After passing his rookie test in 1961, Duman made an attempt to qualify with the Ray Brady Special but the run was incomplete. In 1962, he qualified the Stearly Motor Freight Special, but was bumped and wound up as the second alternate. In 1963, he was entered in the Federal Engineering Special, but crashed during practice. Duman finally qualified for the Indianapolis 500 in 1964. Driving a sponsor-less pink and black Trevis-built Watson/Offy entered by Nick Fulbright and Dave Paul. It was the same car driven by Allen Crowe in the 1963 race. Duman qualified 16th on pole day, but ended up the 32nd-overall fastest qualifier. He narrowly held on to make the lineup on bump day, as the second-slowest car in the field. The team received sponsorship from the Clean Wear Service Company - a local laundry service that was frequented by the drivers and crews during the month of May - just prior to the race. Duman was involved in the fiery crash that took the lives of Dave MacDonald and Eddie Sachs. The accident happened in front of Duman, and as he approached the crash scene, he attempted to miss both Sachs and MacDonald. However, in the fiery melee, the Novi of Bobby Unser knocked Duman's car from behind, and sent the car spinning to the inside wall. The car erupted in flames, but not before Duman was able to climb out and escape to the grass infield. Duman was hospitalized with second and third degree burns, and missed over two months of racing while he recuperated. After recovering from his injuries, Duman qualified for the 1965 race in the Travelon Trailer Special. He ran as high as 12th before dropping out. In 1966 race, he started last and became involved in the opening lap crash, finishing last. In 1967 race, he finished 23rd driving the REV 500 Special for J. C. Agajanian. Duman's final Indy 500 start came in 1968 race. On the final turn of the final lap, Duman's engine blew coming out of turn four, and he coasted across the finish line to finish 6th. The 1968 race would be his best result at Indianapolis, as just over a one-week later, Duman was killed in a crash at Milwaukee.
Indianapolis 500 results
Awards and accomplishments
Duman was the only USAC Champ Car driver to race a front-engine upright 'dirt-style' car on a road course and a rear-engine car in a USAC championship dirt car race.
Less than two weeks after he finished 6th at the 1968 Indianapolis 500, Duman was at the next race of the USAC Championship season, the Rex Mays Classic at Milwaukee. Duman started 14th in the 24-car field, driving the Central Excavating Gerhardt Turbocharged Offy. On the third lap, the cars of Bay Darnell and Norm Brown reportedly got tangled in turn one. Both cars slid towards the outside wall, collecting Duman in the process. Duman's car tipped over and began barrel-rolling before it flew into the catchfence cockpit first. After Duman's car bounced back down the track, both Darnell and Brown's car slammed the outside wall and the three cars came to rest on fire. Darnell and Brown suffered minor burn injuries, but Duman was killed instantly from massive head injuries when the cockpit of his car struck the catchfence. His helmet had been shattered and pulled from his head. Eight spectators were also injured by the flying debris which cleared the catchfence. Ronnie Duman is interred at Crown Hill Cemetery in Indianapolis.
