Front camber adjust

[johanp]

Good afternoon
How do you adjust the camber of the front wheels? Both front wheels on my Patrol have positive camber which cause that the outside of the tyres wear faster than the inside.
Do you adjust it with the 8 bolts (4 at top and 4 at bottom) at the bearings of the knuckle flange or do you adjust it with shims between the knuckle flange and the knuckle spindle? If it is done with the 8 bolts I can do it myself but if it needs shims I will have to get somebody to do it.
Who in Pretoria area is good with this type of work?
Thank you
Johan

[G-MAN]

Don't think caster is adjustable!

[Tinus lotz]

the guys at auto wiel are very competent and the have always helped me
i use the one at monovoni speak to james he is the owner there he gives great prices on tires too !!!
give him a call at 0828879740

[tour de frans]

Cannot adjust camber,but caster you can.

[Kagiso II]

Uhhhhhhhh... if yu adjust castor far enough then it mos becomes camber?? huh???
Soos die Generaal vir my gesê het - "Ekke moet kyk na my se polittieke - assik vêr genoeg regs murr sallik van links af inkom...
- - ik 'vstaan nou nog 'ie? Nog minner vannie castor en camber. (seker hukkô ik so bajja vanni pat af neek ?]

[Peter Connan]

Oom Mac if you adjust castor until it becomes camber, you won't be able to turn, just waggle your wheels.

[tour de frans]

JA Oom mac,net as jy die stuur draai,dan kom die "toe out around corners ook in".Om n kar caster te gee maak hom baie meer rybaar op die pad.En onthou,moetnie werk volgens wat die boek se oor die wielsporing ,as jou kar groter wiele het of gelig is nie.Dit beteken niks!

[Grant]

Great explanation off the net


THE EFFECTS OF CASTER

Caster is the angle to which the steering pivot axis is tilted forward or rearward from vertical, as viewed from the side. If the pivot axis is tilted backward (that is, the top pivot is positioned farther rearward than the bottom pivot), then the caster is positive; if it's tilted forward, then the caster is negative.

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 castering front wheels of a shopping cart. 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."

Due to many design considerations, it is desirable to have the steering axis of a car's wheel right at the wheel hub. If the steering axis were to be set vertical with this layout, the axis would be coincident with the tire contact patch. The trail would be zero, and no castering would be generated. The wheel would be essentially free to spin about the patch (actually, the tire itself generates a bit of a castering effect due to a phenomenon known as "pneumatic trail," but this effect is much smaller than that created by mechanical castering, so we'll ignore it here). Fortunately, it is possible to create castering 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 tire 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.

Most cars are not particularly sensitive to caster settings. 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, with lower angles being used on heavier vehicles to keep the steering effort reasonable.








WHAT IS CAMBER?

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 tire 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. It's interesting to note that a tire develops its maximum cornering force at a small negative camber angle, typically around neg. 1/2 degree. This fact is due to the contribution of camber thrust, which is an additional lateral force generated by elastic deformation as the tread rubber pulls through the tire/road interface (the contact patch).

To optimize a tire's performance in a corner, it's the job of the suspension designer to assume that the tire is always operating at a slightly negative camber angle. 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. Thus, the relatively large wheel travel and soft roll stiffness needed to provide a smooth ride in passenger cars presents a difficult design challenge, while the small wheel travel and high roll stiffness inherent in racing cars reduces the engineer's headaches.

It's important to draw the distinction between camber relative to the road, and camber relative to the chassis. 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.e., gains negative camber) as it is deflected upwards.

While maintaining the ideal camber angle throughout the suspension travel assures that the tire 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. Nevertheless, it's really the only reference we have to make camber adjustments. For competition, it's necessary to set the camber under the static condition, test the car, then alter the static setting in the direction that is indicated by the test results.

The best way to determine the proper camber for competition is to measure the temperature profile across the tire tread immediately after completing some hot laps. In general, it's desirable to have the inboard edge of the tire slightly hotter than the outboard edge. However, it's far more important to ensure that the tire is up to its proper operating temperature than it is to have an "ideal" temperature profile. Thus, it may be advantageous to run extra negative camber to work the tires up to temperature.

[Peter Connan]

Good post Grant, although I would like to make a couple of small points:

Camber:
On cars with live axles, like the Patrol, this is generally not adjustable, but is a function of the position of the hub bearings in the axle casing, thus it is set by the designer. However wear or maladjustment of these bearings (preload) may cause a change in camber angle (coupled with play where there shouldn't be any play). Also, with a live axle or DeDion Tube, the camber will remain basically the same independent of body roll and cornering.

Caster:
In a Patrol, the caster is affected by the suspension lift or sag, and suspension lift reduces the caster angle quite drastically. The standard angle for a Y60/GQ wagon is between 2 and 3 degrees. A lift of 50mm will reduce this angle by 3.6degrees, thus you end with positive caster if you do not take steps to correct it. This will probably cause the car to veer all over the place. I only know of four methods to "adjust" or correct the caster angle on a Patrol after a lift, which are listed here in order of cost:
1) Fit caster correction bushes (note that this reduces the front suspension's ability to twist).
2) Fit drop-boxes (keeps flex the same but may catch on rough trails).
3) Fit Superior Engineering's front control arms with the correct brackets (improves flex (apparently by up to 40% if the shocks can keep pace), but may increase axle tramp).
4) Fit X-link front suspension (increases flex hugely but requires welding on the axle tube).

[Kagiso II]

GOLD MEDAL For the last 2 posts - thanx many millions Grant & Peter- now I now something I never ever before even thought about

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