Tunku also loved horse racing and was a regular at the Selangor Turf Club. He claimed that his lucky number was 13 and that he would win horse races that were held on the 13th of the month, especially on Friday the 13th for him. Tunku's racing interests included the champion racehorse Think Big. After it won the 1974 Melbourne Cup, Think Big's owners, Malaysian businessman Dato Tan Chin Nam, and Australian property developer Rick O'Sullivan, invited Tunku to join them as a part-owner of the horse. Think Big then won its second Melbourne Cup in 1975.