The last time Matt Downs took his foot off the gas, it was his father who applied the brakes. Dick Downs insisted that all of his sons finish college before they followed him into auto racing, limiting Matt’s teenage speed dreams to the streets of tiny Butterfield, Minn.

Downs honored his father’s wishes by becoming an optometrist. Once he put college in his rearview mirror, he opened the throttle on a hobby that has led him to one of the world’s most storied races: this weekend’s 24 Hours of Le Mans. Downs, 40, is part of a three-man team driving for Boutsen Ginion Racing in the sport’s oldest endurance event.

His wife, Lynn, and his father are part of the entourage that accompanied Downs from his North Mankato home to northwest France last week. After 17 years of moving up the driving ranks, he got his invitation to the 90-year-old race in a most modern manner — through e-mail and Facebook — and will be part of a 22-car field in the Le Mans Prototype 2 class.

Downs will share two-hour shifts behind the wheel with teammates Thomas Dagoneau and Rodin Younessi in a race that begins at 8 a.m. Saturday (Minnesota time) and ends at the same time Sunday. Despite Downs crashing during qualifying Thursday, all systems are go for the three-man team.

“This is a new step for me, and it’s a big step,’’ said Downs, who practices optometry at the Carlson-Tillisch eye clinics in New Ulm and Mankato. “I remember watching [the race] on TV when I was growing up, but I never dreamed I would be in it.’’

More than 250,000 spectators are expected to descend on Le Mans, a city with half that many residents, for a race first run in 1923. Its international character is reflected in Downs’ group: a Belgian-based team featuring two Americans and a Le Mans native, driving a car with a French Oreca 03 chassis and a Japanese Nissan engine.

It’s a big leap for a guy who started out in the Ford Spec Racer class at Brainerd International Raceway in the mid-1990s.

Downs, who graduated from St. John’s and Indiana, later moved into Formula Mazda and IMSA Lite racing and typically competes in a few events each year. After driving in last year’s Petit Le Mans at Road Atlanta, he decided to go all-in on his dream race.

Over the winter, Downs used e-mail and Facebook to contact 15 racing teams invited to Le Mans in search of a driver’s slot in the LMP2 class, which requires at least one amateur — or “gentleman driver’’ in Le Mans parlance — in each car. He did not meet his teammates until recent practice sessions in Belgium and Le Mans.

All will make their debut in a race where teams complete as many laps as they can in 24 hours on the Circuit de la Sarthe, an 8.5-mile course over mostly public roads. Downs’ car will reach a top speed of about 175 miles per hour on a tricky track that tests the durability of both the cars and the drivers.

“The car has to work well, and the drivers have to keep their heads,’’ said Downs, who has prepared by watching video of the course and honing his upper-body strength. “You have to take some risks, but not too many, because you don’t want to damage the car. And with the G-loads on the neck and upper body from the turns and braking, it gets to be a strain.’’

Dick Downs once hoped his own long racing career would lead to Le Mans. He retired from racing a few years ago, but he still will be part of his son’s adventure. Matt Downs is sponsored by Butterfield Farms, a brand of canned chicken made by the family’s company, Downs Food Group of Mankato.

Brothers Lucas and Anthony — who also race and have competed with Matt — will be in France, as well.

Matt Downs said that not many of his patients at the eye clinic are aware of his avocation, but the publicity surrounding his Le Mans debut probably will change that. The race will be televised globally, with the SPEED network showing it in the United States.

After participating in one of the world’s great sporting events, Downs isn’t sure what’s next. He would like to race the 24 Hours of Daytona at some point. And, depending on how things go this weekend, he could return to Le Mans, speeding through a racing life that has been worth the wait.

“For us, if we finish the race, it will be a win,’’ Downs said. “If it’s safe and fun, we’ll consider that a success.’’