Are The New Srixon ZXi Irons Really “Groundbreaking?”

Srixon isn’t a company prone to hyperbole.

Like stablemates Cleveland and XXIO, Srixon follows the Kaizen principle of steady, continuous improvement. That thinking stifles the usual marketing buzzwords like “revolutionary” or “groundbreaking.”

So when Srixon does use marketing buzzwords like “revolutionary” and “groundbreaking,” one tends to notice. When it says its new forging process – “i-Forging” – is, and I quote, “the greatest innovation in iron metallurgy ever,” it’s time to stop whatever the hell it is you’re doing and start asking questions.

Which is what we did. The answers were fascinating.

I’m no metallurgist so we can neither confirm nor deny that “i-forging” is, in fact, the greatest innovation in iron metallurgy ever.

We can, however, say that anytime you mess with a winning formula, it’s a risk.

Srixon, my friends, is thumbing its nose at that risk and is pushing in all its chips on what it believes is a winning hand.

Srixon ZXi irons: Process and materials

Normally, when you have top-performing forged irons with a cult-like following, R&D’s prime directive is simple: Don’t f”#k it up. Whatever metallurgical magic is going on with the new Srixon ZXi irons, it’s not obvious to the naked eye.

“With ‘better player’ products, it’s about invisible innovation,” says Srixon Engineering Director Dustin Brekke. “How can we make them better and provide new results without changing them from a player’s perspective?”

The answer is i-Forging.

“i-Forged is a holistic approach of improving feel while being performance and impact-focused,” explains Brekke. “We want to improve feel without making any negative performance tradeoffs.”

i-Forged is the catchy name etched into each iron’s hosel and it’s the “i” in ZXi. The technology itself is called “condensed forging.”

Condensed forging is a proprietary technique where carefully shaped protrusions are pressed into key locations of the clubhead. The forging hammer pounds those protrusions into those key areas. The piece is then reheated and pounded again.

“The final product is still smooth and polished,” says Brekke. “It’s an extra step in our forging to bring condensed grain structure to areas where more strength is required.”

Specifically, condensed forging alters the atomic patterns of the steel and makes those key areas – the hosel of the ZXi7 and the hosel, topline and toe of the ZXi5 and ZXiU utility iron – stronger. That added strength is important as it allows Srixon to start with a softer overall material.

With irons, soft is good. Soft and strong is better.

Condensed forging simplified

Last week, we told you about Mizuno’s new hydraulic press to forge its new JPX 925 Forged irons. The new press varies the pressure and duration of those pressures during the forging process. That allows Mizuno to reinforce the neck and topline so it can mill a much thinner face.

Condensed forging is a different process for a similar purpose but with a different result in mind. Those strengthened areas allow Srixon to use softer, better-feeling materials that otherwise wouldn’t hold up.

“Going softer is easy but there are tradeoffs,” says Brekke. “You might wind up with a club that’s deforming, losing its loft and lie and can’t survive normal wear and tear. At the grain structure level, condensed forging lets us condense the grain configuration so we can add strength into focused areas.”

The new Srixon ZXi7, ZXi5 and ZXiU utility irons all carry the i-Forged label. According to Srixon, each one is noticeably softer feeling than their ZX Mk II predecessors. The cast ZXi4 is a different animal altogether.

Srixon ZXi irons: “Parade of Softness”

Condensed forging lets Srixon use soft S15C steel in the new ZXi7 irons. S15C is Japan’s version of 1015 carbon steel (the Mk II was 1020) and is the softest material Srixon has ever used in an iron.

There’s no variable-face thickness for AI to design in a single-billet forging but Srixon is using AI to enhance the ZXi5’s PureFrame cavity. The new design features a wider, thicker ridge forged into the cavity directly behind the sweet spot. Srixon says that stiffens the area around the impact zone which reduces face deformation and vibration at impact.

The Srixon ZXi5 and ZXiU utility iron bodies are condensed forged from S20C (or 1020) carbon steel. Their faces are high-strength SUP10 stainless steel, often referred to as “spring steel,” with a new heat treatment process.

“With stronger lofts, you can get warpage in the face if you use too soft a material,” says Brekke. “The heat treatment for the face gives a softer feel and great flexibility for ball speed without sacrificing durability while condensed forging strengthens the frame.”

Additionally, both the ZXiU utilities and the ZXi5 long- and mid-irons feature tungsten weighting near the sole to get CG down and keep spin low.

The Srixon Zxi4 body isn’t forged. Instead, it’s cast from SUS 17-47 (similar to 17-4 stainless steel). Again, heat treatment plays a key role.

“We want to maintain strength and durability while keeping the hosel soft for bendability,” says Brekke. “Bendability is important when irons are meant to be blended.”

The ZXi4 face is made from HT 1770 maraging steel, the same as the previous model.

“It has a high-yield stress so it’s not going to wear or deform,” says Brekke. “It can be made very thin with a very high rebound.”

Mainframes and multi-pieces

The new Srixon ZXi5, ZXi4 and ZXiU utility irons are all multi-piece construction. Unlike the ZXi7, all three feature Srixon’s MainFrame technology, an AI-designed variable-thickness face to maximize ball speed over a wider area.

The ZXi5 replaces MyGolfSpy’s reigning Best Player’s Distance Iron, the ZX Mk II. Srixon says its testing shows the ZXi5 to be 14 percent softer than its predecessor while a wee bit (two grams) of repositioned mass lowers CG and increases MOI and ball speed.

Materials aside, the Srixon ZXiU utility irons are probably getting the biggest makeover in the line. It has morphed over the years from a squat, Barney Rubble-looking club into a sleeker, more blade-looking iron. It has the widest sole in the ZXi line but with minimal offset. The new utility line also is getting Srixon’s signature V.T. Sole for the first time.

“There’s more attack angle with a utility iron compared to a hybrid or a fairway wood,” says Brekke. “The V.T. Sole and the notches on the heel and toe are important.”

The linchpin holding the Srixon ZXi irons together

Srixon ZX MK II irons were across-the-board strong performers in MyGolfSpy testing last year. As mentioned, the ZX5 Mk II was the top dog in the Player’s Distance category. The ZX7 finished fifth overall in Player’s Iron testing while the ZX4 finished a very strong third in the Game-Improvement category.

The Srixon ZXi irons are a family, however, and are meant to be blended. Since the ZXi4 is cast and not forged, it’s the key to making the whole thing work. Srixon has to get the sound and feel in line with the rest of the family.

“We did a whole bunch of sound and vibration analysis,” says Brekke. “The weight pads, wall thickness, internal ribs and everything have to be right. We’re not sacrificing feel for anything.”

The ZXi4 is hollow-body construction and Srixon has been able to fine-tune feel without using urethane or any other filling to enhance it. Usually, hollow-body irons without urethane feel like crapola so what Srixon has pulled off is borderline remarkable.

“We’re not going for that maximum size like a super game-improvement iron,” Brekke says. “That’s where you can start to lose sound and feel. They can get clicky or clanky because they’re too large and the walls are too thin. You’re trading feel for forgiveness.”

Feel, forgiveness and family

Normalizing feel and forgiveness across multiple family members is the key to blending. Titleist aced this with its T-Series irons as did Mizuno with the Pro 241-243-245 line.

That’s why the ZXi4 is so important. The Srixon ZXi irons already ace the visuals of blending, even better than Titleist and Mizuno. The ZXi7, ZXi5, ZXi4 and ZXiU toplines are all the same thickness, six millimeters. Blade lengths get longer and offsets get wider but the differences are shockingly small. For example, the ZXi4 4-iron blade is only 2.6 millimeters longer than the ZXi7 pitching wedge. The offset difference between the ZXi7 and ZXi4 7-irons is 0.4 millimeters. If you can pick that up, you have way better eyesight than I do.

“The irons work as a family,” says Brekke. “They’re innovated together from face performance to sole performance. Starting from sketching and initial modeling, it’s our target objective.”

We’ve tested samples of all three iron sets plus the ZXiU utility. As you’d expect, they blend very nicely visually. Because our samples had different shafts, we couldn’t get a true handle on feel consistency but we can say all three irons felt like Srixons should. The utility iron and I had some issues but when struck squarely, it feels like a Srixon, too.

As a family, the new Srixon ZXi irons should be a fitter’s delight. The visual flow won’t confine you to the traditional 7- to 8-iron transition. Since the toplines, blade lengths and offsets are so close, you can transition wherever it makes sense. You could piece together a ZXi7 9-iron and pitching wedge with a ZXi5 6- through 8-iron and a Zxi4 5-iron kicker.

“It’s not the ZXi5 or ZXi7 iron set,” says Brekke. “It’s the ZXi irons and then it’s how are you going to piece it together.”

Srixon ZXi irons: Specs, price and availability

For a set intended for blending, stock specs are, for the most part, academic.

The Srixon ZXi7 and ZXi5 irons come standard with the True Temper Dynamic Gold Mid 115/110 shaft. The ZXi5 also offers the KBS TGI Tour Graphite and the UST Mamiya Recoil Dart 65 as graphite options.

The ZXi4 stock shaft is the KBS Tour Lite with the UST Mamiya Recoil and KBS TGI as graphite options. All three irons are available in left- and right-handed. The Golf Pride Tour Velvet 360 is the stock grip for all three sets.

The ZXi4 is also available in a women’s model with the UST Helium Nanocore 50 shaft and Lamkin ST Soft grip standard. It’s also available in left- and right-handed models, although lefties will have to custom order theirs.

The Srixon ZXiU utility irons come in three lofts: 18, 20 and 23 degrees in both right- and left-handed. The Mitsubishi MMT Utility shaft and Golf Pride Tour Velvet 360 grip are stock.

Srixon continues to offer free Arccos sensors and an Arccos Caddie trial via a QR code on the grip endcap. If you want a dash of color, Srixon is continuing its custom paint-fill program. You can choose from 20 color options and five different locations for 15 bucks.

The Srixon ZXi iron series will retail for $1,299.99 for a seven-piece set, just under $186 per club. The ZXiU utility irons will go for $249.99. They all hit retail Jan. 24.

For more information, visit the Srixon website.