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NASCAR Tapered Spacer vs Restrictor Plate Explained

NASCAR has made many changes since the mid-2010s to try and reinvigorate interest in the sport and to create better racing. One change came in the form of adding a tapered spacer. Given their similar qualities to the restrictor plate, you may wonder about the difference between the two. 

NASCAR’s tapered spacers are thicker than restrictor plates, being roughly 1 inch (2.5 cm) thick, with conical walls that allow for more consistent airflow. Restrictor plates were thinner, measuring 1/8 inch (0.32 cm). Both restrict a NASCAR car’s speed, but tapered spacers create less turbulence.

Below, we will outline the major differences between the restrictor plate and the tapered spacer. We will explain what the restrictor plate was, why it was introduced, and why NASCAR decided to replace it with the tapered spacer. We will also discuss how fast a NASCAR car could go without the spacer. 

What Was The Restrictor Plate In NASCAR?

The restrictor plate in NASCAR was a square-shaped piece of aluminum that had 4 holes drilled in the middle. While the holes varied in size between 0.875 inches (2.2 cm) and one inch (2.5 cm), the component itself was no thicker than one-eighth of an inch (0.32 cm). 

NASCAR teams placed this between the car’s intake manifold and carburetor (before carburetors were swapped for fuel injection systems), which restricted airflow into the engine, limiting the combustion that could occur, reducing the maximum power of the engine.

This kept the car from reaching dangerous speeds on NASCAR’s highest-banked superspeedways. When restrictor plates were implemented in 1988, their presence was controversial, with many drivers and teams believing they were responsible for tight racing that often resulted in large wrecks that became synonymous with Daytona and Talladega. 

The reason behind this was that, since the plates reduced speeds, it left the cars driving at similar maximum speeds. This meant cars were closer together, and therefore potentially more likely to crash.

Why Was The Restrictor Plate Introduced In NASCAR?

The restrictor plate was introduced in NASCAR in an effort to reduce the top speeds at the superspeedways. Cars were regularly reaching more than 200 mph, and this posed dangers for the drivers and the fans if there was an accident. Restrictor plates limited engine power, reducing maximum speeds.

In the 1980s, NASCAR cars were getting so fast that their drivers were setting records all over the circuit, culminating in Bill Elliott’s record at Talladega Superspeedway. For a while, the fans were loving the new speeds and it looked as though the cars were only going to get faster. 

Then disaster struck at the 1987 Winston 500 when Bobby Allison’s car blew a tire and went airborne, striking the catch fence and tearing off a large portion of it. Allison’s car would have gone into the grandstands, but two steel beams prevented that, and forced the car back onto the track, but the damage was already done as at least 10 spectators were injured. 

Enter The Restrictor Plate

NASCAR had no choice but to find a way to slow the cars down given the liabilities that would have been present had Allison’s car gone into the fence. With potential comparisons to the 1955 Le Mans Disaster in mind, NASCAR introduced restrictor plates as a way to keep the cars restricted, ideally under 200 mph (320 kph). 

The restrictor plate, however, did not need to be used at every track. Instead, restrictor plates were only implemented at the superspeedways (Daytona and Talladega) unless NASCAR stated otherwise. NASCAR did experiment with restrictor plates at New Hampshire in 2000 after the deaths of Adam Petty and Kenny Irwin Jr earlier that season. 

Both Petty’s and Irwin’s throttles stuck wide open, causing them to hit what was then a concrete barrier head-on. The crashes were eerily similar and they occurred in the same turns, prompting NASCAR to use the restrictor plate at the 2000 New Hampshire race. However, Jeff Burton led every lap, which caused NASCAR to do away with the plate after one race. 

When Did NASCAR Stop Using Restrictor Plates?

NASCAR stopped using restrictor plates in favor of the tapered spacer after the 2019 Daytona 500 largely as a result of safety fears caused by lots of racing in close packs. NASCAR decided to implement tapered spacers to have more control over maximum power outputs.

From the mid 2010s and early 2020s, NASCAR changed a lot of variables. During that time period, we saw the implementation of the chartered system, stage racing, more road courses, the Next Gen car, and even a street course. Often lost in the plethora of changes is that NASCAR stopped using restrictor plates in favor of tapered spacers. 

When the 2019 Daytona 500 rolled around, the restrictor plate sang its swansong. The contraption had been controversial since its debut in 1988, with many NASCAR fans and personnel chastising the horsepower-reducing component, citing that it may not be as safe as NASCAR originally thought. 

Restrictor Plate Criticisms

And you only need to go back and watch a restrictor plate race to know what those in NASCAR spheres were talking about. At Daytona and Talladega, the restrictor plate was often blamed for drivers racing one another in dangerously close packs. And if you ever saw a massive wreck known as The Big One, then you know exactly what they are talking about. 

Such wrecks have led to hundreds of thousands of dollars in damaged equipment, making life tough for owners of smaller teams and their sponsors (not to mention being incredibly dangerous). If the cars made just an inkling of contact, there was a good chance that The Big One would occur. So, NASCAR had to introduce something else to replace the restrictor plates.

KEY POINTS

• NASCAR introduced the restrictor plate in 1988

• They were used to reduce engine power and therefore top speeds

• The last race to use restrictor plates was the 2019 Daytona 500

What Is The Tapered Spacer In NASCAR?

NASCAR’s tapered spacers are used to reduce speeds and target a specific horsepower output. They do so by restricting the amount of air that can flow into the engine, limiting the combustion and therefore the power output, leading to lower top speeds at certain tracks.

With restrictor plate racing, the power output was reduced to anywhere between 400 and 440 HP. With the tapered spacer, depending on the size, engine output can be reduced to around 550 HP

Also like the restrictor plate, tapered spacers reduce airflow into the engine. Without this reduction in airflow, air and fuel would enter into the engine quickly, which would allow the cars to race at dangerous speeds

The Differences 

When you look at a restrictor plate, you will notice that they were nearly paper thin, about one-eighth of an inch thick. By contrast, tapered spaces are thicker, and like restrictor plates, they have four holes, but they are cone-shaped and tapered in a way where they allow a more consistent level of airflow, which makes for better throttle response (which drivers prefer).

Overall, you can consider tapered spacers to be technological upgrades to restrictor plates. The component won out for good when NASCAR did away with restrictor plates following the 2019 Daytona 500. 

Why Did The Tapered Spacer Replace The Restrictor Plate?

NASCAR is a sport that has seen a large decline in ratings between 2006 and 2020. There are many factors at play here, including age of the viewing audience, lack of interest in cars from younger audiences, more competition from streaming or on-demand services, and the fact NASCAR’s races had just gotten stale. 

When the restrictor plate was first introduced, we saw lots of close-pack racing, and adrenaline-pumping side-by-side action. But one of the criticisms regarding restrictor plates was that the tiniest wrong movement could have resulted in a huge crash. Teams, fed up with all the costly damage that were byproducts of restrictor plates, found ways to circumvent. 

Single File Racing

To negate the tight packs, we started to see a lot of single file racing at restrictor plate tracks like Daytona and Talladega. These races would often resemble marathons more than anything else, with teams sitting back and waiting until the final portion of a stage or the race itself before they returned to racing in packs and things got entertaining. 

After having implemented them for a few years, NASCAR discovered that tapered spacers were creating better side-by-side racing than the restrictor plates, given their use at the other tracks since their implementation in 2015. This motivated the switch more than anything else, given the sport’s declining interest that started in the late 2000s.  

While using the tapered spacer full-time has not increased NASCAR’s ratings, it has created a more entertaining product than we have seen in the recent past. The tapered spacer is also a practical improvement over the restrictor plate thanks to its more even distribution of air and sturdier construction.

What NASCAR Tracks Use Tapered Spacers?

All NASCAR tracks use tapered spacers of some kind, although only Daytona, Talladega, and Atlanta use the smaller tapered spacer that decreases the horsepower from 670 to 510 HP. This allows NASCAR to have more control over the speeds of the cars at every track on the calendar.

When NASCAR rolled out the Next Gen car in 2022, they created two different horsepower packages. The first, used at all race tracks, comprised 670 horsepower and a four inch (10 centimeter) spoiler. This package required a larger tapered spacer to reach the targeted horsepower. 

The second package called for smaller tapered spacers to reach the targeted 510 horsepower package. Coming with seven inch (18 centimeter) spoilers, this package is used at Daytona, Talladega, and Atlanta. Both Daytona and Talladega used restrictor plates regularly, while Atlanta’s 2022 reconfiguration gave the track even more speed, requiring the superspeedway package. 

Tapered Spacers Are The Norm

Even in the Generation 6 era, all tracks aside from Daytona and Talladega started using tapered spacers in 2015. In 2019, the Daytona 500 became the final race for the restrictor plate, and since then, all tracks used tapered spacers full-time. 

During the Generation 6 era, they also used two different tapered spacers, with the track size deciding whether NASCAR required a thicker or thinner tapered spacer. Unlike what we listed above, where only three tracks use the smaller tapered spacer in the Next Gen era, 15 tracks, all longer than 1.33 miles (2 km) in length, used them. 

By contrast, the thicker tapered spacers were used at nine tracks in 2019, plus any new road course addition in 2020 and 2021. All tracks that used the thicker tapered spacers did not require aeroducts. 

KEY POINTS

• Tapered spacers replaced restrictor plates after the 2019 Daytona 500

• They offer better air distribution and throttle response

• Tapered spacers are used at all tracks, but they vary depending on the type of track

How Fast Would NASCAR Cars Go Without Tapered Spacers?

It’s likely that NASCAR cars would exceed 210 mph (340 kph) without tapered spacers. Rusty Wallace achieved nearly 230 mph (370 kph) without restrictor plates on his Generation 4 car, but with higher downforce, it’s unlikely that the Next Gen car could match this speed even without tapered spacers.

Tapered spacers have been around since the days of the Generation 6 ride. Before the tapered spacers, restrictor plates kept speeds down at Talladega and Daytona, but that did not mean drivers could not drive around a track unrestricted if there was no one in the grandstands during a practice run. 

The Fastest NASCAR Ever

In 2004, Rusty Wallace did just that, and he drove 228 mph (367 kph) around Talladega. This would have shattered Bill Elliott’s official record set in 1987 when his car reached 213 mph (343 kph). In 2004, the Generation 4 car was still in use. These cars also included carburetors instead of fuel injection, and the cars were, overall, very different from their Generation 6 and Next Gen descendants. 

Note that Elliott still holds the record for fastest-lap during a NASCAR event, since Wallace’s feat occurred during a test session at the track. NASCAR wanted to find ways to improve communications via radio at higher speeds during Wallace’s test session.

Next Gen Era

Like the Generation 6 cars, the Next Gen car can technically reach 850 horsepower. At the superspeedways, practice results show us that these cars can reach average speeds of 192 mph (309 kph) with the tapered spacers and a draft

There has, to date, not been any testing done on the Next Gen car without its tapered spacer. However, since we know that without the restrictor plate the Generation 4 car reached 228 mph (367 kph), and they hit a similar maximum horsepower without the plate, you could see at least similar speeds from the Next Gen car. 

This is compounded by the way air flows over the Next Gen car, which adds roughly an additional 1,000 pounds of downforce, and more grip would make the Next Gen car without a tapered spacer slower than a Generation 4 car in the straightaways, but faster in the banked turns. However, given the amount of downforce, it is not likely a Next Gen car would reach Wallace’s speed. 

Final Thoughts

In NASCAR, the tapered spacer allows more steady airflow into the engine compared to the restrictor plate, creating less turbulence, and allowing for better throttle response. Since 2022, all tracks use tapered spacers to target a specific horsepower, either 510 or 670 HP.