Alex Manly and her team know a fierce challenge from Amanda Spratt will have a big say in whether she wins the women's Tour Down Under.

Manly stormed to the overall lead on Monday by winning the second stage at Uraidla in the Adelaide Hills.

The 26-year-old Australian holds an eight-second lead in the overall standings ahead of Tuesday's third and final stage.

That 93.2km stage from Adelaide to Campbelltown features the tough Corkscrew climb, where Spratt and other rivals are sure to ask stern questions of Manly.