Race Car Wheel Camber Angles
What Effect do Camber Angles Have on Suspension Performance?
Aug 25, 2009
To maximize the grip of a race car tire, the wheel must be at a certain angle – camber angle. However, this angle varies as the wheel and suspension move up and down in response to bumps and cornering forces.
In the early days of race car (and street car) suspension design, the wheels and tires would travel straight up and down (perpendicular) to the road. However, engineers soon realized that, as a car cornered, the body would roll. This roll was created by the tire’s resistance to slip against the chassis’ centrifugal force - generated by cornering.
As no two corners are the same, and the forces generated are never the same, a single camber angle would only work occasionally. The engineers needed a system of variable camber, the result: camber gain suspension.
Camber Gain
Modern race cars all have suspension that will generate additional camber as the wheel moves upwards in bump – the wheel gains camber. Each manufacturer will have deigned their car to optimize the available grip from the tires that will be used in a given race series; Formula One cars, for instance, all use Bridgestone tires. But each manufacturer will have a slightly different camber gain to complement their suspension characteristics.
The amounts of camber gain varies from car to car, team to team and even by the engineer’s philosophy on suspension set-up. Because current race cars have very little suspension travel (some cars have as little as15 mm’s of travel), particularly cars with high aero down-force, the amount of camber gain is also low. Generally, the camber gain for these types of car is in the order of 0.5 degrees of gain per 25 mm’s of travel.
Aerodynamics and Camber
Needless to say, aerodynamics play a major part in the set up of a race cars suspension. Pushing the bodywork down (such as when the wings develop down-force) compresses the suspension, and if the car has a camber gain curve, the camber angle will increase. This change in camber may be desirable during high speed cornering, but will be less so during heavy braking. It is the engineer’s responsibility to decide the best compromise.
Primarily, the engineer will be looking to generate an even amount of heat across the entire width of the tires. Heat in race car tires is generated by the coefficient of friction between the tires and the asphalt. If the temperature is even across the tire’s width, the engineer knows that the entire contact patch has been used. However, if, after a series of laps, the inside of a tire is cooler than the middle and the outside, the engineer may decide to increase the camber angle thereby putting more weight on the inside.
Tire Pressures
Tire pressures will play a large part in determining the correct camber angle, and can mislead the engineer if he ignores them. Also, the tire construction has a major effect on camber angle settings. For instance, radial tires require a far greater static camber angle than a cross-ply.
Camber angle optimization will also depend on the type of race track and, to a certain extent, driver preference. Testing prior to a race or qualifying session is invaluable to finding the correct camber angles; even prior race track experience may not be of any value if, for instance, the weather conditions are different.
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