WHAT YOU NEED TO KNOW: Two new models join Mizuno’s ST line of drivers, the ST-X 220 and the ST-Z 220, and both use expanded carbon-composite sections in the sole and crown to create more stable heads designed to produce more consistent launch conditions all over the face.
New ST-Z fairway woods and hybrids also emphasise consistency and forgiveness, including an oversize titanium 3-wood built for off-centre hit stability and higher launch.
PRICE: ST-X 220 and ST-Z 220 drivers are $999 each. ST-X fairway woods are $579. ST-X hybrids are $429.
THE DEEP DIVE: If new clubs weren’t selling distance, we’re pretty sure they wouldn’t be selling, period. But in reality what most average golfers want, especially those who aren’t practising six days a week, is consistency. They want a reliability to their game, and they’d be especially pleased if that reliability even exceeded their skills. That’s what Mizuno is seeking to accomplish with its latest additions to the ST driver family, the deep centre of gravity ST-Z 220 and the heel-biased weighting of the ST-X 220, as well as with new ST-X fairway woods and hybrids.
“We’re not really going to be able to make your swing better,” said David Llewellyn, Mizuno’s director of research and development. “What we can work on is designing the clubhead to get more consistent results. If you typically go through a fitting, you get your best numbers as close to optimal as possible, but what is happening on a mis-hit? Not only are you losing distance in the sense that the ball is losing energy because the head is rotating, but also your launch parameters are getting skewed from not being close to optimal. We want to make sure those launch parameters are stable as possible. We’re really focusing on launch stability for launch angle and backspin.”
Those are essentially the primary improvements behind the new ST-Z 220 and ST-X 220 drivers, two new complimentary models the adjustable weight ST-G 220 driver, introduced in the fall. It’s about increasing the stability of the head on off-centre hits, or moment of inertia. Also known as resistance to twisting, the MOI is typically thought of in the heel-toe, or horizontal, direction, which is how the USGA limits forgiveness. But it’s also important in the crown-sole, or vertical, direction. The more stable the head, Llewellyn explained, the more consistent ball speeds are, but so too is spin. If the crown-sole MOI is insufficient, it can mean that the difference between an impact high on the face and one low on the face might be as much as 2,000 rpm. That will mean a big difference in total distance, even if ball speed doesn’t change that much on an off-centre hit.
“These head designs are more efficient for vertical MOI, and that’s giving us more consistent launch angle and spin rate,” Llewellyn said. “The head’s just not deflecting as much on a mis-hit.
“How we’re able to do that is by creating more discretionary weight. In the past, it’s been kind of an incremental improvement. This round has been more than an increment.”
The discretionary weight comes by way of a 40 percent increase in the amount of lightweight carbon composite used in heel and toe panels on the sole to go along with the large carbon composite crown in both the ST-X 220 and ST-Z 220. That frees up the body to make room for a 20-gram sole weight low and in the rear perimeter, almost double compared to past models, for more forgiveness and lower spin. The ST-Z 220 pushes the centre of gravity deeper but also keeps it centred (along what’s called the Z-axis) for broad forgiveness across the face on off-centre hits.
The ST-X 220 also keeps the CG farther back from the face, but shifts it slightly closer to the the hosel, or along the X-axis. A rear but heelward back weight provides additional draw bias to help fight a slice. By comparison, it will produce a little higher spin than the ST-Z, another nod to average golfers at more moderate swing speeds who might benefit from a little more spin for greater carry distance.
Both drivers feature a new variable thickness design on a high-strength SAT2041 beta titanium face, further improving off-centre hit performance. That distinctly strong and flexible alloy first debuted in Mizuno’s ST200 drivers from two years ago.
Each driver also utilises an adjustable hosel that tweaks loft and face angle by plus/minus two degrees. In the standard setting, the ST-Z 220 sets up with a neutral to open face angle at address, while the ST-X 220 features a neutral to closed face angle.
As both drivers break new ground for Mizuno for forgiveness, so too is that the direction for the ST-X fairway woods and hybrids. That starts with a larger volume 3-wood (191 cubic centimetres) with an all-titanium construction, including the same SAT 2041 beta titanium alloy in the face found in the drivers. That creates more ball speed, while a low, deep CG helps with higher launch. The crown features an internal waffle pattern to further thin the titanium and help to lower the CG, as well. Also adding to the easier launch is the 16-degree loft, and the latest iteration of the accordion-like wave pattern at the front of the sole. The latter increases the potential flexing in the face, especially on lower face impacts.
A further forgiveness benefit on the ST-X 3-wood is the slightly heelward CG for additional draw bias. That’s made possible by setting the hosel axis slightly more in board for a shorter distance to the CG.
The 5- and 7-wood on the ST-X fairway woods use an all-steel construction, including a high-strength maraging steel (MAS1C) in the face insert.
Similarly, the ST-X hybrids use a thin MAS1C face insert (as thin as 1.8 millimetres), and they also feature the waffled crown to help lower the CG. Like the fairway woods, the hosel axis is again set more in board on the head, effectively moving the CG slightly more towards the heel for a small draw bias. The CG is also slightly deeper compared to Mizuno’s CLK for more forgiveness.