camber angle

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Equation / Last modified by KurtHeckman on 2017/02/16 00:33
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KurtHeckman.camber angle
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The Camber Angle  calculator computes the camber angle (cA) based on the camber offset (o) and wheel or tire height (h). CamberA.pngTire Camber 

INSTRUCTION: Choose your preferred units and enter the following:

  • (o) horizontal offset
  • (h) height of the wheel or tire

Angle:The calculator returns the camber angle (cA) in degrees.  However, the can be automatically converted to other angle units via the pull-down menu.

To compute the tire offset from vertical using the camber angle, CLICK HERE.

The Math

The vertical tilt of a tire or wheel is called its camber.  The camber angle (C) is the measurement of that tilt.  This formula provides the angle based on height of the tire and offset from perfectly horizontal.  The use of a bubble level and a ruler can provide a rough measurement of these two lengths.

Positive and Negative Camber

The camber of a wheel can be positive or negative.  Positive camber is where the top of the wheel is leaning away from the axle.  Negative camber is where the top of the wheel is leaning toward the axle.  The diagram does not show the axle of the vehicle.  Assuming that the level was on the outside of the wheel and the axle was on the opposite side, the camber in the diagram would be negative.

Usage

Camber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering and suspension. If the top of the wheel is farther out than the bottom (that is, 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. α° = Approach angle:  ß°  = Departure angleApproach_and_departure_angle.png
 Break-over Angle (β )BreakOver.jpg
Camber Angle (Φ) 
Camber.png

Camber angle alters the handling qualities of a particular suspension design; in particular, negative camber improves grip when cornering. This is because it places the tire at a better angle to the road, transmitting the forces through the vertical plane of the tire rather than through a shear force across it. Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. The inside edge of the contact patch would begin to lift off of the ground if the tire had zero camber, reducing the area of the contact patch. This effect is compensated for by applying negative camber, 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 camber.

On the other hand, for maximum straight-line acceleration, the greatest traction will be attained when the camber angle is zero and the tread is flat on the road. 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 now become much more scientific with the use of computers, which can optimize all of the variables mathematically instead of relying on the designer's intuitive feel and experience. As a result, the handling of even low-priced automobiles has improved dramatically in recent years.

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 longitudinal centerline of the vehicle, for camber adjustment. Aftermarket plates with slots for strut mounts instead of just holes are available for most of the commonly modified models of cars.

Off-road vehicles such as agricultural tractors generally use positive camber. In such vehicles, the positive camber angle helps to 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.

See Also

Reference

  • Wikipedia - http://en.wikipedia.org/wiki/Camber_angle

Thanks to James Heckman for the technical description of tire camber.