Adjusting Shaft Stiffness with Soft and Hard Stepping
Soft stepping is the term used to indicate changing flex of a taper tip shaft by adjusting the stiffness of a set of irons by putting the lower numbered iron shaft throughout the set. For example, the 8 iron shaft is put in the 9 iron, the 7 iron shaft in the 8 iron and so on through the set. Hard stepping is just the opposite, putting the 9 iron shaft in the 8 iron, the 8 iron shaft in the 7 iron. This practice applies to sets of shafts that are produced with specific designs and lengths for each iron in the set.
When we look at shaft sets we see two design philosophies. The consistent EI weight/flex designs and the True Temper Dynamics design . This is best explained by looking at some EI stiffness charts.The first chart shows the KBS Tour X, S and R flex shafts. The profiles and consistent, simply getting overall stiffer as they get heavier. Most True Temper shafts have different profiles. The tips are not only softer, but longer up the shaft in the R flex model. The tips get both progressively stiffer and shorter in the S and X flex models. In a shaft like the KBS, the difference between and R and an S is simply a little heavier and a little stiffer overall. In the Dynamics design, the profile of the S is significantly different from the R.
Now lets take a look at what happens when these different designs are hard or soft stepped to change stiffness. And, compare hard and soft stepping to changing flex.
Here again is the KBS Tour. Soft stepping, putting the 5 iron shaft in the 6 iron, moves the flex of the shaft about 1/3 of the way toward the R flex shaft. A double soft step, 4 iron in the 6 iron will move the flex another 1/3 toward the R flex. The weight of the shaft changes very little with stepping. The 120 gram S flex is still 120 grams while having a stiffness similar to the 110 gram R flex model.
Now lets look at the same EI chart of the True Temper XP105. We see the same change of profile from hard or soft stepping. A slight change of overall stiffness of the shaft. However, when we look at the R flex shaft we see that it has a significantly different Ei bend profile.
Fitting the True Temper Dynamic Designs
From a club fitting perspective EI Bend Profiles give us a new understanding of fitting the True Temper designs. Adjustment made with hard and soft stepping have a small effect on stiffness and flighting. Adjustment made with flex changes have a significant effect on both stiffness and flighting. To get a precision fitting it is important to work with a fitter that offers the options to hard and soft step the different flex offerings.