Why do NASCAR drivers use restrictor plates on certain tracks? All you need to know

Restrictor plates are used in NASCAR to limit the power of engines, thereby reducing the speed of cars on specific tracks for safety reasons. NASCAR introduced the restrictor plate in 1988 and it was a crucial safety component in the sport.

The Cup and Xfinity Series drivers use restrictor plates to address the danger of high speeds on superspeedways like Daytona International Speedway and Talladega Superspeedway. Cars without restrictor plates on these tracks can exceed speeds of 190 mph, which increases the risk of accidents and the severity of crashes.

At high speed, Next Gen cars are more likely to become airborne during collisions. Restrictor plates help mitigate this risk by slowing the cars down.

The restrictor plate is a small, thin metal plate with four small holes that is placed between the carburetor (or throttle body) and the intake manifold. These holes control the amount of air and fuel mixture entering the engine, which in return reduces the horsepower and top speed of the car.

The restrictor plates were created after late Bobby Allison’s horrific wreck at the Winston 500 at Talladega Superspeedway in 1987. Allison’s car went airborne and nearly flew into the grandstands at over 200 mph. NASCAR recognized the need to slow the cars down at superspeedways like Talladega Superspeedway and Daytona International Speedway.

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A transition from restrictor plates to tapered spacers after the 2019 NASCAR season

There was one drawback with the restrictor plate: by slowing all the cars down, the plates caused the field to bunch up into tight packs, leading to pack racing. While this makes for thrilling competition, it also resulted in massive multi-car wrecks.

With engines restricted, differences in driver skill and car setup may play less of a role, making the racing feel more about drafting strategy than individual performance.

To provide smoother throttle response and improved engine performance, NASCAR replaced traditional restrictor plates with tapered spacers in 2019, which serve a similar purpose but allow for more control over engine power. This change was part of NASCAR's move to the Gen-6 and later the Next Gen car packages.

Restrictor plates were used for several years in the sport, shaping some of the most memorable moments in the sport but also sparking debates about safety versus competitive racing. These plates, or their modern equivalents, remain a defining element of sport’s high-speed superspeedway racing, balancing the thrill of speed with the imperative of safety.