The new custom driver that has Phil Mickelson atop the PGA Championship

Kiawah Island is the longest course in major championship history so it should be no surprise that a new driver has been key to Phil Mickelson’s success halfway through the PGA Championship.

Mickelson, 50, held the lead after Friday’s morning wave thanks to rounds of 70-69. He ranked first in Strokes Gained: Tee-to-Green, in the top 10 of Strokes Gained: Off-the-Tee and averaged 298 yards off the tee.

This is the first week that Mickelson is using a custom Epic Speed head that effectively has 5 degrees of loft. The shaft is 47.9 inches, pushing up against the USGA limit of 48 inches.

“It’s like working with a long-drive competitor at that point,” said Gerritt Pon, Callaway’s senior club performance analyst. “He’s not using it for accuracy. He’s using it for distance. Interestingly enough, he’s the type of player who does not necessarily lose accuracy with the longer shaft. Some lose a tremendous amount, some actually gain a little bit, but he’s the type of player who doesn’t lose accuracy. But he gains speed.

“To swing the longer shaft, he’s trying to hit up on the ball a little more than with a normal shaft. He’s creating a lot of loft at impact to launch it high, so the main things that had to be accomplished was making the driver low-spin and fast.”

Mickelson’s new Epic Speed, which was built especially for him, features Callaway’s aerodynamic Cyclone head shape. A second screw was added to the front of the head to lower the center of gravity.

“With faster swing speeds, you see more benefit from the aerodynamically-designed head,” Pon said. “He has a driver that is fast, easy for him to draw, mitigates the left miss (for a left-hander) more than some of our other models that are popular on TOUR, and is very low spin.”

Mickelson tested an 8.5-degree model of the Epic Speed that was lofted down to 6.5 degrees but that head created too much spin. He wants his draws to spin under 2,000 rpms and his fades to spin under 2,400, Pon said.

If Mickelson were right-handed, the increased number of offerings available may have made it easier to find a match for him. Making a head that fit Mickelson meant designing a new head in CAD and then working with the foundries to have it produced. That is typically an eight-week process, Pon said.

“We started with a baseline of the Epic Speed, which was a long time in the making, and then modified it with Phil in mind,” Pon said. “This particular model of the Speed is pretty new. Even though it looks like the same Epic Speed, it’s a customized version for a left-hander who’s trying to swing a long shaft with low loft and low spin.

“So basically Phil Mickelson.”