Learning What Flex to Use
It is not as simple as it appears to be.

"Flex" would be a relatively simple factor to fathom if club manufacturers followed a uniform set of standards. Unfortunately, they do not. Flex standards vary not only from manufacturer to manufacturer but also, from model to model within certain manufacturers' product lines.

Marketing influences often dictate whether a particular shaft is marked "XS" (extra stiff)," S" (stiff) "R" (regular), "A" (senior, or soft regular), or "L" (light, or ladies). The average male golfer should use an "R" but manufacturers know that the vast majority of them want to hit with "S". Most middle-aged males should use "A", but many have egos that demand "S". Males just feel better about themselves if they can say that they need to hit stiff shafts.

A million men have "improved" their games by switching to Callaways. They rarely want to hear that one of the primary reason for their satisfaction is the fact that their new clubs, while marked "R" are actually closer to "A".

Strength is not the key to flex selection
It is important to remember that strength is not the key determinant in deciding what flex is appropriate for any given golfer. Even clubhead speed is of secondary importance in determining what flex to use. What matters most is the golfer's tempo and the particular point in his swing where UNLOADING occurs and how forcibly he does that unloading.

Not all powerful, professional golfers use stiffer shafts. When young Jack Nicklaus was dominating the golf world with his huge, thundering drives he was using MacGregor clubs. They employed five different flexes in their shafts. Jack used the middle flex. Professional and amateur golfers unload at three basic locations during the arc which is followed by the clubhead on the way down to the ball: call them "early," "midway," and "late". Each of the three unloading positions is used with great success by various famous pros.

If your release is very late, with a rapid acceleration through the ball, then you need a stiffer flex. If your swing is smooth and rhythmic throughout its arc with no rapid acceleration at any one given stage, then you should use a softer flex.

A basic guideline for determining your flex is: "S" if your good drives are regularly over 250; "R" if the drives go 230; "A" if over 200 and "L" if they are less than 200. Always remember - there is no absolute. This guideline is not that accurate. A golfer who hits a stiff shaft for a 250 yard fade can often hit a regular flex for a 265 yard draw. Clubhead speed is not the only factor.

Another good rule is: if your drives hook, go stiffer, if your drives slice, go softer. This is appropriate since, in graphite, stiffer shafts generally have less torque (twisting of the clubhead). Softer shafts generally have added torque which twists the clubface into a more closed position at impact.

Many men actually benefit from using "A" or even "L" flex, but few will carry clubs that contain such an obviously anti-macho stigma emblazoned upon them. This is a particular problem with senior males and post-pubescent boys. Knowing that their shafts are whippy and will produce good shots only with slow smooth and rhythmic swings can force a golfer into immediate tempo changes. They will quickly learn new ways to deliver power to the ball.

Some manufacturers are wisely getting around that dilemma with new terminology. In steel shafts, "Release" shafts from True Temper are particularly popular with both seniors and juveniles. The softer, easier feel also appeals to many middle-aged players. In graphite, "Easyflex" from UST and "Turboflex" from Fenwick fill this role admirably. Top shaft maker, Aldila, uses terms such as "Smoothflex" and "Speedfit". Many premium, brand-name clubs use these shafts in their senior clubs while their regular graphites now contain what used to be standard "A" flex shafts. In addition, virtually any "ultralite" graphite will behave and feel softer than its heavier cousins. An "R" will feel like an "A".

The Psychological Factor
Another strange determinant in flex performance is the pronounced psychological factor apparent when golfers knowingly hit shafts of certain flexes. Few golfers are capable of swinging an "XS" or an "S" at anywhere close to the same tempo they use when swinging an "A" or an "L".

The average golfer has the internal belief that a stiff club must be swung harder than a softer club. Tests have demonstrated that when identical shafts have been given deceptive flex labels golfers continue to try to kill the ball with the "stiff" clubs and continue to try to "smooth it" with the "senior" clubs. They do so long after common sense would dictate that they were hitting the same shafts. Manufacturers have found that simple changes in shaft color can alter the tempo used by the hitter. Black shafts are invariably assumed to be more firm than are lighter color shafts. Silver and soft gray shafts often compel a golfer  to use a smoother, easier going tempo. This phenomenon creates the strange situation in which some given golfers need a stiffer flex in black or red shafts than they do when using softer colors. Similar is the influence created by steel versus graphite. Steel shafted irons are generally swung harder than are graphite shafted irons of the same flex.

Conclusion
    So, how does one choose what flex to use? The easiest way is to have an experienced pro or clubmaker watch you hit twenty range balls or so. The best way, however, is to hit demo clubs at a range. Ask for three 5-irons from the same product line each with a different flex. Have the salesman tape over any flex indicative markings. Then hit a large bucket of balls alternating between clubs. Keep track of your results and stick with the one which provides the best results. If it turns out to be a senior flex then buy senior flex. But, do not assume that a Callaway set will be gauged by the same standard as a Taylor or a Ping or any other set. Test the flexes of the brand you are going to buy.

Don't test for flex in one brand and then buy another. Odds are, they won't be the same. Also remember that the exact same shaft with the exact same flex will swing differently depending upon the weight of the clubhead. A heavier head from one manufacturer will make an "R" shaft flex closer to an "A". A lighter head from another will make it seem more like an "S".