What Is Camber & What’s Its Purpose?
Camber angle is the angle between the plane of a wheel and the vertical. It is described as positive when the top of the wheel leans outward and negative when the top of the wheel leans inward. Camber angle alters the handling characteristics of a suspension system.
There are 3 types of camber angle in particular:
Negative camber in general, improves handling when cornering. This works when a car is cornering, the lateral load transfer through the body causes the vehicle to roll. When the car encounters roll, it raises the inside contact patch of the outside wheel. This reduces overall grip. If the camber is set to negative then it has a smaller contact patch when it has zero roll but engages full contact patch as it corners rolling onto the full contact patch.
Neutral or Zero Camber
Neutral Camber angle is used in applications where hard cornering is not common such as road cars, drag racing, off – roading. When a tyre is in its neutral position, the full tyre contact patch is in full contact with the ground during zero roll situations. This is useful for acceleration purposes as it allows the entire contact patch of the tyre to be run at optimum slip angle to generate as much dynamic grip as possible for better acceleration and stability.
Positive camber is the most rarely used setting of the three camber settings. This is a specialised setting only used in a few forms of motorsport. It is only usually seen on a road car if there is damage to the suspension components. It is most commonly used in heavy load applications such as trucks where when the vehicle is empty, the tyres have positive camber so that when the vehicle is at its normal operating load the tyres then settle to a neutral camber position due to the camber gain of the system.
The Effects Of Camber
Camber force is a function of the tyre type, construction, shape, tread, pressure, load, tractive/braking effort and camber and slip angles. Observations and simple theory indicates that camber thrust of narrow bias ply tyres arises from a lateral distortion in the print. When a stationary tyre is pressed down onto the road at a camber angle, the centre plane of the print is curved. When the tyre is rolled at a zero slip angle, a point entering the print is constrained by the road to move though the print on a straight path defined by the motion. Therefore the road applies forces to the tyre which tend to remove the curvature of the stationary tyre print. The sum of these forces is the camber thrust. The diagram below shows how camber can cause forces through the tyre.
Camber Thrust And Slip Angle
It is possible to compare the lateral force produced by camber angle to that produced by slip angle. Because of the size and shape of the print distortion patterns, the lateral force generated in the linear range by one degree of slip angle is greater than that generated by one degree of camber.
For radial tyres the camber stiffness may be quite small since the lateral stiffness of the belt and the flexibility of the radial cord sidewall inhibit the kind of print distortion that gives rise to camber thrust. Such camber force as is generated may be due to distortion in the tread pattern or sidewall effects. For wide street and racing radial tyres the camber forces tend to fall off at camber angles above 5 degrees.