Building a car that can reach 250 mph in wind tunnel simulations is one thing. Hitting that number when the rubber meets the road is quite another.
To prove the Speedtail's performance, McLaren turned to Indianapolis 500 winner and McLaren chief test driver Kenny Bräck.
On a winter day in 2019, Bräck pushed the Speedtail to its limits at Cape Canaveral, Fla. Using the space shuttle landing runway as its test track, the car hit 250 miles — in more than 30 test runs.
Palmer marvels at the guts it took for Bräck to do it. Not to mention the tires it took.
McLaren worked with Pirelli to design a tire sidewall that could withstand triple-digit speeds while still offering a comfortable ride at more sensible speeds.
"To make the tire survive 250 miles an hour, the sidewall had to be incredibly stiff to keep it from separating," Palmer said. But it also had to be compliant at lower speeds, "so you're not running on a band of rubber that makes the ride jarring," he said.
The Speedtail tire took months to develop and is emblematic of the challenges of McLaren's approach to vehicle development. Everything on a McLaren — from the lightweight titanium wheel nuts to the carbon fiber — is tailored to the car, Palmer said.
"That way we can guarantee the quality, and we can ensure then it's fit for purpose," he said. "That's why it takes us a good couple of years to design a car."
But it also means engineers are figuring out technical innovations during vehicle development — leaving little room for trial and error.
"In developing Speedtail, we didn't know how to do the mirrors, we didn't know how to do the tires, we didn't know at the start how to make the carbon fiber flex," Palmer said. "We did all these in parallel with the project, which puts a lot of stress onto the team because if that goes wrong and we can't prove it out, then we could have a concept that doesn't work."