"Flex" refers to the ability of a golf shaft to bend as forces are applied to it during the golf swing.
Those forces are generated by the type of swing that you have - fast or slow, smooth or jerky.
There are five generally used ratings for shaft flex: Extra Stiff, Stiff, Regular, Senior and Ladies, usually denoted by the letters X, S, R, A and L ("A" is used for Senior because this flex was originally called "amateur").
Having a flex that doesn't match the needs of your swing will result in the clubface being misaligned at impact, causing your shots to go off-target.
What Flex Impacts
Shaft flex impacts, either directly or indirectly, the accuracy, trajectory and distance of your shot. Three pretty important things, eh?
As the shaft flexes throughout the swing, the position of the clubhead changes. And the face of the club must be square (perfectly straight) at impact to get the most out of the shot. If you have the wrong flex for your swing, there is less chance that you'll make contact with the ball with a square clubface.
Some General Guidelines
The degree of flex in your club shafts is something you control. You can choose to buy stiffer shafts, or softer shafts, depending on your needs.
But how can you tell what you need? Here are some general guidelines:
• Take a look at the distance you hit your driver. This is a good, but very general, indicator. If you carry you driver 250 yards or more, go with Stiff; 230-250 yards, Regular; 200-230 yards, Senior; less than 200 yards, Ladies. Only the biggest of the big hitters is going to need Extra Stiff. For most of us, Extra Stiff isn't even in the picture.
• If you have a very smooth swing, you might benefit from a softer flex even if you swing fast. A swing that gets jerky at the top - when transitioning into the downswing - will probably need a stiffer shaft.
• If your drives go left, you might benefit from a stiffer flex; if your drives go right, you might benefit from a softer flex.
If Your Flex Is Too Stiff
What effect does a too-stiff shaft have on your golf game?
1. The ball will probably fly lower and shorter for any given loft, compared to a properly fit shaft.
2. The ball may tend to go to the right, or fade side, for right-handed golfers because with a too-stiff shaft the clubface is harder to square (the clubface is more likely to be open at impact, in other words).
3. The shot may feel less solid, more like a mis-hit even if you make contact on the center of the clubface.
If Your Flex Isn't Stiff Enough
And what will happen if your flex isn't stiff enough?
1. The ball might fly higher for any given loft, compared to a properly fit shaft.
3. Shots may tend to feel more solid, even when they aren't.
Macho, Macho Men
Men like to hit Stiff shafts. It's a guy thing. Unfortunately, it's not always the smart thing.
No macho man wants to be seen hitting a wimpy little Regular flex club, or, Tiger Woods forbid, a Senior or Ladies flex.
But overswinging is a common problem among male high-handicappers. Choosing a softer flex often has the effect of forcing macho men to slow down their swings. And slowing down the swing often makes those macho men into better players.
And the fact is, the harm in hitting a shaft that is too flexible is much less than the harm in hitting a shaft that is too stiff. As equipment guru Tom Wishon has said, when unsure about flex, always err on the side of more flex (meaning, a softer shaft). If you can't decide between Regular and Stiff, go with Regular.
The Foolproof Way to Choose Flex
A clubfitting with a golf professional is the recommended way to choose the proper flex.
The pro will take a lot of measurements, watch your swing, measure your swing speed, watch your ball flight and be able to recommend the flex that is right for you.
Clubfittings are available at many pro shops and almost all golf schools and from teaching professionals.
If a club-fitting isn't in your future, the next best thing is a demo day. At demo days, you'll be able to hit many different types of clubs with different types of shafts.
The key, short of a club fitting, is hitting lots of different clubs and watching the effect that changing shaft flex has on your shots.
If you find a flex that feels good and produces a good ball flight, there's a good chance that's the right flex for you.
Golf Shafts FAQs
• How do steel and graphite shafts compare?
• What makes finding the right flex so important?
• What are the elements that go into choosing the correct shaft flex?
• Are there industry-wide standards for shaft flex?
For much more about golf shafts, see Tom Wishon's Golf Shafts FAQ, from which some information for this article was taken.