Webb Simpson continued his good form to grab a share of the lead at the halfway mark of the Rocket Mortgage Classic.

The American carded an under-eight 64 in the second round at Detroit Golf Club in Michigan on Friday to climb into 12 under at the PGA Tour event.

Simpson already has two wins in 2020 – including at the RBC Heritage in his last start – and shares a one-stroke lead with Chris Kirk (65).

The 2012 U.S. Open champion, Simpson produced a bogey-free second round that included eight birdies.

Kirk was on track to do likewise before a bogey at the par-four 18th.

It remains a packed leaderboard, with Seamus Power (66), Matthew Wolff (64), Bryson DeChambeau (67), Mark Hubbard (66), Ryan Armour (64) and Richy Werenski (66) a shot back.

The in-form DeChambeau has top-10 finishes in his past six starts and backed up his 66 with a 67.

Kevin Kisner (69) and Sepp Straka (66) are in a tie for ninth at 10 under.

Last year's runner-up, Doc Redman, shared the overnight lead but fell back into a tie for 11th after a two-under 70.

Despite a promising start, Rickie Fowler slipped down the leaderboard after a 71, now sitting at six under.

Jason Day's struggles since the PGA Tour resumed amid the coronavirus pandemic continued, with the Australian missing the cut for the third time in four events.