Camber Angle, Caster Angle and Cross Caster

Camber Angle

Wheel angle relative to ground in front/rear view. Negative camber is defined as

the tops of the wheels closer together than the bottoms. Lateral grip of an

outside tire is optimized with -1° to -2° camber. 0° camber is optimum for

acceleration and braking. Excessive negative camber wears i/s of tire under

accelerate/braking and reduces grip. Not enough negative camber wears o/s of

tire under cornering and reduces grip

Caster Angle

Caster is the forward or rearward tilt of the steering axis center line, as viewed

from the side of the vehicle, and is measured in degrees from a vertical. It is a

directional control geometry angle that helps keep the vehicle moving straight

ahead. If the steering axis is tilted rearward, it is called "Positive Caster". A

forward tilt is called "Negative Caster ".

Suspension Group Helwan University Formula Student Team 2011

Chapter 2 8

Positive Caster increases stability at high speeds. Positive Caster also causes

increased steering effort at low speeds. Systems such as Servotronic help minimize

this negative effect. In addition to increased high speed stability, cornering is

enhanced and steering wheel returnability is improved by positive

Caster

Cross Caster

Cross Caster is the difference in the Caster measurement from left to right.

Excessive Cross Caster can cause the vehicle to pull to the side with the least

positive caster

Toe in/Toe out

Toe is the difference in length by which the wheels of each axle differ from each

other, front to rear, in the straight ahead position. The rear wheels are also subject

to toe measurement. Toe is measured at the center of the wheels from one wheel

rim to the other. When the distance is greater at the rear of the wheels, it is called

toe-in.

When the distance is greater at the front of the wheels, it is called toe-out.

Suspension Group Helwan University Formula Student Team 2011

Chapter 2 01

Rear wheel drive vehicles generally will have a small amount of toe-in at the front

wheels. This will allow the wheels to toe out when rolling to achieve a zero

running toe. Toe is measured in Degrees when using BMW specifications. Front

toe is adjustable on all BMW vehicles. Rear toe is only adjustable on some models.

Fig.2.4.:toe out

Center of Gravity {Height} (CG, {CGH}):

Location on the vehicle or sprung mass where all mass may be assumed to be

located. Longitudinal position defines f/r weight distribution. Height affects

roll moment. CGH are typically 9-11" for FSAE, and 20-25" for street.