Paul Roy repairs a bike at Roy’s Bicycle Shop in Lewiston on Thursday. Both Roy’s and Rainbow Bicycle and Fitness in Auburn have seen a large increase in business because of the upcoming Dempsey Challenge, said Roy, and John Grenier, owner of Rainbow. A lot of people have been training for the Challenge and bike tune-ups have been in high demand, said Roy’s wife, Marielle. The benefit ride “has stimulated a lot of road bike sales, especially with women,” Grenier said. “Sales to women have tripled,” said Grenier, who typically sells one road bike to a woman for every eight to men. The ratio has been 1-to-1 this summer, he added. Rainbow’s busy season started a month early this year and Grenier believes the Dempsey Challenge is directly responsible. Paul Roy, a retired Lewiston firefighter, said road tires have been a hot item this year as people get their bikes, as well as themselves, in shape for the Challenge. The Dempsey Challenge is Oct. 4 and features four different bike rides of up to 100 miles. Registration is closed as the event’s cap of 3,500 participants has been reached.