Log in

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 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 even 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.

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.[citation needed] Often spoilers are added solely for appearance with no thought towards practical purpose.

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.