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Wheel alignment sometimes referred to as breaking, or tracking is part of standard
automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarde ...
maintenance Maintenance may refer to: Biological science * Maintenance of an organism * Maintenance respiration Non-technical maintenance * Alimony, also called ''maintenance'' in British English * Champerty and maintenance, two related legal doct ...
that consists of adjusting the angles of wheels to the car manufacturer specifications. The purpose of these adjustments is to reduce
tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which t ...
wear and to ensure that vehicle travel is straight and true (without "pulling" to one side). Alignment angles can also be altered beyond the maker's specifications to obtain a specific handling characteristic. Motorsport and off-road applications may call for angles to be adjusted well beyond normal, for a variety of reasons.


Primary angles

The primary angles are the basic angle alignment of the wheels relative to each other and to the car body. These adjustments are the
camber Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...
,
caster A caster (or castor) is an undriven wheel that is designed to be attached to the bottom of a larger object (the "vehicle") to enable that object to be moved. Casters are used in numerous applications, including shopping carts, office chairs, ...
and
toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plan ...
. On some cars, not all of these can be adjusted on every wheel. These three parameters can be further categorized into front and rear (with no caster on the rear, typically not being steered wheels). In summary, the parameters are: * Front:
Caster A caster (or castor) is an undriven wheel that is designed to be attached to the bottom of a larger object (the "vehicle") to enable that object to be moved. Casters are used in numerous applications, including shopping carts, office chairs, ...
(left & right) * Front:
Camber Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...
(left & right) * Front:
Toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plan ...
(left, right & total) * Rear:
Camber Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...
(left & right) * Rear:
Toe Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plan ...
(left, right & total)


Secondary angles

The secondary angles include numerous other adjustments, such as: * SAI (Steering Axis Inclination) * Included angle * Toe out on turns * Maximum Turns * Toe curve change * Track width difference * Wheelbase difference * Front ride height * Rear ride height * Frame angle * Setback Setback is the difference between right side and left side
wheelbase In both road and rail vehicles, the wheelbase is the horizontal distance between the centers of the front and rear wheels. For road vehicles with more than two axles (e.g. some trucks), the wheelbase is the distance between the steering (front ...
length. It can also be measured as an angle. Setback less than the manufacturer specified tolerance (for example about 6mm) does not affect car handling. This is because when the vehicle is turning, one wheel is ahead of the other by several centimetres and therefore the setback is negligible. There are some car models with different factory setting for right and left side wheelbase length, for various design reasons. An off-spec setback may occur because of a collision or a difference between right and left caster. Rake is the difference between the front and rear ride heights, a positive number when the rear ride height is larger.


Measurement

A camera unit (sometimes called a "head") is attached to a specially designed clamp which holds on to a wheel. There are usually four camera units in a wheel alignment system (a camera unit for each wheel). The camera units communicate their physical positioning with respect to other camera units to a central computer which calculates and displays. Often with alignment equipment, these "heads" can be a large precision reflector. In this case, the alignment "tower" contains the cameras as well as arrays of LEDs. This system flashes one array of LEDs for each reflector whilst a camera centrally located in the LED array "looks for" an image of the reflectors patterned face. These cameras perform the same function as the other style of alignment equipment, yet alleviate numerous issues prone to relocating a heavy precision camera assembly on each vehicle serviced.


Camber

Camber is the angle which the vertical axis of the wheel makes with the vertical axis of the vehicle. This angle is very important for the cornering performance of the vehicles. Generally a Camber around 0.5-2 degrees is given on the vehicles. Depending upon wheel orientation, Camber can be of three types. 1. Positive Camber The Camber would be called positive when the top of the wheels lean outwards. Positive Camber is generally used in off-road vehicles. This is because, it improves the steering response and decreases the steering efforts required for turning the vehicle. Positive Camber is also provided in load carrying vehicles. This is because the heavy load on these vehicles cause outward leaning wheels to straighten up, improving the vehicle stability. 2. Zero Camber The vehicle is said to have zero Camber when the wheels stand perfectly straight on the ground. 3. Negative Camber Negative Camber is encountered when the top of the wheels lean inwards. Providing Negative Camber improves the cornering performance. When the vehicle turns on a corner, it performs a circular motion. Hence, it experiences equal and opposite centripetal & centrifugal forces. The centripetal force is experienced in the form of friction on tyres. The centrifugal force experienced by the car tries to throw it away from the turning center. This increases the normal reaction on the outer wheels. Due to increase in normal reaction, the frictional force on the outer tyres also increase. This friction acts as centripetal force and tries to bend the outer tires inwards. The tires get deformed due to bending and the contact area between the wheels and the ground decreases. This in turns decreases the frictional force between the outer tires and the ground causing the vehicle to drift during cornering. Hence a negative Camber is given to the vehicles. The negatively cambered wheels lean inwards. So during cornering when the frictional forces try to deform the outer wheels, they just simply get flat on ground increasing the friction with road surface.


Signs of a bad wheel alignment

* The vehicle pulls to one side * The steering wheel does not return to center * The steering wheel is off-center * Excessive tire wear in certain spots * Loose steering


See also

* Auto mechanic *
ASE Ase may refer to: * Ase, Nigeria, a town in Delta State, Nigeria * -ase, a suffix used for the names of enzymes * Aṣẹ, a West African philosophical concept * American Sign Language (ISO 639-3 code: ase) See also

* Åse (disambiguation) * ...
*
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 ...
* Car maintenance *
Tire balance Tire balance, also called tire unbalance or tire imbalance, describes the distribution of mass within an automobile tire or the entire wheel (including the rim) on which it is mounted. When the wheel rotates, asymmetries in its mass distribution ...
* Tire rotation


References

{{DEFAULTSORT:Wheel Alignment Motor vehicle maintenance Vehicle dynamics Alignment