The new Mizuno ST190 family of drivers and fairways reveals that innovation in metalwoods needs more than some single element improvement. As David Llewellyn, vice-president of research and development, terms it, sometimes success is really about the right collection of elements in the right order and the right amount. It’s like if you’re going to make a better chocolate cake: it’s not as simple as just dumping a whole lot more chocolate into the recipe.
The new ST190 metalwoods, led by the high-forgiveness ST190 and the multi-adjustable ST190G drivers, incorporate advancements in a number of hallmark Mizuno technologies. Those include rare high-strength titanium alloy, a carbon composite crown, a wave-structure on the sole and optional levels of adjustability. Improving the mass properties like centre of gravity (CG) location, stability on off-centre hits (moment of inertia, or MOI) or ball speed through a face design with a better spring-like effect (coefficient of restitution, or COR) is where the ultimate focus has to be, Llewellyn said.
“I think having a large COR area, having a sufficient MOI, having the sweet spot and CG where it needs to be so that you produce the appropriate spin rates. It’s really about checking all those boxes and getting that recipe just right,” he said. “This is really about a further optimisation of a lot of things that were already in play for us.
“I feel like that ST190 recipe is really really good.”
The two new Mizuno ST190 drivers get those performance benefits from two features that have been refined from past models. First, the new drivers continue the use of SP-700, a beta titanium with a high-strength to weight ratio to improve the face’s overall flexibility. Mizuno first used the alloy in last year’s ST180 and GT180 drivers, and Llewellyn said that among its key benefits are that it is 10 percent stronger than typical basic titanium alloys used in drivers like titanium 6-4.
But again, it’s not just the use of the SP-700 alloy in the face that makes the new drivers better, Llewellyn said. It’s how the face material and design are impacted by other elements of the driver. And another big part of that recipe is the wave sole structure that’s been used in Mizuno metalwoods of the past, including last year’s ST180 driver.
The modified wave pattern on the new drivers includes a deeper initial wave that contributes to the face flexing at impact, and it also concentrates more mass low because more material is required to create the wave structure. But it also affects the way the face can be designed in another important way.
“Another thing we’re doing by having the wave there is we’re actually reducing the amount of stress on the face,” Llewellyn said. “If you limit all that stress and strain of impact to just the face, then you’ve got to reinforce the face more. Because we’re able to spread that impact stress to the sole by allowing the sole to flex, then you can make the face lighter so it doesn’t have to take as much stress. So you can then make the face bigger.”
The Mizuno driver recipe also includes a carbon composite crown that saves seven grams to lower the CG even more, helping these drivers achieve lower spin numbers than past Mizuno drivers, an increasing area of appeal for higher swing speed players who are looking to knock off spin.
Those players and others who prefer the benefits of adjustability will be drawn to the ST190G, which features two tracks in the sole that make room for two freely moving seven-gram weights. The larger profile ST190 features a six-gram fixed weight in the rear perimeter to produce more forgiveness and higher flight.
The ST190 also includes a family of fairway woods, each featuring a composite crown and the wave sole geometry. Ball speed is bolstered by a high-strength steel alloy (MT1770) in the face. Again, it’s the combination of the wave structure and face working together to improve performance.
“The ST190’s deeper face is not just useful from the tee – it also gives the clubface a larger frame that functions more like a driver for higher ball speed,” says Kei Tsjui, Mizuno senior club engineer. “Normally that is compromised by a higher sweet spot and additional backspin, but by using our carbon composite crown and Wave Soleplate, we were able to combine high ball speeds with an efficient ball flight.”
The ST190 fairway woods are available in both an adjustable hosel “Tour Spoon” model that fits a loft range from 13-17 degrees, as well as a fixed hosel 3-wood and 5-wood.
The ST190G driver ($799) is available in a 9-degree model, while the ST190 ($729) comes in both a 9.5 and 10.5 model. Each features an adjustable hosel that changes loft by plus/minus two degrees. The adjustable ST190 Tour Spoon will be $449, while the fixed-loft ST190 fairway woods will sell for $399. The ST190 metalwoods will be in Australian stores next month.