The initial prototypes of Ping’s new S55 irons were made about one-eighth of an inch larger than their predecessors.

That small of a change would likely go unnoticed in any other Ping iron line: the G-Series, I-Series or Anser irons. But it didn’t cut it for an S-Series iron, which has to fit the eye of a very particular group of testers – tour players.

[quote_box_center]“The [tour] players noticed immediately,” said Mike Nicolette, senior design engineer for Ping. “They all said, ‘I would almost prefer that it would be a little smaller.’”[/quote_box_center]

Such is the crux of creating a “players iron,” whose target audience includes everyone from the best golfers in the world to single-digit handicappers. But unlike most golfers, that audience isn’t looking for more forgiveness, although Nicolette said that it wouldn’t hurt them. They place more value on an iron’s look, feel and workability.

That’s why there weren’t a lot of changes made to the S55 irons – their predecessors, the S56 irons, were already thought of as one of the best-looking, best-feeling irons Ping had ever produced. And for their size, the S56’s were extremely forgiving, and offered enough workability to find their way into the bags of countless professionals. But we’re talking about Ping, a company that prides itself on engineering, so of course there were some improvements that could be made.

In the playing position, the S55 and S56 irons look nearly identical, but as Hunter Mahan noticed when he tested them in the days before The Barclays, the S55’s feel different. That’s because Ping swapped the thermoplastic urethane (TPU) insert that was used on the company’s S56 irons for a thermoplastic elastomer (TPE) insert, which Nicolette said is a more flexible material that is able to absorb more vibration at impact. For most golfers, that will translate into a softer feel.

Click here to see in-hand photos of the S55 irons shot at The Barclays.

The TPE insert, which Ping calls its Custom Tuning Port (CTP), is also larger in the S55 irons than the S56’s, meaning it takes up a greater amount of space in the center of the iron head. That freed up more discretionary weight for Ping engineers to redistribute to the perimeter of the irons, giving them about a 0.5 percent higher moment of inertia (MOI) than the S56’s.

One-half percent more MOI doesn’t sound like a lot, but according to Nicolette, it can make a difference. A 0.5-inch mishit with a 7 iron will fly about 1 or 2 yards farther with an S55 than a S56 iron, Nicolette said, which can big a big deal for a tour player aiming for a tucked pin.

According to Nicolette, the higher MOI of the irons won’t affect workability, as the S55 irons have a similar MOI to the S56’s “above the shaft axis.” Translation: it takes the same amount of energy for golfers to manipulate the club face to their desired position as they approach impact, the definition of workability.

Recent iron releases from Ping have seen the company release sets with progressive sole widths, which means that the long irons have wider soles than the short irons to help golfers hit them higher in the air. That is not the case with the S55’s, which have a sole design that is essentially identical to their predecessors.

But the S55’s do have an element of a progressive design. Nicolette said that the 4-or-so grams of discretionary weight the larger CTP freed up allows the S55 long irons to have a lower, more rearward CG to help golfers hit their long irons higher and farther, while the short irons have a CG that is located more forward in the head to make them fly a little lower.

Maybe the biggest change golfers will notice is with the lofts of the S55 short irons, which are strengthened about 1 degree. That will make them fly a little farther — about 4 yards, Nicolette said. But even though the lofts of the mid and short irons are relatively unchanged (the S55 6 iron measures 30 degrees, 0.5 degrees stronger, the 4 iron measures 0.25 degrees weaker), their lower CG should help them fly a little farther than their predecessors as well, which means golfers won’t have a problem with gapping.

Like the S56 irons, the S55’s are cast from 17-4 stainless steel. But thanks to tour player feedback, their overall size is a little smaller than the S56 irons.

“There’s about a coat of paint difference,” Nicolette said.

The irons will be available at retail Nov. 1 in 3-PW. They will come stock with Ping’s CFS shaft, and will be offered with KBS Tour, True Temper Dynamic Gold or Project X shafts for an upcharge.

Click here to see what members are saying about the S55 irons in the forums.