Set Up a Race Car in the Shop Before Racing
Have you ever wanted to setup your race car with minimal effort? Here is an ordered procedure to help set the race car up the first time you try it. Make sure the driver is in the vehicle or the drivers’ weight is properly simulated using weight ballast and positioned for the following steps.
Steps
- Weigh the vehicle. Set it to the proper racing weight including all fluids such as fuel, coolant and oil (this weight is usually the minimum weight required by your home track).
- Determine the tire stagger to be used. Install a set of tires that will give you this setting with the proper air pressure in the tires. (Don’t overinflate or under inflate a tire to obtain proper stagger.) Set the air pressure in the tires to the pressure they will achieve at racing temperature. Notice that when the tires take on heat when racing they also tend to gain two pounds of air also. So, add two pounds to each tire once you set them to the pre race pressures.
- Set the ride height of the chassis. Pick a point between the wheels and as close to the wheels as possible. It is preferable to have the measuring point on a common surface such as a frame rail. If the ride height is not to specs, turn the weight jack bolts or shim the springs to achieve the specs. Also do the same for the rear also.
- Check the caster to make sure it is at the proper specification. Caster is the forward/aft (longitudinal) tilt of the steering spindle/McPherson strut. Remember a positive number means that the top of the spindle/McPherson strut leans to the rear of the vehicle. If the caster is not correct, then adjust it to the proper specification.
- Check the camber to make sure it is at the proper specification. Camber is the left/right (lateral) tilt of the steering spindle/McPherson strut. A positive number means that the top of the spindle/McPherson strut leans toward the outside of the vehicle. If the camber is not correct, then adjust it to the proper specification. When adjusting the upper a-arm of an a-arm type suspension, make sure to keep the front and rear a-arm pivot points equal to avoid changing the caster. In other words if the a-arm uses shims to adjust it, make sure to use or remove the same thickness of shim in the front adjust bolt that is used or removed in the rear adjust bolt. When adjusting a McPherson strut, make sure the strut upper mount moves laterally only and does not move longitudinally. After adjusting the caster and camber settings, it is a good idea to recheck them to make sure they are at the proper specs.
- Set the toe in/out of the front suspension. This is usually done with toe plates. A basic set up has the suspension toed out 1/8th of an inch.
- Adjust the cross weight to achieve the proper percentage of weight on the right front and left rear wheels. The easiest way to do this without changing the ride height is to determine the percentage of cross weight that is in the vehicle now. Multiply the percentage by the total vehicle weight. This is the amount of weight on the right front and left rear wheels. Determine the percentage of cross weight desired and multiply it times the total vehicle weight. This is the amount of weight desired on the right front and left rear wheels. Subtract the cross weight desired from the current cross weight (this is the weight difference and could be a negative number), then divide by 8. This number is how much weight on each wheel needs to be changed. Subtract this number from the left front wheel weight and adjust the weight jack accordingly. Add this number to the left rear wheel weight then adjust the weight jack. Subtract this number from the right rear wheel weight and change the weight jack. Finally add this number to the right front wheel weight and adjust the weight jack. An example of how this works is here. If your tracks rules don't allow weight jacks, there are spring rubbers and metal spring spacers that will raise and lower the ride heights of the car.
Tips
- Make sure the driver is in the vehicle or the drivers’ weight is properly simulated and positioned for all of the steps. The car is raced with a driver, if the driver's weight is not accounted for, then none of the adjustments will be correct. Sometimes it is not possible for the driver to be readily available when the vehicle is setup. If so, go through the setup the first time with the driver in the vehicle. When the driver gets out of the vehicle then record all of the weights and heights to be used later when the driver is not there.
Warnings
- Driving and/or working on a race vehicle is dangerous. Learn all the safety precautions needed and apply them to stay safe.
- When the vehicle is jacked up, make sure no one gets under any part of the vehicle. If someone must get under the vehicle, put jack stands or some kind of support under the vehicle's frame.
Things You'll Need
- Scales to weight the vehicle
- Caster/Camber gauge
- Tape Measure
