Another tidbit which many do not understand: setting the car up to race, you must set up and scale an asphalt race car with the driver's weight in the seat and the tires set to the Hot Air Pressures and fuel load as the car comes off the track! Not COLD AIR PRESSURE OR FULL FUEL LOAD!
We set all our angles for when the car is out at speed and tires have grown to what we set them at and expect them to grow to. Often guys will say the car changed. That change is because the car was set up at lower pressures and a full tank is not how we end. As fuel burns weight shifts forward and directly affects the handling.
Why Driver Weight Matters
- Weight distribution: The driver adds significant load, changing cross-weight, corner weights, and left-side percentages.
- Chassis balance: Sitting in the car shifts the center of gravity; scaling empty gives false readings.
- Alternative: If the driver is not present, use equivalent ballast weights (such as lead or sandbags) placed in the seat and footwell.
Why Tire Pressures Matter
- Ride height: Air pressure alters the height of the chassis; changing PSI later alters your ride heights and suspension geometry.
- Spring rate: Tires act as the first spring on the car; different pressures change how much a corner loads up on the scales.
- Consistency: Always set your air pressure to what it was at the end of the night!