Rick Price posted a 6-under 64 and is alone in third at Elmhurst Country Club.
Mark Brooks, the 1996 PGA champion, and Greg Owen are knotted in fourth place at 5 under.
Chalmers teed off after Tidland's 63 was posted and broke into red figures with a birdie at 11 (his second hole) and the Australian added birdies at Nos. 14 and 17.
After he made the turn, Chalmers used two sets of back-to-back birdies to match Tidland in first.
'It was as perfect as it could be for playing golf today. It was just absolutely perfect,' said Chalmers. 'I was just fortunate today I kept it under the hole and made some nice putts at the same time.'
Tidland recorded his first birdie at the par-4 third. He fired off three consecutive birdies from the fifth to get his round going and found himself at 5 under par after a birdie at 11.
Tidland hit a wedge to 10 feet to set up a quick birdie putt at 17.
'I was literally trying to hit the putt 6 inches and it just wiggled down,' said Tidland. 'It looked like it was going to miss and then it drifted in. It was one of those days where that kind of putt is falling.'
Tidland closed with a final birdie at 18.
'I just played solid on the front,' said Tidland. 'I've been playing okay, nothing great. This round was just some made putts at some key times and some nice up-and-downs of ones that I wouldn't normally be getting.'