you discuss CPM, it is imperative to know what method was employed to find CPM in the first place. If you want to look like you know it all, you can simply ask: "3 or 5 inch clamp" and that will put your salesman on notice that you know more about frequency than you're supposed to.
The Professional Clubmakers' Society (PCS) has devised a calibration system that gives clubmakers who are "standardized on the PCS system" the opportunity to compare "apples to apples". The PCS standard is based on a 5" clamp, grip off, and horizontal oscillation. On the PCS standard, there is still no universal agreement on what the numbers mean. However, debate has narrowed the range. Consensus is developing that "Regular" is between 4.5 and 5.0. Stiff is between 5.5 and 6.0.
Find Your Flex
What this means to you is that you should solve the equation backwards. Find a club that you hit well, get it tested. You will then know a frequency that you like for a specific club. The frequency will be a numerical value - "cycles per minute". You will then have a "dot on the chart". An experienced clubmaker can build your set of clubs based on that frequency.
However, there is one more "artistic" problem. The concept of "playing flex" implies that even if two shafts measure the same frequency, they may not "play the same" depending on other variables that relate to bend point, shaft material, temperature (no fooling!) and the psychological profile of the golfer. Your "perfect flex" will be different for different shafts. Do not expect to find a "magic number" that is good across all shafts. A "frequency that fits" is only good for the shaft type that was tested.
In the end, you will go with what "feels best". It stands to reason that making that choice requires "feeling" a variety of choices. We can't overemphasize the value of testing a variety of clubs to help you discover what feels best. On average, this is not the method employed by the professional salesmen whose goal is, once you have presented yourself qualified and ready-to-buy, wants to close the sale as quickly as possible.