Camber angle

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The 1960 Milliken MX1 Camber Car has a large negative camber MillikenMX1CamberCar1960.jpg
The 1960 Milliken MX1 Camber Car has a large negative camber

Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the creation of steering and suspension. If the top of the wheel is farther out than the bottom (that is, tilted away from the axle), it is called positive camber; if the bottom of the wheel is farther out than the top, it is called negative camber.

Contents

Effect on handling

Negative front wheel camber is used in drift cars to improve their handling Kunmadaras Motorsport 2021. szeptember 19. JM (147).jpg
Negative front wheel camber is used in drift cars to improve their handling

Camber angle alters the handling qualities of some suspension designs; in particular, negative camber improves grip in corners especially with a short long arms suspension. This is because it places the tire at a better angle to the road, transmitting the centrifugal forces through the vertical plane of the tire rather than through a shear force across it. The centrifugal (outwards) force is compensated for by applying negative camber, which turns the contact surface of the tire outwards to match, maximizing the contact patch area. Note that this is only true for the outside tire during the turn; the inside tire would benefit most from positive camberagain, only with a short long arms system. However, due to the weight transfer inherent while turning, the outside wheels bear more of the force of turning and negative camber will improve handling overall. Caster angle will also compensate for this to a degree, as the top of the outside tire will tilt slightly inward, and the inner tire will respectively tilt outward. However, any camber affects the contact patch of the tire while driving in a straight line. Zero camber gives the best traction as it maximises the contact patch between the road and the tires and puts the tire tread flat on the road. Therefore excessive camber impairs straight driving in rain and snow and when accelerating hard.

Proper management of camber angle is a major factor in suspension design, and must incorporate not only idealized geometric models, but also real-life behavior of the components; flex, distortion, elasticity, etc. What was once an art has become much more scientific with the use of computers, which can optimize all of the variables mathematically instead of relying on the designer's intuition and experience. As a result, the handling of even low-priced automobiles has improved dramatically. Heavy-duty vehicles, such as tractors, trucks, etc., tend to have more positive camber angle, so that when they are loaded and the whole vehicle lowers, the wheels are almost vertical.

Adjustability

In cars with double wishbone suspensions, camber angle may be fixed or adjustable, but in MacPherson strut suspensions, it is normally fixed. The elimination of an available camber adjustment may reduce maintenance requirements, but if the car is lowered by use of shortened springs, the camber angle will change. Excessive camber angle can lead to increased tire wear and impaired handling. Significant suspension modifications may correspondingly require that the upper control arm or strut mounting points be altered to allow for some inward or outward movement, relative to the longitudinal centerline of the vehicle, for camber adjustment. With aftermarket plates containing slots for strut mounts instead of merely holes, this allows the entire shock absorber to be able to move back and forth, allowing for fine-tuning the camber of a vehicle. These plates are available for most of the commonly modified models of cars. Some aftermarket coilovers come with built-in camber plates already in place, and there are certain other aftermarket solutions which allow the modification of the camber angle of the wheels. [1] Camber bolts with eccentrics allow adjustable camber on some vehicles. These bolts feature large washers that are either eccentric or offset. If the original-equipment bolts are replaced with eccentric ones, then the adjustment will engender a change of up to two degrees. Control arms (or A-arms) with adjustable ball joints represent another avenue for allowing side-by-side adjustability. With these control arms installed, tire camber can effectively be changed by simply moving the tires. After that, one tightens the bolts in order to lock the ball joint in the desired position. Yet another aftermarket solution for changing the camber angle is via control rods of adjustable length. However, this solution is only amenable to vehicles which employ control rods, not A-arms. Because control rods (in vehicles so equipped) are responsible for locating the suspension points and keeping them in place, changing the overall length of the rods influences the camber angle.

Camber in uneven terrain

Tatra Trucks have quite acute positive camber due to their chassis design, which incorporates a central-tube and swing axles, as seen on this Tatra 815 crane truck. Autojerab tatra 815.jpg
Tatra Trucks have quite acute positive camber due to their chassis design, which incorporates a central-tube and swing axles, as seen on this Tatra 815 crane truck.

Off-road vehicles such as agricultural tractors generally use positive camber. In such vehicles, the positive camber angle helps achieve a lower steering effort. Also, some single-engined general-aviation aircraft that are primarily meant to operate from unimproved surfaces, such as bush planes and cropdusters, have their taildragger gear's main wheels equipped with positive-cambered main wheels to better handle the deflection of the landing gear, as the aircraft settles on rough, unpaved airstrips.

Camber wear

If excessive cambereither positive or negativeis applied, the vehicle's tires will wear unevenly, a condition known as "camber wear".

A suspension with excessive negative camber places more load on the inboard shoulder of the tire, causing the inboard shoulder to wear out quicker than the outboard shoulder. Depending on suspension design, a minor negative camber setting may slightly improve tire wear, as during turns the vehicle's center of gravity shifts toward the outside of the outer wheel. On a vehicle with zero camber this places load on the outboard shoulder of the tire, causing uneven wear over time. A small negative camber angle allows this load to be more evenly distributed across the tread.

Positive camber will generally place more load on the outboard shoulder, causing it to wear more quickly than the inboard shoulder. This is among the many reasons vehicles are not typically aligned with extreme positive or negative camber settings from the factory.

Stance cars

Negative camber Washington Auto Show 2023 Extreme Negative Camber car.jpg
Negative camber

Negative camber was primarily used in motor sports due to the traction increase around turns. However, it eventually became popular to use negative camber in order to be able to lower a car and fit wheels on it which would not normally fit in the fender wells. Cars with these modifications eventually were given the name "stance cars". It is difficult to pinpoint when exactly this trend began, although it became mainstream in the 1970s with the bōsōzoku cars coming out of Japan. This trend began with the intent of making street cars look more like race cars by lowering their suspension and adding a little negative camber. As time went by, such cars were being customarily lowered more and more, as well as having much more negative camber than before. With the growing of stance-car culture, it also attracted criticism, since extreme amounts of negative camber and minimal ground clearance can makes these cars rather impractical. Accordingly they occasionally became the subject of ridicule from other car enthusiasts, who enjoyed sharing videos of such cars getting stuck on speed bumps.

Notes

1. ^ While nearly all automobiles now use "negative camber" on all four wheels, this convention dates from a time period when positive camber was more common.

See also

Related Research Articles

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<span class="mw-page-title-main">Steering</span> The control of the direction of motion of vehicles and other objects

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<span class="mw-page-title-main">Car suspension</span> Suspension system for a vehicle

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<span class="mw-page-title-main">Independent suspension</span> Vehicle suspension in which each wheel is suspended independently

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<span class="mw-page-title-main">Double wishbone suspension</span> Automotive independent suspension design

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<span class="mw-page-title-main">Caster angle</span> The angle between the vertical axis and the steering axis of a steered wheel, in side view

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<span class="mw-page-title-main">Toe (automotive)</span> Installing wheels on a vehicle so that the wheels faces are not completely parallel

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<span class="mw-page-title-main">Coilover</span> Automobile suspension device

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<span class="mw-page-title-main">Ride height</span>

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<span class="mw-page-title-main">Control arm</span> Element on a suspension machine

In automotive suspension, a control arm, also known as an A-arm, is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel. In simple terms, it governs a wheel's vertical travel, allowing it to move up or down when driving over bumps, into potholes, or otherwise reacting to the irregularities of a road surface. Most control arms form the lower link of a suspension. Control arms play a crucial role in the suspension system of a vehicle. They help to keep the wheels aligned and maintain proper tire contact with the road, which is essential for safety and stability.

<span class="mw-page-title-main">Beam axle</span> Automobile mechanism

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<span class="mw-page-title-main">Bump steer</span>

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<span class="mw-page-title-main">Jaguar independent rear suspension</span> Common component of a number of Jaguar production cars since 1961

Jaguar's independent rear suspension (IRS) unit has been a common component of a number of Jaguar production cars since 1961, passing through two major changes of configuration up to 2006 and last used in the Jaguar XK8 and Aston Martin DB7. This article concentrates on the first generation Jaguar IRS, which firmly established the marque's reputation for suspension sophistication, combining as it did smooth ride with excellent roadholding and low levels of noise, vibration, and harshness (NVH). The two generations overlap in time due to their being used in both full size and sports models that were updated at different times.

<span class="mw-page-title-main">Stance (vehicle)</span> Auto term for positioning of a vehicle

The stance of a vehicle is determined by its suspension height and the fitment of the wheels in the fender arches. It may refer to any vehicle, including sports cars, pickup trucks and off-road vehicles, however it is mostly associated with lowered sports cars, sedans, hatchbacks, vans and other body styles of passenger cars. The term stance is most commonly associated with the stanced car subculture, a style of modifying cars which emphasizes lowering cars, typically with either coilovers or air suspension, and often adding negative camber to the wheels to achieve the "stanced" look. The main parameters of the vehicle's stance are suspension height and position of the wheels. Suspension height usually depends on the suspension components while wheel position usually depends on the rim size and offset. Tire fitment also plays a big role from both visual and functional perspective.

References

  1. "Camber angle for racing cars: Explanation".