In our story on Mizuno’s new drool-worthy Mizuno Pro Iron lineup, we talked about a new approach at Mizuno. Call it a modernization perhaps or simply the necessary adaptation to the changing nature of golf. Evidenced by that Mizuno Pro, however, is the notion that a newly modern Mizuno isn’t likely do anything radical—no red faces on these drivers.
The release of new ST-Z 220 and ST-X 220 drivers is all about steady progression. Improvement without embellishment—performance with universal appeal that still speaks to the guy who loves Mizuno for what it has always been.
With that in mind, don’t expect the ST-Z 220 and ST-X 220 to be radical departures from what came before them.
Premium Beta Titanium CORETECH Face
With previous generations of Mizuno drivers, much of the story revolved around the forged SAT (super alloy titanium) 2041 beta titanium, the material Mizuno uses in its CORETECH faces. The defining characteristic of the material is that it’s stronger and more flexible than the more conventional titanium alloys used on golf clubs. It’s also more expensive, which is a good bit of the reason you don’t see it used more often.
This is a margin game we’re playing, folks.
With respect to beta titanium, stronger means the face is less prone to fatigue, which encompasses things like cracking, flattening and CT creep (the face getting faster over time).
While that last bit might sound like a bonus to us, when it comes to Tour pros and the USGA, CT creep is the stuff of nightmares.
The “more flexible” part means higher ball speeds across the face at a given CT. Mizuno isn’t suggesting it’s skirting USGA rules but, like others, it says beta titanium helps it live on the happy side of the trend line that divides CT (the current USGA standard for limiting how much the face is allowed to flex) and the old COR standard (which has a much stronger correlation to ball speed).
Mizuno ST-X 220 and ST-Z 220 Drivers – Moving Beyond Speed
A few revisions deep into beta titanium, Mizuno thinks it has the speed part figured out so, with the 220 version of ST-X and ST-Z, the company was able devote more attention to stability.
By and large, Mizuno is using stability as a less technical way of describing the moment of inertia (MOI) of its drivers. The idea here is that a more stable driver deflects and twists less when you miss the sweet spot. Less deflection should translate into more ball speed. It’s why higher MOI clubs are described as being more forgiving.
While most MOI or forgiveness stories focus on stability from heel to toe (the golf club’s X-axis), stability from top to bottom (the club’s Y-axis) also plays a significant role in stability, particularly as it relates to creating consistent launch and spin above and below the sweet spot.
The physics is unrelenting. Relative to impact on the sweet spot, high-face impacts will launch higher and spin up to 1,000 rpm less, while low-face impact will result in shots that fly lower and can spin upwards of 1,000 rpm more.
You’re always going to lose a bit of speed on off-center hits but if designers can improve stability by narrowing the gap between high- and low-face contact, golfers should see more consistent results regardless of where on the face we miss.
With that said, how Mizuno went about improving stability is reasonably boilerplate for the golf equipment industry. First, Mizuno’s engineers thinned out the sole and added 40 percent more carbon fiber.
That freed up some weight to be positioned low and back where Mizuno’s tail weights were increased from 11 grams to 20 grams. Every designer would love an extra nine grams to play with and, on percentage, it’s a big number.
Mizuno ST-X 220 and ST-X 220 Stability – By The Numbers
To add some context to this stuff, Mizuno uses a metric it calls Sweet Area. It’s basically the toe-heel and top-down MOI values represented as an ellipse. Compared to the previous models, the sweet area of the ST-Z is 20-percent larger while the ST-X 220’s sweet area is 30 percent larger.
We can throw all sorts of Mizuno robot numbers at you but the takeaway is pretty simple. When it comes to vertical MOI (top to bottom) and Sweet Area, Mizuno says its ST-X 220 and ST-Z 200 get the best of the market leaders.
Mizuno ST 220 Drivers – Two (New) Models
The ST-X 220 and ST-Z 220 join the ST-G 220 to round out Mizuno’s ST-220 lineup. Both new models offer clean lines and appealing sound. Both of those are inherently tricky to quantify as they are, by no small measure, subjective. That said, as acoustic modeling has become more common in the club design world, designers are able to look at a wave form and predict whether most golfers are going to like what they hear. While this hasn’t always been a strength of Mizuno’s metalwoods lineup, in recent years the company feels like it has dialed in a sound that golfers appreciate.
With respect to Mizuno’s naming conventions, the concepts behind each of the new drivers may not be entirely intuitive; nevertheless, they’re intended to convey how weight has been allocated within each head to meet the desired performance specification.
Mizuno ST-X 220
Your refresher from two minutes ago is that the X-axis runs from heel to toe so the “X” in ST-X 220 is a reference to Mizuno moving the center of gravity along the X-axis towards the heel, resulting a bit of draw bias.
Relative to other ST-220 drivers, the ST-X 220 has a more rounded shape and sits square to slightly closed. With allowances for the JPX-EZ irons, Mizuno isn’t one to do anything overtly weird in its designs so while the ST-X 220 is designed to mitigate a slice, it still looks relatively traditional. It doesn’t look like it was designed for slicers which will, no doubt, be part of the appeal and a good bit of the reason why some better players could be drawn to the club.
ST-X 220 Specs
The standard (45”) ST-X 220 is available in 10.5 and 12 degrees. Stock shafts are the Mitsubishi Tensei AV Raw Blue, Aldila Ascent Red 50 and Aldila Ascent UL 40.
The J Spec version of ST-X 200 offers a longer (45.75”) and lighter UST HeLIUM NanoCore shaft.
A 44-inch women’s version (HeLIUM) is also available.
All ST-X 220 drivers are available in right-hand only.
Mizuno ST-Z 220
We haven’t discussed the Z-axis specifically but, in golf club design, it’s the one that runs from front to back. As the center of gravity creeps back along the Z-axis, MOI invariably increases. So the “Z” in ST-Z is meant to suggest that Mizuno has shifted weight back (and also down) to boost the forgiveness of the ST-Z 220 driver.
Compared to the ST-X 220, the ST-Z 220 has a bit more of a traditional pear shape and sits square to slightly open (aka “Tour square” at address).
As with the ST-X, the intent with the ST-Z 220 isn’t to go all-in on one thing. While the ST-Z is more forgiving than its predecessor, Mizuno’s intent isn’t to maximize forgiveness and create something that rivals PING’s G425 MAX or PXG’s XF drivers.
The ST-Z 220 is forgiving but designed to sit along the flagship offerings from TaylorMade, PING, Titleist and COBRA in what I like to call the meaty part of the market.
ST-Z 200 Specs
The standard (45”) ST-Z 220 is available in 9.5 and 10.5 degrees. Stock shafts are the HZRDUS Smoke Blue RDX 60, Mitsubishi Tensei AV Raw Blue (50 and 60 grams), Aldila Ascent Red 50 and Aldila Ascent UL 40.
The J Spec version (10.5°) of ST-Z 200 offers a longer (45.75”) and lighter UST HeLIUM NanoCore shaft.
A 44-inch women’s version (12°) with the UST HeLIUM shaft is also available.
With the exception of the 9.5-degree head, all ST-Z 220 drivers are available in right-hand only.
Pricing and Availability
Retail price for the Mizuno ST-X 220 and ST-Z 220 drivers is $449. Retail availability begins Feb. 3. Available for Pre-Order Now
For more information on the Mizuno ST-X 220 and ST-Z 220 drivers, visit the Mizuno Golf website.
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