The South Australian scorched down the hair-raising 1.9km Smithfield Regional Park course in a time of three minutes and 30.47 seconds, with Cairns local Mick Hannah (Polygon UR) (three minutes and 31.069 seconds) just 0.3 seconds off Brosnan in second.
Brosnan was pleased with his ride as he searches for his second world cup win after his maiden victory at Fort William in 2014.
“That was hard, did a lot of pedaling, but it was clean and got all my lines so really happy, ” said Brosnan. “Now I got to back it up.”0
Hannah’s local knowledge, and parochial crowd support on Fan Free Friday, where spectators could line the track without an admission fee, aided his smooth run down the tricky course.
“I just had a great, smooth run. The track has dried up heaps now and I felt good,” said Hannah.
“It is amazing to race at home, so great to race on this track having grown up in the area. Tomorrow should be fun.”
World number one Aaron Gwin (The YT Mob), who took out the first round of the UCI World Cup in France two weeks ago, finished third in a time of three minutes and 31.952 seconds.
Reigning world champion Loic Bruni (Specialized) was fourth (3min 32.126sec), with 2014 Cairns World Cup winner Gee Atherton (Trek Factory Racing) in tenth. Connor Fearon (Kona Factory Team) gave Australia three top ten finishers with a ninth place.
Atherton retains unbeatable status in the women's field
In the elite women’s event, reigning world champion Rachel Atherton (Trek Factory Racing) dominated the qualifying with the fastest time by over five seconds.
Atherton, who recorded the win on the same course in 2014, clocked a time of four minutes and 5.870 seconds to finish ahead of Manon Carpenter (Madison Saracen Factory Team) who recorded four minutes and 11.681 seconds.
Atherton revealed she might still have some left in her for Saturday’s final.
“At one point I was running behind my bike, hands still on the bars and jumped back on, landed on the pedals and carried on just before the rocks,” Atherton said.
She wasn’t the only one to come off the bike, with Cairns hometown favourite and world number three Tracey Hannah (Polygon UR) also taking a spill as she posted the third fastest time of four minutes and 12.200 seconds.
“It was all going good until the little off there at the bottom,” Hannah said. “I think there’s more left for tomorrow.”
Danielle Beecroft, who finished second to Tracy Hannah in the downhill national championships, was ninth fastest (4min 39.303sec) in her first world cup of the season.