Lecture 2 – Tyres
F=MA – Acceleration, Braking, Cornering
A= v^2/r – Centripetal acceleration
The Tyre is the single most important part of a race car
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Only link to the road/racing surface, only real feedback to the driver
Going Faster = Maximising use of tyre
The goal of race car engineering is to make the best use of your tyres
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Driver training, data acquisition, brakes, suspension, aerodynamics,
engine and drivetrain all used to maximise the usefulness of the tyre.
Bias Ply Tyre – Zenith angle between 30 and 40 degrees
Radial Tyre – Zenith angle between 15 and 35 degrees
Ff = Cf * Fv
CF – Coefficient of friction
Bigger CF means more grip
Three parts to friction
1. Adhesion – the stickiness of the rubber, higher temperature
rubber becomes stickier/glue like
2. Deformation – the tyre structure deforms and provides grip (see
diagram)
3. Tearing/Wear – the tyres particles break apart the energy used to
do this provides grip, the force to pull these particles apart.
Slip Ration Equation
Slip Angle – the angle between the tyre heading
and the direction of motion
Longitudinal and Lateral Grip
Cannot have ideal grip in all directions at once,
instead we have a tyre friction eclipse
As a tyres load increases its coefficient of friction
decreases
Many setup changes affect the car tyre to tyre
loading; springs, dampers, ARB, Aero.
Camber Thrust
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Ideal lateral grip usually at some negative camber
Ideal longitudinal grip at 0 camber
Fundamental trade off
Temperature Sensitivity
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Optimum temperature for maximum grip, too cold not enough, too
hot not enough
Modulus of elasticity (resistance to deformation) of rubber changes
with temperature affects cornering stiffness