Arm Angles The angle of the control arms has a large effect on camber change. The upper control arms affect camber change much more than the lower control arms. The smaller the angles (from horizontal) that the upper control arms have, the less camber change that will result from chassis dive. A chassis with less upper control arm angle will also have more camber change resulting from chassis roll.
The static left-front wheel...
The static left-front wheel camber used on ultra-high banked tracks isusually very high, in the 4-5 degree range, due to the extreme amount ofcamber loss due to chassis dive. These cars roll very little andcompress up to 4 inches or more at tracks like Daytona. There are somevery high-banked dirt and asphalt short tracks where a similar situationexists.
The opposite is true of higher angled upper control arms. The degree of angle we have in the upper control arms will influence the amount of camber change. Optimum control arm angles are determined mostly by using the correct dive and roll numbers and simulating the attitude of the car at mid-turn. We can do this mechanically or with the use of a computer program.
The left wheel will always lose two degrees of camber or more due to the roll effect. There is no known design that will help this camber change and still have us maintain a correct moment center design. To even approach this goal, the left upper control arm would have to have around 45 degrees of reverse angle with the chassis mount higher than the ball joint. We would never do this to our race car, so we live with the left wheel camber change.
Spindle Heights The spindle height affects the amount of camber change in our race cars. The height of the spindle is the measured distance between the centers of rotation of the upper and lower ball joints. Spindles come in many different heights. What is generally true is that the greater the spindle height, the less camber change that will result from dive and roll.
It is reasonably easy to understand this. If the upper ball joint moves laterally one inch, the spindle will change its angle more with a 10-inch spindle than with a 12-inch spindle. The greater the distance between ball joints, the less angle that is produced with the same amount of upper ball joint movement, therefore, the less degree of camber change.
(above & right) The camber...
(above & right) The camber change characteristics can be adjusted by changing the angleof the upper-control arms. We usually adjust the right upper control armangle until we get zero change in camber after dive and roll. We thenadjust the location of the moment center, using the angle of the leftupper control arm. Upper-control-arm mounting plates using offset-holeslugs make changes to arm angles fast and easy. Slotted plates foradjusting caster do not allow angle changes. Control arm shafts withslots for caster adjustment are available to use in conjunction with theslugged upper plates.
How do we put all of this information together into a design for a front end that we can use? Let's draw some simple conclusions.
As a rule, a flatter track will produce more of a chassis roll angle with less chassis dive. As the track banking angle increases, the amount of chassis roll decreases and the amount of chassis dive increases due to more downforce effect. The overall goal here is to produce the least combined camber change in each wheel, and especially the right front wheel, for each type of racetrack.
High Left-Front Camber Change The left-front (LF) wheel will always lose most of its positive camber as the car negotiates the turn. We need to end up with some amount of positive angle in the LF wheel after dive and roll. If the chassis rolled three degrees and the LF suspension did not travel at all, the camber change would be three degrees. We can simulate that at the shop by dropping the right side of the car to create 3 degrees of roll. The LF wheel will lose 3 degrees of camber.