Two of the most basic, but...
Two of the most basic, but also most important, settings on the front of the car are caster and camber. These two conditions affect the driver's feel when steering the car through the turns as well as the amount of footprint the tire will ultimately have.
Caster and camber settings are set relative to the type of car and the design of the racetrack. When you determine the correct settings for each, you need to maintain those settings. We will discuss what affects caster and camber in our racecars as well as how to properly measure them.
It is important to know how to properly measure for the amount of caster and camber in your racecar. All teams need to learn the proper procedure for determining the amount of each that exists in the front-end geometry of their racecars.
Caster is a design condition that, in addition to the spindle kingpin angle, serves to cause a wheel to want to track straight ahead. A common example is a bicycle front-wheel and fork assembly. The tube that the handlebars are mounted to is mounted in a set of bearings above the fork. From a side view, this tube is angled so that the bottom bearing is ahead of the top bearing. If we turn the front wheel to 90 degrees from the direction of travel, it will want to return to straight ahead by the effect of caster. The same effect is present in the front-wheel assemblies of our racecar.
Positive caster in the front-wheel...
Positive caster in the front-wheel assembly is created when the ball joints are offset, from a side view, so that the upper ball joint is farther to the rear of the car than the bottom ball joint. The degree of caster is related to the angle in degrees that a line through the ball joints forms from a vertical line.
What Caster Does
To ease the amount of effort it takes to turn the wheel in our race cars, we introduce caster split into the design. Split means that we set different caster amounts into each wheel assembly so that the car will want to turn to the left and thereby reduce the amount of effort it takes for the driver to hold the steering wheel when negotiating the turns.
Proper split for circle track racing means that the left-front wheel will have less positive caster than the right-front wheel. In some cases, teams have been known to set negative caster in the LF wheel and positive caster in the RF wheel.
To measure caster in each wheel, we use a caster/camber gauge. This tool attaches to the wheel hub. To check the amount of caster, we need to follow these instructions:
1. Attach the caster/camber gauge to the right-front wheel hub first.
It is a good idea to use turn...
It is a good idea to use turn plates in order to know exactly when you have turned the wheel 20 degrees, the proper amount for caster measurements according to SAE standards.
2. Turn the steering wheel to the right so that the right-front wheel has turned exactly 20 degrees.
3. For a manual gauge, level the gauge and set the adjustable caster bubble vial so that the bubble is at the zero mark on the caster side of the tool. For a digital gauge, set the tool to caster and zero the display.
4. Turn the steering wheel to the left so that the right-front wheel is turned past straight ahead and ends up left of straight ahead by 20 degrees.
5. Again, level the gauge and then note the location of the bubble on the scale of the manual gauge and record the amount of caster in the right-front wheel. For a digital gauge, level the gauge and read the display.
6. While the wheels are still turned left 20 degrees, remove the caster/camber gauge and place it onto the left-front wheel hub.
7. Level the gauge and set the bubble on the caster gauge to zero or set the digital display to zero.
8. Turn the steering wheel to the right past straight ahead until the LF wheel is turned 20 degrees to the right of straight ahead.
9. Level the gauge and read the bubble scale or display to know how much caster is in the LF wheel.
Set the bubble at zero on...
Set the bubble at zero on the caster side of the gauge with the wheel turned to the right 20 degrees for the RF wheel. Some teams use one edge of the bubble so that reading the angle is more accurate than trying to estimate the center of the bubble.
For a digital gauge, turn...
For a digital gauge, turn the wheels to the right so that they turn 20 degrees. Then, level the gauge and push the "zero" button to set zero in the display.
Turn the wheel past 0 degrees...
Turn the wheel past 0 degrees on the turn plates and go past that to 20 degrees left turn. Again, level the gauge and read the amount of caster in the display. Repeat for the left-front wheel, only in reverse order, turning left first.