How Impound Races Work

Impound races require the set-up of the car not to be changed during the race. See more NASCAR pictures.
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Before impound racing, NASCAR knew it had to find a balance between drivers who could afford to use one setup to qualify in a race and another in the actual race, and drivers who had to make do with a single setup. Implemented in 2005, the impound rule dictates that a car's setup cannot be altered between the qualifying competition and the actual race. Once a car has qualified and been inspected, crewmembers are not allowed to perform any work on it. The car has to be parked in the garage (impounded) and left alone until the race [source: Siska]. Though the idea was to enhance competition, the changes weren't ideal at first. Teams felt that having the cars impounded made schedules more confusing and race day more hectic. NASCAR eventually addressed these problems and relaxed the rules to some degree.



­So, why exactly did NASCAR start impounding cars? What problems arose at the outset of implementing the impound rule? What restrictions are placed on crewmembers while the car is impounded? And, is there any way for a driver to bypass the one-setup rule? Read on to find out.


Reasons for Having Impound Races


­Though opinions on impound racing can be mixed, NASCAR officials put a lot of thought into its implementation. Rule changes are never quick and easy -- it takes time to explain and enforce the new rules, so NASCAR didn't formulate the impound rule without reason.


According to NASCAR, implementing impound races was a way to keep racing teams focused on the best setup for the race and to enhance competition. The idea was, and still is, to make racing a level-grounded sport, ensuring that teams with little money can compete with well-funded teams. Impound racing was seen as a way to curb expenses and save money. By impounding the car, a team is relieved of the need to have a qualifying setup and a race day setup.

It isn't unusual for a high-dollar team to have two complete setups. One setup is used to qualify, and then the team tears down that setup and rebuilds it for the race [source: Shinzawa]. Not only is this practice expensive, but some feel it takes away from the sport. When doing this, teams can build setups meant to make their car better at qualifying, but not necessarily ensure they will perform well at the race [source: Siska]. But with the impounding rule in force, the car is already built for the race when it goes through the qualification trials.

Now, let's look at the different types of restrictions that are placed on teams during impound races.

Impound Race Restrictions


Once a car has finished qualifying, NASCAR imposes impound restrictions. After the car has entered the garage, only two crewmembers are allowed to stay in the garage.


The only exception to the "no work once the car has been qualified" rule is if the crew is able to get prior approval from NASCAR, which is granted only under special circumstances.

On race day, NASCAR impound rules dictate that two crewmembers are allowed back in the garage, accompanied by a NASCAR official. Crewmembers may not:

  • Lift or jack up the car or any part of the car
  • Add water or pressure to the cooling system
  • Get inside the car
  • Adjust the sway bar, shocks or any bolts
  • Add fuel
  • Add oil
  • Add brake fluid
  • Adjust any body components including the spoiler or fenders
  • Remove air box
  • Change or add any components or spring inserts

Though some drivers and racing fans may feel the restrictions make impound races seem unfair, NASCAR does include some allowances in the rulebook. Next, up, you will learn what crew members can do after a qualifying race is completed.

Impound Race Allowances


After the qualifying race and inspection, the crewmembers are required to put the car into the garage while under the watchful eye of a NASCAR official. The two crewmembers that are permitted to remain in the garage are allowed to:


  • Turn off the master power switch and other electrical switches
  • Take out the radio
  • Check tire pressure
  • Place a cover over the car

When those actions are complete, the two crewmembers must leave the garage and close up shop. On race day, two crewmembers are allowed back into the garage so long as a NASCAR official accompanies them. The crewmembers are then able to:

  • Connect the oil heater (though any generators used must remain outside the garage)
  • Open the hood
  • Prime the oil system
  • Turn on the car
  • Remove the car from the garage
  • Open the oil cooler bypass valve if necessary
  • Start the engine
  • Close the hood
  • Check and set the tire pressure
  • Tighten the wheels
  • Put the radio back inside the car
  • Put in a water bottle
  • Remove or repair tape on front of car
  • Replace equipment batteries under NASCAR supervision

NASCAR also has strict limits on the amount of fuel that can be added to a car:

  • Two gallons of fuel can be added if the track is one mile long or less
  • If the track is one and a half miles long, three gallons of fuel can be added
  • If the track is more than one and a half miles, up to four gallons of fuel can be added
  • At no time can more than three crewmembers accompany a car to the fuel pumps -- and the crewmembers must be accompanied by a NASCAR official


If you would like to learn more about NASCAR racing and related topics, visit the links on the next page.

Related HowStuffWorks Articles


  • Shinzawa, Fluto. "Gentlemen, don't change your engines". The Boston Globe. (Accessed 01/12/09)
  • Siska, Ellen. "The ins and outs of impound races." (accessed 01/12/09)
  • Waltrip, Darrell. "New spoiler spoils good racing but impound rule works." Fox Sports. (accessed 01/12/09)
  • Warren, Hollis. "What Really Grinds My Gears: NASCAR's Impound Rule" (accessed 01/12/09)