Spoiler (automotive): Wikis


Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.


From Wikipedia, the free encyclopedia

A spoiler is an automotive aerodynamic device whose intended design function is to 'spoil' unfavorable air movement across a body of a vehicle in motion. Spoilers on the front of a vehicle are often called air dams, because in addition to directing air flow they also reduce the amount of air flowing underneath the vehicle which reduces aerodynamic lift. Spoilers are often fitted to race and high-performance sports cars, although they have become common on passenger vehicles as well. Some spoilers are added to cars primarily for styling purposes and have either little aerodynamic benefit or even make the aerodynamics worse.

Spoilers for automobiles are often incorrectly confused with, or the term used interchangeably with, wings. Automotive wings are devices whose intended design is to generate downforce as air passes around them, not simply disrupt existing airflow patterns.

The Plymouth Superbird is famous for its giant rear spoiler.



Spoilers function by disrupting or diffusing the airflow passing over and around a moving vehicle as it passes over the vehicle. This diffusion is accomplished by increasing amounts of turbulence flowing over the shape, "spoiling" the laminar flow and providing a cushion for the laminar boundary layer. Often spoilers are added solely for appearance with no thought towards practical purpose.

Passenger vehicles

This Toyota MR2 sports car has a factory-installed rear spoiler.

The main design goal of a spoiler in passenger vehicles is to reduce drag and increase fuel efficiency. While many often imitate wings and airfoils, these serve mostly decorative purposes. Passenger vehicles can be equipped with front and rear spoilers. Front spoilers, found beneath the bumper, are mainly used to direct air flow away from the tires to the underbody where the drag coefficient is less. Rear spoilers, which modify the transition in shape between the roof and the rear and the trunk and the rear, act to minimize the turbulence at the rear of the vehicle.

Sports cars are most commonly seen with front and rear spoilers. Even though these vehicles typically have a more rigid chassis and a stiffer suspension to aid in high speed maneuverability, a spoiler can still be beneficial. This is because many vehicles have a fairly steep downward angle going from the rear edge of the roof down to the trunk or tail of the car. At high speeds, air flowing across the roof tumbles over this edge, causing air flow separation. The flow of air becomes turbulent and a low-pressure zone is created, increasing drag and instability (see Bernoulli effect). Adding a rear spoiler makes the air "see" a longer, gentler slope from the roof to the spoiler, which helps to delay flow separation. This decreases drag, increases fuel economy, and helps keep the rear window clean.

Due to their association with racing, spoilers are often viewed as "sporty" by consumers.

Material types

Spoilers are usually made of:

  • ABS plastic — Most original equipment manufacturers create spoilers produced by casting ABS plastic with various admixtures, which bring in plasticity to this inexpensive but fragile material. Frailness is a main disadvantage of plastic, which increases with product age and is caused by the evaporation of volatile phenols.
  • Fiberglass — Used in car parts production due to the low cost of the manufacturing process. Fiberglass spoilers consist of fiberglass filler fastened with synthetic tar. Fiberglass is sufficiently durable and workable, but has become unprofitable for large scale production.
  • Silicon — More recently, many auto accessory manufacturers are using silicon-organic polymers. The main benefit of this material is its phenomenal plasticity. Silicon possesses extra high thermal characteristics and provides a longer product lifetime.
  • Carbonfiberglass based on carbon fiber is the youngest material on the automotive aftermarket. Carbon is light weight, durable, but also a very expensive material. Unlike ordinary fiberglass, solidification of the connecting tar takes place in a pressure chamber using high temperatures. Due to the very large amount of waste during the manufacturing process, large scale producers cannot widely use carbon fiber in automobile parts production currently.[1][2]

Other vehicles

Heavy trucks, like long haul tractors, may also have a spoiler dome on the top of the cab in order to lessen drag caused from air resistance from the trailer it's towing, which may be taller than the cab and provide a very non-aerodynamic effect. These spoilers primarily increase fuel economy instead of improving handling, however.

Trains may use spoilers to induce drag (like an air brake). A new prototype Japanese high-speed train, the Fastech 360 is designed to reach speeds of 250 mph. Its nose is specifically designed to spoil a wind effect associated with passing through tunnels, and it can deploy 'ears' which act to slow the train in case of emergency by increasing its drag.

Some modern race cars employ a situational spoiler called a roof flap. These roof flaps deploy when the body of the car is rotated so it is traveling in reverse. The car will then generate lift instead of countering it. The roof flaps deploy because they are recessed into a pocket in the roof. The low pressure above this pocket will cause the flaps to deploy, and counteract some of the lift generated by the car.


Related terms


Got something to say? Make a comment.
Your name
Your email address