{{Multiple image, direction=vertical, align=image1=BobbyLabonteCarApril2007.jpg, image2=Carl EdwardsTexasMotorSpeedway.jpg, width=265, caption1=At rest the air dam (red) of a car appears several inches above the ground., caption2=At full speed the air dam appears much closer to the ground.
Coil bind is a style of setup used in various levels of
NASCAR
The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
racing
In sport, racing is a competition of speed, in which competitors try to complete a given task in the shortest amount of time. Typically this involves traversing some distance, but it can be any other task involving speed to reach a specific goa ...
. Coil bind setups utilize very soft front springs and very stiff rear springs to control the pitch attitude of the body. This is in contrast with conventional setups which place the stiffer springs at the front of the car for superior mechanical grip, that is grip via the
vehicle suspension
Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding/ handling and ride ...
and
tires
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
. Coil bind uses
aerodynamics
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
to produce grip.
As a car approaches the end of a straightaway, the
downforce
Downforce is a downwards lift force created by the aerodynamic features of a vehicle. If the vehicle is a car, the purpose of downforce is to allow the car to travel faster by increasing the vertical force on the tires, thus creating more grip ...
generated by the body of the car should increase the
sprung weight
Sprung mass (or sprung weight), in a vehicle with a suspension, such as an automobile, motorcycle, or a tank, is the portion of the vehicle's total mass that is supported by the suspension, including in most applications approximately half of the ...
until the
coil spring
A selection of conical coil springs
The most common type of spring is the coil spring, which is made out of a long piece of metal that is wound around itself.
Coil springs were in use in Roman times, evidence of this can be found in bronze Fib ...
s compress until they bind and the suspension can no longer
travel
Travel is the movement of people between distant geographical locations. Travel can be done by foot, bicycle, automobile, train, boat, bus, airplane, ship or other means, with or without luggage, and can be one way or round trip. Travel c ...
(hence the name).NASCAR.com Article about coil bind The goal of coil bind is to keep the air dam (or splitter if applicable) at the front of the car as low to the ground as possible to create an area of
low pressure
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible ...
under the car. The result is similar to ground effects. Under braking,
weight transfer
Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects:
*the change in load borne by different wheels of even perfectly rigid vehicles during acceleration
*the change in center of mas ...
causes more weight to shift forward as the vehicle decelerates. This helps to maintain the low-pressure area below the car by keeping the front of the car low to the ground. While coil bind setups do yield faster lap times, the cars are more sensitive to
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
generated by nearby cars.
See also
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Car handling
Automobile handling and vehicle handling are descriptions of the way a wheeled vehicle responds and reacts to the inputs of a driver, as well as how it moves along a track or road. It is commonly judged by how a vehicle performs particularly durin ...
*
Racing setup In motorsport, the racing setup, car setup or vehicle setup is the set of adjustments made to the vehicle in order to optimize its behaviour (performance, handling, reliability, etc.) for specific conditions. Vehicle setups are variable for a vari ...
*
Vehicle dynamics
For motorized vehicles, such as automobiles, aircraft, and watercraft, vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air ...