Nancy Armour

USA TODAY Sports

Americans are going to have the ultimate racing machines at the Rio Paralympics.

BMW has designed aerodynamically efficient, carbon-fiber racing wheelchairs that will be customized to each athlete. The wheelchairs, in the making for more than a year, will be unveiled Wednesday as part of the 100-day countdown to the Rio Olympics. They will be made available to select athletes who qualify in the marathon and track events.

“It’s the coolest-looking piece of equipment I’ve ever seen,” said Josh George, gold medalist in the 100 meters at the 2008 Paralympics and winner of the 2015 International Paralympic Committee’s Marathon World Championships.

“It’s an incredibly ambitious project, and these guys have done a phenomenal job. All of us are chomping at the bit to reap the benefits.”

Racing chairs have greatly improved over the last 20 years thanks to technology borrowed from cycling. But BMW’s Designworks, which also was the brains behind the new two-man U.S. bobsled for Sochi, thought it could make the chairs even better by redesigning the chassis and using carbon fiber.

Armour: Older female U.S. athletes still going for gold

Most chairs now are made of welded aluminum. Though it’s a light material, it cannot be molded to fit an athlete’s body like carbon fiber. And, over time, the force exerted by the athletes will cause the chair to bend or flex, requiring the racer to use even more energy.

“Chairs really take a pounding,” said Brad Cracchiola, part of the Designworks team that built the chair. “They’re punching the wheels and a lot of force is going through the chair, translating from athlete into turning wheels. With an aluminum chassis, there’s some flex, and that can take away some of the energy.

“What we really want is to have energy translated as efficiently as possible.”

The Designworks team made 3-D images of select athletes’ chairs and used those as its baseline. Aluminum was replaced with carbon fiber. The cockpit was made more aerodynamic by customizing the seat “bucket” for a better, tighter fit. The steering was redesigned to make it more responsive.

Designworks also took each athlete’s favorite “gloves” — often made of hard putty, they look like pistol grips and help absorb shock from hitting the wheel hundreds of times during a race — and did 3-D scans of them. After cleaning up the surfaces, they produced new ones with a 3-D printer.

“Not only did we manage to get gloves that fit them perfectly and worked great for them, we managed to reduce the weight of them so it’s less mass they have to carry around on their hands,” Cracchiola said.

“These athletes are already incredible athletes,” he added. “What we’re looking to do is give them equipment that rises up to the level of their own talent and really optimizes the efficiency of their performance. So their power and athleticism is transmitted into efficiency and speed.”

George isn’t sure how much faster the new chairs will be; delivery of the chairs begins in about six weeks. But the improved efficiency means athletes will have more energy, and George said that will make a noticeable difference at the end of races.

“If I’m pushing the BMW and other racers are pushing aluminum frames, I’m going to be able to go the same speed as them with less energy exerted,” George said. “That means at the end of a race, the last 5K, the last 10K, I’m going to have more in the tank than they are.”