Paul Walker, an actor made famous for his starring role in the Fast and Furious franchise died at just 40 years old in a high-speed car crash aboard a friend’s Porsche Carrera GT. The 2013 headline was so ironic, every comedian on the planet had to take a swing. Cause of death? Obviously driving a supercar around a parking lot at 90 mph. Add in that the Carrera GT is notoriously hard to handle and it seems like a closed case. Or is it?

The California Highway Patrol’s investigation found that at least two of the car’s tires were nine years old. It concluded that the “driving and handling characteristics”  of the supercar “may have been compromised.”

The plot thickens when you learn that driver Roger Rodas and Paul Walker weren’t just hooning around some random parking lot. In fact, they were outside a business they co-owned: the “Always Evolving” automotive lifestyle hub and store. Rodas arrived at a Sunday afternoon show in a new (to him) Porsche Carrera GT. Walker said he’d never ridden in one, so they took the red car for a spin–on a lap they’d done countless times before.

Automotive journalist Matt Farah knew both men. “I’ve been to that office park, and I know that corner, and you can take that corner at 90 mph in a f—— Prius, as long as you have tires that aren’t 9 years old. In a Carrera GT you could take it at 90, one-handed, while sipping a Venti Latte.”

Farah added, “Roger was a great driver, and actually quite conservative.” He didn’t defend their speeding as legal, but concluded, “from a technical sense, the actual cause of the crash was trash old tires.”

The truth is that rubber breaks down over time. Every year of tires’ life they lose some grip. Many enthusiasts won’t take tires more than five years old to the race track. Many mechanics will refuse to mount a ten-year-old tire on your car. Even if the tread looks perfect.

Why was an A-list celebrity worth tens of millions of dollars riding in a $500,000 car with unsafe old tires? Remember I mentioned that Rodas had just bought the collectible Porsche? The car had just 3,500 miles on the clock and had spent most of its decade-long life in storage. It was still riding on tires from the factory.

Was this tragic accident avoidable? We’ll never know. But if you plan on pushing any car to the limits, take a look at your tires. The few square inches of rubber that connects you to the road are critical for accelerating, cornering, and braking. Make certain you have good tread depth, the rubber isn’t dry-rotted, and the date code is recent.

Never checked tires before? Find out how to read a tire date code. You can also see a simulation of Paul Walker’s crash in the video below: