DeChambeau played seven birdies in eight holes during his eight-under 63WGC-Mexico Championship second-round leaderboard-11 B DeChambeau (US); -10 E van Rooyen (SA), P Reed (USA); -9 H. Matsuyama (Jpn), J. Thomas (USA); -8 R McIlroy (NI) Selected others: -5 T Hatton (Eng), P Casey (Eng); -3 L Westwood (Eng), T Fleetwood (Eng); -1 D Willett (Eng), J Rahm (Spa), S Lowry (Ire); + 5 D Johnson (USA); +8 G McDowell (NI)
The American Bryson DeChambeau called an eight-under-par 63 to take a lead in one halfway through the phase of the WGC-Mexico championship.
The 26-year-old-old placed seven birdies in eight holes and leads on 11 under.
South African Erik van Rooyen equaled the course record on his 30th birthday with a nine-under 62 and shared second with Patrick Reed, who returned a 63.
Rory McIlroy, two nights ahead, made a slow start, but two late birdies left him three shots in the sixth.
World number four Justin Thomas, who twice posted a 62 at the Golf Chapultepec Club, started from the 10th and grabbed six shots in five holes after drilling a 34-foot eagle pit at the first, before he finished in nine.
Van Rooyen, still to be won on the PGA Tour, had nine birdies in a bogey-free round and corresponds to the 2002 round of Retief Goosen for the lowest score of a South African in the WGC e vents.
With birdies rolling around him, McIlroy made a slow start to round two, hampered by a few idiosyncratic drives and then a series of missed putts.
After eight pars bogey he the ninth following a hidden lie in a bunker on the green side and although he had the 12th birdied, he returned the shot by putting the next three times. A towering iron to four feet on the 14th gave him another little bird and some welcome long putts helped him to a round of 69.
Former Masters champion Reed was one of those to darken him, however a 20-foot putt at the 17th creating a fifth birdie in seven holes.
There is no cut halfway through, but defending champion Dustin Johnson stays good on the field at five left, Graeme McDowell birdied the last but is eight left, while Matt of England is Wallace plus nine after three double bogeys in a 77