Through Sept. 30, the promotion features free 2021 race entry, worth up to a $190 value with the purchase of four eligible tires BY MARK MAYNARD As the official tire sponsor for the U.S. Spartan Race Series, Yokohama is offering a summer promotion that highlights the brand’s tough tires and world’s largest obstacle race and endurance brand. Though the coronavirus has scuttled the 2020 Spartan race season, organizers are focused on 2021. And now through...