Gladys Berejiklian says she is "bracing" herself for "huge swings" against the Liberal candidates in Saturday's byelections, predicting the contests "will come down to the wire".

"Byelections are never easy for governments," she said. "I knew we'd be doing it tough in all three seats."

Ms Berejiklian was out campaigning on Friday with the Liberal candidate for Manly, James Griffin, North Shore candidate Felicity Wilson and Gosford candidate Jilly Pilon.

Asked what issues were being raised with her by voters in North Shore and Manly, Ms Berejiklian said most people were concerned about traffic, not the issue of forced council amalgamations.