Camber angle is the angle between a tilted wheel and the vertical plane.
The camber angle has influences on the tyres ability to generate lateral forces. A cambered rolling pneumatic wheel produces a lateral force in the direction of the tilt. This force is referred to as ‘Camber thrust’ when it occurs at zero slip angles (e.g. steering straight ahead).
Camber affects the aligning torque, making the wheels wanting to point straight ahead even when not rolling, due to distortion of the tyres footprint. The effect of this is rather small and tends to be cancelled with increasing slip angle.
Cambering the wheel also leads to an increase in the lateral force produced by the wheel when cornering. Camber changes as the wheel moves up and down. This change has a linear range and a non-linear range. Lateral forces increase in the linear range of the tyre. If the linear range is exceeded the additive effects of the camber inclination decreases, this effect is called Roll-off. Therefore the difference in lateral force when comparing a cambered wheel and a non-cambered wheel is small, around 5-10% at maximum slip angle (e.g. very hard cornering). The difference is much larger at zero degrees slip angle (e.g. straight ahead) due to the camber thrust.
The effects of cambering the tyre are bigger for a bias ply tyre than a radial ply tyre. For radial tyre the camber forces tends to fall of at camber angles above 5° while the maximum force due to camber for a bias ply racing tyre occurs at smaller angles.
Adjusting camber can have a dramatic effect on the cornering of your car. Optimum camber settings will result in more speed and ideal tyre wear. The ability to adjust the camber angle from 0° to about -4° will be very helpful during the testing of the car.
Camber is measured with a caster camber gauge and is usually easily adjusted with shims or adjustable upper a-arms. Always check the toe when making camber or caster adjustments. This should be done with the driver and any ballast.
The amount of static camber that you should run is a result of testing, tyre temperature measurements, front suspension geometry etc.
Setting the camber to 0° will minimizing the rolling resistance.
Poor Camber settings wil cause :
- Excessive tyre wear.
- Camber settings set to extremes can reduce the braking ability of the car.
Positive camber is defined as when the wheel is tilted outwards at the top relative to the car.
The term ‘Camber Out’ refers to the angle of the wheels when you are initially setting up the car.
This is normally done by removing the shock absorbers and placing the car on a raised block to allow the suspension to fully droop down.
The camber can then be measured by using such as a Camber Gauge and adjusted by whatever means the manufacturer of the car has provided.
Negative camber is defined as when the wheel is tilted inwards at the top relative to the car.
The term ‘Camber In’ refers to the angle that the wheels reach when the shock absorbers have been refitted and any raised block it has been sitting on has been removed. This angle may change with the driver inside and after the car has been run.
In theory this angle could be Neutral, Negative or Positive and so you should not automatically assume that Camber In means Negative Camber.
When the wheel is vertical with respect to the vehicle it is said to have ‘Neutral Camber’.
As a car turns around a bend the body rolls into the bend. Ideally the wheel would remain closer to vertical than the body. This is called ‘Camber Gain’.
The camber gain is to compensate for the lost of camber due to the roll angle during cornering.
It is often expressed as °Camber/1°Roll
Virtually any change in suspension design will result in a change in the camber gain ratio.
- The Biggest influence is angle of the upper A-arms in the side view.
- The angle of the lower A-arm plane in the front and side views, shows big influences on the camber gain during roll.
- If more camber gain is wanted the interaction of the angle of the upper A-arms and the angle of the lower A-arms in the side view is the combination that gives the biggest positive influence.
- The angle of the upper A-arms has the biggest negative influence when less camber gain is wanted.
- Setting this parameter to high value will decrease the amount of camber gain for the curve outer wheel and increase the amount of camber gain for the curve inner wheel.
- The camber change is not constant throughout the whole ride travel since the instant centre also moves with wheel travel.
- The reason for having a much larger camber gain at the rear axle is to have as big contact patch between the rear tyre and the ground during corner exits as possible.
“Camber Gain positive Roll” refers to the curve outer wheel measured at 0.5 degrees roll angle at contact patches and “Camber Gain negative Roll” refers to the curve inner wheel.