In the first edition of Shafts 101, we explored shaft flex. Today, we’re looking at torque. Though it’s not as talked about, torque is every bit as important as flex when it comes to feel and performance.
What is Torque?
Once again, we’ve brought together the top shaft manufacturers to discuss our topic. Interestingly, though they had varied definitions for shaft flex, their definitions of torque were very similar.
Torque is the measurement of a shaft’s resistance to rotational twisting. Torque is expressed in degrees – the higher the number, the less resistance.
How is Torque Measured?
If you read the first Shafts 101, you know that there are virtually no industry standards in shafts. Measuring torque is no exception.
While the specifics may vary, the procedure for measuring torque is the same across the point. The butt of the shaft is clamped, a force is applied to the tip, and the degrees of twisting are measured. What can vary are the size of the clamp, the distance between the clamp and the force, and the amount of force used.
Torque = Feel
One of themes that came up frequently was the connection between torque and feel.
When a shaft has higher torque (is more able to twist), it will feel smoother and softer. Lower torque shafts feel stiffer. What many players describe as a shaft feeling too soft or too stiff may not be related to flex as much as it’s related to torque.
Additionally, the shaft’s torque will affect how it feels on mishits. Shafts with lower torque will feel harsher and more punishing on mishits. Conversely, shafts with higher torque will feel less harsh when you miss the center of the club face.
Is Zero Torque Possible?
The answers to this question ranged from, “Possible, but difficult” to “Impossible.” What everyone agreed on, however, is that it’s not desirable. MRC pointed out that a shaft with zero torque would transfer very little energy to the golf ball. Others mentioned the drawbacks of extremely rigid feel and the lack of forgiveness
Is Torque Relevant to Steel Shafts?
Most shaft manufacturers report the torque measurement on their graphite shafts, but it’s not a number you typically see on spec sheets for steel shafts. We asked the manufacturers why that is.
In short, torque values are smaller and less variable in steel. It can be measured the same way, but the range of values is not large, so it’s not typically reported.
The reason torque is mentioned more often in relation to composite golf shafts vs. steel is because composite shafts offer so many choices in torque while in steel, such a vast selection simply does not exist.
Steel is an isotropic material meaning its material properties are the same in all directions. Steel is very limited in terms of design. If you want to make a steel shaft stiffer in bending, you can make it thicker and heavier – but that will also cause the torsion stiffness to increase as well. Bending stiffness and torsional stiffness cannot be separated in steel.
Composite materials are anisotropic , meaning their properties vary in different directions. As a structural designer, there is a lot more flexibility in designing with composite materials. For a given bending stiffness shaft, we can vary the torsional stiffness as we see fit to maximize feel and performance. We can also make the shaft heavier or lighter as we see fit while keeping the stiffness in bending and twisting fixed. Composite materials have several advantages over steel in optimizing designs for specific performance requirements.
-Alex Dee, Fujikura
Torque is a function of the shaft’s GJ profile, where G is the shear modulus (resistance of the material to twisting) and J is the shape (diameter and wall thickness). In a carbon shaft, we can vary the G by changing the type of carbon we use of the size of the torsional ply we use. Because of the steels used in golf shafts, G is always the same, regardless of the heat treatment or alloy. And since most shafts have a very similar diameter profile and a small wall thickness variation, GJ, and hence torque, changes very little across steel golf shafts.
-Don Brown, True Temper
Finding the Right Amount of Torque
Overall, faster swingers and players with more aggressive swings benefit from lower torque shafts. More rhythmic swings and players with less club head speed often prefer more torque. However, these are general rules, and there are many exceptions. Feel and shot shape preferences must be considered as well.
Alex Dee of Fujikura said it best, “[Fitters] have the experience to know how specific shafts will work with your swing. I believe our fitters look at the shaft as a whole rather than focusing on one characteristic. The right combination of shaft weight, flex, and torsional stiffness will result in the best feel and ball flight.”
What Have We Learned?
Torque, just like shaft flex, is an important factor in selecting a shaft. Not only does it have a huge impact on the way a shaft will perform, it’s one of the biggest factors in how a shaft feels.
Just as with flex, there are some general rules of thumb for selecting flex, but all the best shaft makers agree: if you want to optimize the performance of your golf clubs, there is no substitute for a proper fitting.