Connor Fields of the United States won the time trial in the second round of the BMX World cup on Friday, while Britain's Shanaze Reade won the women's event.
Fields finished the course in Argentina in 31.892 seconds to beat out France's Joris Daudet, who clocked 31.993, and Sylvain Andre, who finished in 32.167.
Fields was third in the time trial at the season-opening event last month in England.
Reade won the women's time trial in 35.217, beating out Olympic gold medalist Mariana Pajon of Colombia (35.518). Eva Ailloud of France was third and American Brooke Crain was fourth.