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Mizuno ST-X and ST-Z Drivers
With the launch of the Mizuno ST-X and ST-Z drivers, the company hopes to build on the momentum from its previous ST releases while making its case that it belongs in the conversation with the top-selling driver brands in golf.
New Rules
In past Mizuno stories, we’ve discussed how and why the company’s drivers disappeared from the PGA TOUR. When its competitors began buying Tour counts, notoriously frugal Mizuno grew comfortable with its Tour ambassadors not playing its drivers. The approach was to give its staffers plenty of time to work their way into Mizuno driver. More often than not, they never did and the company never said much about it.
For more than a decade, the count of Mizuno drivers in play on the Tour held steady at zero.
Over the past couple of seasons, things have changed. The company has rolled out a fresh approach—a new rulebook of sorts. Like many of its competitors, Mizuno has become increasingly rigid about staffers bagging its drivers. Potential new Tour signings are advised to be absolutely sure the driver is going to work.
As Tour player feedback has played a more significant role in designs like the ST-X and ST-Z, Mizuno’s Tour counts have ticked up, though admittedly “up” was the only mathematically viable option.
Along the way, you may have noticed that Mizuno has accelerated its design process. Iteration is now on the clock with one year becoming the standard cycle for the once more conservative brand. Average golfers—at least those who pay attention—love longer cycles but for Mizuno the extra time became a liability. If a Tour player didn’t like the driver, Mizuno had to wait 1.5 years to try again.
Not exactly a recipe for Tour success. And so, one year removed from ST-200, here we are. The company believes enough advancements have been made that the time for talking is over. If you want to take that to mean that ST is short for Show Time, that’s reasonable enough.
Mizuno ST-X and ST-Z Drivers
Mizuno’s latest one-year-cycle drivers are the ST-X and the ST-Z. Some of you may immediately notice the absence of a low-spin, movable-weight ST-G. The G is sitting out this release cycle but that doesn’t mean it won’t be back.
The X and Z names speak to the distribution of mass within the clubhead. With the ST-X, mass is pushed along the X-axis towards the heel, providing draw bias.
With the ST-Z, mass is pushed along the Z-axis, low and towards the back of the club. The idea is to increase forgiveness while keeping spin under control.
Mizuno’s big picture goals for the ST-X and ST-Z were pretty straightforward: take what was good with the ST-200 and build on it. Evolve the technology, show gains and, while we’re at it, improve the looks, sound and feel of the drivers.
Here’s what Mizuno did in pursuit of those goals.
CORTECH Beta Titanium Face
2021 is shaping up to be the year of the driver face. That’s always true to some degree but this year, more than any other in recent memory, the face is the thing brands are pointing to as the source of speed.
In the case of the Mizuno ST-X and ST-Z drivers, the material itself hasn’t changed from the previous generation. Mizuno is still using Forged SAT 2041 Beta Titanium. Mizuno believes the material is superior to anything its competitors are using.
“Everybody has their material story that’s better than everything else,” says Mizuno’s Chris Voshall. “We have that and more.”
Voshall points specifically to Beta Titanium’s higher strain rate recovery and finer grain structure. The first means the material returns to its shape faster, promoting incremental ball speed gains. The second one means the material is less prone to fatigue which ultimately means greater durability and, more importantly, less CT creep (speed of the face increasing over time).
Mizuno did some reengineering of its driver face topology, strategically thinning an area in the lower portion of the face to boost speed on low face contact but, like most of its competitors, a portion of the speed story comes from tighter tolerances.
As Mizuno has become more familiar with SAT 2041, it has gained a better understanding of how far it can safely push its design targets while still providing consistent parts that conform to USGA rules. One of the easiest ways to gain ball speed is to design to raise your CT targets.
When you have your head fully wrapped around the capabilities of your face material, you can do exactly that.
WAVE Feature Optimization
A signature feature of its metalwoods for the past several generations, both the Mizuno ST-X and Mizuno ST-Z drivers feature a WAVE sole design.
The purpose of the Wave sole is to remove stress on the face by absorbing some of the deflection in the low area of the clubface. Functionally, it’s similar to TaylorMade’s Speed Pocket or Titleist’s Active Recoil Channel. Mizuno says that leads to a larger COR Area (the portion of the face that provides near-max ball speed).
CT Rib structures
I suppose you could say the CT rib structures connecting the top of the Mizuno ST-X and ST-Z driver faces are the top of the heads complement to the WAVE Sole. The features serve to expand the COR area and provide increased durability while ensuring the CT remains within legal limits.
With the three technologies (CORTECH face, WAVE sole and CT Ribs) found in the ST-X and ST-Z, Mizuno is trying to gain speed by taking advantage of the lack of absolute correlation between COR (the USGA’s old standard for governing driver speed) and CT (the current standard).
There’s near-universal agreement that, within that space, there is an opportunity to push speed beyond what the old rule would have allowed for while still remaining under the current limit.
We’re not talking huge gains but there is room for incremental improvement as materials evolve and manufacturing advances allow for more complex geometries to be produced.
Refined Aesthetics
Filed under “aesthetic refinements,” Mizuno has updated the look of its carbon fiber crown. While the entire crown is gloss black, a large portion of it features a visible carbon weave pattern. A broad leading edge surrounds the weave pattern.
The carbon fiber elements on the sole also show off the weave. It’s a small detail but, in one man’s opinion, it makes for a more refined and visually appealing design overall.
With the commonalities covered, let’s look at the individual model details.
ST-X Driver
The Mizuno ST-X is the company’s entry into the draw-bias space. Mizuno understands that draw bias isn’t for everyone (it’s part of the reason why it makes more than one driver) but it’s also hoping golfers will be open-minded about fitting.
The ST-200X got a fair amount of play among Mizuno’s female roster and there’s reason to believe average golfers could benefit as well. The company’s approach is to provide the draw bias many golfers need without trading away all of the forgiveness.
ST-X Driver – Not exclusively long and light
Where the Mizuno ST-X driver differs from the previous model is that it isn’t built to J Spec (Japanese Specification). Unless you want it to be, that is.
J Spec remains an option but it’s not the only option. That speaks to Mizuno’s desire not to pigeonhole the ST-X driver as something exclusively for 70-year-olds.
This time around, the standard ST-X driver is 45 inches with an 11-gram weight screw and a total head weight of 204 grams.
The lightweight and long J Spec version is 45.75 inches with a four-gram weight screw and a total head weight of 194 grams.
Basically, the Mizuno ST-X driver is what you want it to be, which is how it should be.
The Mizuno ST-X driver is available in 10.5 and 12 degrees.
Stock shafts in the standard ST-X driver include the Fujikura Motore X F3 and the Project X EvenFlow Riptide CB (both “real-deal”). The stock shaft in the J Spec version of the ST-X is Mizuno’s M Fusion 40.
Mizuno ST-Z Driver
The Mizuno ST-Z driver is the company’s middle-of-the-market entry. It’s a higher MOI (forgiveness) head designed to produces low to mid spin by keeping the center of gravity close to the neutral axis.
The Mizuno ST-Z is described as offering forgiveness with low spin which is an increasingly common designation within the market place.
Mizuno says the ST-Z driver has a neutral bias (no predisposition to draws or fades). The weight screw is centrally located and instead of a single carbon-fiber sole piece like the one in the ST-X, the ST-Z driver offers two carbon-fiber sole plates balanced on either side of center.
The Mizuno ST-Z driver is available in 9.5 and 10.5 degrees. The 10.5 model is available in RH only. The stock length is 45 inches.
Pricing and Availability
The Mizuno ST-X and ST-Z drivers are $400. Retail availability begins Feb. 18. For more information, visit Mizunousa.com.
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