Mark Wiebe of the United States shot a 5-under 65 Friday to share the lead with Bernhard Langer after the second round of the Senior British Open at Royal Birkdale.
Wiebe had four birdies on the back nine. Langer, the 2010 champion at Carnoustie, shot a 67 and made five birdies. Both players finished at 5-under 135.
"I really got my irons zoned in on the back nine," Wiebe said. "I know there's a long way to go, but I'm tickled to be where I am. It was unbelievable and great to shoot the low round."
Wiebe moved to 1 under by the turn with two birdies and a bogey. He had three birdies in four holes from the 13th and added another with a 15-foot putt at the last.
The German dropped two strokes at No. 6 when he double-hit the ball.
"The ball was sitting up in the long grass and I caught it high on the clubface and again on the follow through," said Langer, a two-time Masters champion. "But that was my only blemish. Most of it was impressive and good, and I putted a little better today."
David Frost of South Africa (68) finished a stroke back in third. He picked up birdies at Nos. 2, 5 and 9 to move to 5 under. He faltered slightly on the back nine, dropping shots at the par-3 12th and 14th before a birdie at No. 17.
"It was a bit of a shaky round," Frost said. "I didn't feel comfortable with the club in my hand. I hit some wayward shots, but managed to hit good irons into the greens and the putter was my savior."
Tom Watson, Frost's playing partner, only got going after a front nine featuring two birdies, two bogeys and a double bogey. The American made long putts at Nos. 11, 12 and 13 and holed another birdie at the 15th. He bogeyed the last two to finish at 4 over.
Overnight leader Gene Sauers shot a 70 for a share of fourth place with Peter Fowler (68) and Mark McNulty (67).