First we will show you what these terms mean. Next, we will explain how these wheel positions influence the way the car handles. Try to imagine a vertical line through the centre of the tyre tread. Now imagine a line that runs through the steering axis. That is the axis around which the front wheels will turn when steering.
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The amount of toe-in or toe-out dialed into a given car is dependent on the compliance of the suspension and the desired handling characteristics. To improve ride quality, street cars are equipped with relatively soft rubber bushings at their suspension links, and thus the links move a fair amount when they are loaded. Race cars, in contrast, are fitted with steel spherical bearings or very hard urethane, metal or plastic bushings to provide optimum rigidity and control of suspension links.
Thus, a street car requires a greater static toe-in than does a race car, so as to avoid the condition wherein bushing compliance allows the wheels to assume a toe-out condition. Trad Morgans have a single bush at each links No change is necessary for racers.. BTW, designers have been using bushing compliance to advantage.
To maximize transient response, it is desirable to use a little toe-in at the rear to hasten the generation of slip angles and thus cornering forces in the rear tyres. By allowing a bit of compliance in the front lateral links of an A-arm type suspension, the rear axle will toe-in when the car enters a hard corner; on a straight-away where no cornering loads are present, the bushings remain undistorted and allow the toe to be set to an angle that enhances tyre wear and stability characteristics.
CASTOR Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. Positive caster tends to straighten the wheel when the vehicle is traveling forward, and thus is used to enhance straight-line stability. The mechanism that causes this tendency is clearly illustrated by the castoring front wheels of a shopping cart above.
The steering axis of a shopping cart wheel is set forward of where the wheel contacts the ground. As the cart is pushed forward, the steering axis pulls the wheel along, and since the wheel drags along the ground, it falls directly in line behind the steering axis.
The force that causes the wheel to follow the steering axis is proportional to the distance between the steering axis and the wheel-to-ground contact patch-the greater the distance, the greater the force. This distance is referred to as "trail.
If the steering axis were to be set vertical with this layout, the axis would be coincident with the tyre contact patch. The trail would be zero, and no castoring would be generated. Fortunately, it is possible to create castoring by tilting the steering axis in the positive direction. With such an arrangement, the steering axis intersects the ground at a point in front of the tyre contact patch, and thus the same effect as seen in the shopping cart casters is achieved.
The tilted steering axis has another important effect on suspension geometry. Since the wheel rotates about a tilted axis, the wheel gains camber as it is turned. This effect is best visualized by imagining the unrealistically extreme case where the steering axis would be horizontal as the steering wheel is turned, the road wheel would simply change camber rather than direction.
This effect causes the outside wheel in a turn to gain negative camber, while the inside wheel gains positive camber. These camber changes are generally favorable for cornering, although it is possible to overdo it. Like a shopping cart wheel left the trail created by the castoring of the steering axis pulls the wheels in line. Most cars are not particularly sensitive to caster settings and they cannot be changed on trad Morgans without the use of muscle as there is no adjustment feature built in.
Nevertheless, it is important to ensure that the caster is the same on both sides of the car to avoid the tendency to pull to one side.
While greater caster angles serve to improve straight-line stability, they also cause an increase in steering effort. Three to five degrees of positive caster is the typical range of settings. Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber see next page.
The cornering force that a tyre can develop is highly dependent on its angle relative to the road surface, and so wheel camber has a major effect on the road holding of a car. This can be a very difficult task, since, as the chassis rolls in a corner, the suspension must deflect vertically some distance. Since the wheel is connected to the chassis by several links which must rotate to allow for the wheel deflection, the wheel can be subject to large camber changes as the suspension moves up and down.
For this reason, the more the wheel must deflect from its static position, the more difficult it is to maintain an ideal camber angle. To maintain the ideal camber relative to the road, the suspension must be designed so that wheel camber relative to the chassis becomes increasingly negative as the suspension deflects upward. The illustration on the bottom of page 46 shows why this is so.
If the suspension were designed so as to maintain no camber change relative to the chassis, then body roll would induce positive camber of the wheel relative to the road. Thus, to negate the effect of body roll, the suspension must be designed so that it pulls in the top of the wheel i.
While maintaining the ideal camber angle throughout the suspension travel assures that the tyre is operating at peak efficiency, designers often configure the front suspensions of passenger cars so that the wheels gain positive camber as they are deflected upward. The purpose of such a design is to reduce the cornering power of the front end relative to the rear end, so that the car will understeer in steadily greater amounts up to the limit of adhesion.
Understeer is inherently a much safer and more stable condition than oversteer, and thus is preferable for cars intended for the public. Since most independent suspensions are designed so that the camber varies as the wheel moves up and down relative to the chassis, the camber angle that we set when we align the car is not typically what is seen when the car is in a corner.
The best way to determine the proper camber for competition is to measure the temperature profile across the tyre tread immediately after completing some hot laps. Thus, it may be advantageous to run extra negative camber to work the tyres up to temperature. CENTER When a suspension does not gain camber during deflection, this causes a severe positive camber condition when the car leans during cornering.
This can cause funky handling. Tuning dynamic camber angles is one of the black arts of suspension tuning. One calculates the angle of the kingpin from top to bootom and determines its inclination away fro the perpenticular. This angle was originally called kingpin inclination for all cars, but not all cars use kingpins any more. Morgans trads still do. This normally places the center line of the Steering axis nearer the center line of the tire-road contact area.
An alignment adjustment of this factor is not possible without force. Front suspension specifications If you take your car to an alignment shop, be sure to tell them you want to know the Camber angle, Castor angle and the kingpin inclination.
I suggest you do not tell them what the values are supposed to be at first. Let them tell you!
Below the FAQ section we also discuss and diagram the three most important wheel alignment terms; camber, caster, and toe. Wheel alignment changes the angle of your wheels and tires, and these angles affect vehicle handling, tire wear, tracking, and even gas mileage! Accelerated and abnormal tire wear Undesired Handling poor turn-in, understeer, oversteer, etc. Anytime any work is performed on the vehicles suspension, such as replacing tie rods, struts, bushings, etc. By owning your own wheel alignment gauge you will know if the vehicle actually needs adjusting, so no unnecessary trips or payments! Manufactures wheel alignment specifications are a compromise between handling, predictability, and gas mileage. Having your own wheel alignment tool or camber gauge makes checking your own alignment easy.
The amount of toe-in or toe-out dialed into a given car is dependent on the compliance of the suspension and the desired handling characteristics. To improve ride quality, street cars are equipped with relatively soft rubber bushings at their suspension links, and thus the links move a fair amount when they are loaded. Race cars, in contrast, are fitted with steel spherical bearings or very hard urethane, metal or plastic bushings to provide optimum rigidity and control of suspension links. Thus, a street car requires a greater static toe-in than does a race car, so as to avoid the condition wherein bushing compliance allows the wheels to assume a toe-out condition. Trad Morgans have a single bush at each links No change is necessary for racers.. BTW, designers have been using bushing compliance to advantage. To maximize transient response, it is desirable to use a little toe-in at the rear to hasten the generation of slip angles and thus cornering forces in the rear tyres.