A.J. Allmendinger was leading the 2013 Indianapolis 500. Suddenly, his body shifted inside the car. He looked down and saw his seatbelt was completely open. That major safety failure forced him to pit under a green flag. The extra stop ruined his fuel strategy. It cost him a chance to win one of the biggest races in motorsports.

At 230 mph, a seatbelt failure is a huge danger. A sudden crash could easily throw a driver out of the seat.

A.J. Allmendinger reveals how a seat belt failure derailed his Indy 500 dream

“So it was about lap 105 right around there leading the race, turned off into turn one, and I basically fell against the side of the race car, and I was like, ‘That’s strange. What the heck?’ And I looked kind of as far as I could look down and saw my belt had come undone. My hands weren’t anywhere close to the seatbelt, so it wasn’t like my hands accidentally clicked the belt.”

That moment is still one of the biggest “what ifs” of Allmendinger’s career. In 2013, the veteran of the NASCAR Cup Series made his only Indy 500 race. For a driver who had long loved IndyCar, it was an incredible chance. Penske’s optimism was instantly validated by Allmendinger, who qualified fifth and had one of the fastest cars in the field going into race day.

The opening stages were anything but simple. Allmendinger dropped back in the pack. He drove carefully until he found his rhythm. After he was at ease, he charged through the field, taking the lead by Lap 75 and dominating most of the race. Everything seemed to be coming together with a vehicle that might win the Indy 500.

Then, the seatbelt failed. IndyCars use a heavy-duty six-point harness. This system connects directly to the car’s strong carbon frame. These belts keep drivers safe in high-speed crashes. Because of this, Allmendinger understood right away that there was a severe problem as he abruptly shifted sideways as he entered Turn 1. He found out that the belt had been undone.

At first, he tried to reconnect the belt himself while moving at full speed, but soon found it was not feasible.

In fact, he almost crashed into Turn 3 while attempting to reattach it. There were around 95 laps left. But for a moment he thought about continuing on course until the next planned stop. It was just not worth the risk.

The crew secured the harness during an impromptu trip to pit road. However, it totally undermined his fuel strategy. As Team Penske attempted to regain the lost track position while extending each fuel window, each following stop grew longer. Allmendinger somehow recovered to be in contention despite the setback. He moved up to seventh place from outside the top 10. Before late-race cautions finally dashed his ambitions, he still thought he had a viable opportunity to take the win. Allmendinger never returned to race in the Indy 500 after that 2013 start.

More than ten years later, Allmendinger chose to look back on the event with perspective rather than remorse. His engineer once reminded him that stories are the foundation of racing careers. And few are as remarkable as leading the Indy 500 only to have a seat belt unexpectedly come undone.

It may have cost him the biggest win of his career. But it also gave him a story that almost nobody else in motorsports can tell.