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Shaft Reference

A Flex Letter Is a Marketing Decision, Not a Measurement

There is no standards body behind the letter printed on your shaft. This page explains what can actually be measured, and what we measure before recommending anything.

Start here

The Letter Problem

Two shafts, both stamped S, can differ by a wider margin than the gap between one maker's R and their own X. Nobody is being dishonest. There simply is no shared definition of what S means, so each manufacturer sets it against their own internal reference and their own idea of the customer they are selling to.

This matters because players carry the letter around as though it were an identity. Someone who has played S for twenty years will resist an R even when the measured behaviour of that particular R is stiffer than the S they arrived with. The letter is doing real damage to a decision it was never qualified to make.

On the bench, the letter is recorded and then ignored. What gets used is the measurement.

What We Actually Put on the Sheet

Four figures, all taken here rather than copied from a catalogue, because installed behaviour and specification-sheet behaviour are not reliably the same thing.

  • Raw and finished mass. What the shaft weighs before trimming and what remains after it is cut to your length.
  • Butt frequency. A cycles-per-minute reading of the assembled club, which is a real number that can be compared across the set.
  • Section behaviour. Where the shaft gives way along its length, taken at three points rather than described with an adjective.
  • Torque. Recorded when the maker publishes it, treated with caution because measurement methods differ between makers.

Four numbers will not tell you everything about a shaft. They will tell you enough to stop arguing about letters, which is most of the battle.

Letters on the rack
Recorded, then set aside
Frequency
Measured assembled
Profile points
Three per shaft
Trim charts
Starting points only

The One Sentence Version

Get the mass right first, the bend behaviour second, and treat the letter as packaging. Most players who feel a shaft is wrong are reacting to its weight long before they react to its stiffness.

Bring the Shaft You Already Like

If one club in your bag feels better than the rest, bring it. We will measure it and use it as the reference the rest of the set gets built toward. That is far more useful than any preference expressed in words.

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Mass

Weight Is the Variable Players Feel First

Change a shaft's mass by fifteen grams and almost everyone notices. Change its stiffness by an equivalent amount and most people do not. Weight is where a fitting should start.

Rough bands we work within, before any individual measurement
Where in the bag Common range What moving lighter tends to do What moving heavier tends to do
Driver and fairway 45 to 85 g More speed, wider spread, a livelier head through impact Tighter pattern, calmer transition, some speed given up
Hybrid 65 to 95 g Higher launch, easier from poor lies Flatter flight, better matched to an iron set
Iron, graphite 55 to 105 g Kinder on hands and joints, more speed retained Steadier strike location across the face
Iron, steel 95 to 130 g Slightly more speed, more feedback through the grip Traditional feel, tighter groupings for stronger players
Wedge 105 to 135 g Rarely helpful; wedges reward mass Better turf feel and control on partial shots

These bands describe where products sit, not where you should sit. Two players with identical swing speeds regularly land forty grams apart because one transitions gently and one does not. Speed is a poor predictor of shaft mass, which is why we do not fit from a speed chart.

Torque, Briefly

Torque describes how much a shaft twists under load. Lower figures are marketed as more controlled, and for very strong players that is broadly true.

The caution is that makers measure torque differently, so a 3.2 from one company and a 3.2 from another are not directly comparable. We record the published figure and give it far less weight in a decision than mass or bend behaviour.

If someone sells you a shaft primarily on its torque number, ask how it was measured. The answer is usually vague.

Tip Trimming Changes the Shaft

Cutting material from the tip end stiffens the lower section, sometimes dramatically. The same raw shaft can finish noticeably firmer or softer depending on how it was prepared, which means a shaft model is not really a fixed object until it is built.

Manufacturer trim charts are treated here as a place to begin. The assembled club gets measured afterwards, and if the reading disagrees with the chart, the reading wins.

Bend behaviour

Where the Shaft Gives Way Matters More Than How Much

Two shafts can arrive at the same overall stiffness by entirely different routes. One might be soft in the middle and firm at the tip; the other the reverse. They will not launch the ball the same way, and no single letter or single frequency reading distinguishes them.

This is why we take readings at three points along the shaft rather than one. The pattern across those three points is what actually predicts whether a player will see the flight rise, flatten or stay put.

The Shorthand, and Its Limits

The trade talks about tip-soft and tip-firm profiles as though they were categories. They are useful shorthand and they are also a compression of something continuous. A shaft described as tip-firm by its maker can measure closer to the middle of the field once it is cut for a shorter player.

What survives contact with the bench is the measurement of the finished club, in your length, with your head mass, and your grip on it. That is the only version of the shaft you will ever actually swing.

Consistency Across the Set

For an iron set, the useful thing is not any single reading but the progression of them from long iron to wedge. A set whose readings step evenly tends to feel like one instrument. A set whose readings jump about tends to produce a player who trusts three clubs and hopes with the rest, usually without knowing why.

Uneven progression is one of the more common findings on a first visit, and it is frequently fixable at the bench without buying anything.

Desert notes

Two Things This Climate Does to Shafts

Heat

Epoxy joints and a car boot in August

A closed vehicle parked in Palm Springs in July reaches temperatures that a properly cured epoxy joint will survive but an indifferently cured one will not. We see a handful of loose heads every summer, almost always on clubs assembled quickly somewhere with a same-day promise. Cure time is not a corner worth cutting in this valley, and ours are left overnight as a matter of routine.

Dryness

Grips age faster than the calendar suggests

Single-digit humidity for months at a stretch hardens rubber compounds noticeably quicker than the same grip would age in a damp climate. A grip that would comfortably last a season elsewhere often needs replacing here after fewer rounds. Since grip mass affects the balance of the whole club, a hardened, worn set is quietly a specification problem as well as a comfort one.

Neither of these is a reason to buy anything. They are reasons to have the set looked at once a year, which costs very little and occasionally saves a head.

What is on the rack

Measured beats described, every time

Bring the club that feels right and the club that feels wrong. An hour on the bench will usually explain the difference in numbers.