Chassis Setup & Tuning (Drag Racing)
Slicks and performance street tires operate at generally higher pressures. Start with 18 - 20 pounds, and adjust up or down by 2 - 3 pounds at a time.
By optimizing starting line technique, you can substantially alter 60 foot times which will cut ET
Work with available traction and establish a baseline before tuning.
Experiment with shift points and launch technique until you have two consecutive runs within .05 seconds.
Car needs to launch straight and steer straight during gear changes.
Manipulate Weight transfer, when car wheel stands or squats
ET, Super Street, super gas doesn't need to be light weight. This will cost in durability and consistency. The benefit of a light car is it allows you to add weight where you want it.
Moving ballast is a significant tuning device.
A 4 link allows for extra tune ability, but is complex, a ladder bar setup is suitable for high nines. Ladder bars with a stick causes violent launches and produces more roll rotation during gear changes.
Shock absorbers are critical, they allow for chassis reaction no matter what type of suspension is in use.
Shock tuning (adjustable styles)
Front: 90/10 setting provides maximum weight transfer and traction.
Rear: 50/50 is for slick conditions, allowing the body to separate from the chassis and plant the tires. When track conditions are ideal, 70/30 will take some bite out of car.
Shocks are the best tuning device. Results of a shock change can be confirmed by other tuning changes.
Example: if your car goes quicker when you lighten the rear shock, the tires can take a harder hit; you can confirm this by taking out air in quarter pound increments to reduce the amount of support to the sidewalls.
If you keep taking adjustment out of the rear shocks, and the car keeps picking up, you'll run out of adjustment. Keep playing with tire pressure, ballast and launch RPM. Either add a lower gear to multiply the torque or raise the ladder bar, this will hit the tires harder. Remember though, to return air to your tires, lower the launch RPM to your baseline and stiffen the shocks so that you've made one change.
Car stiffness is important. Car will react better to tuning changes with a stiff chassis due to flexing caused by the reaction of the suspension. All four corners of the car must be braced and the engine and transmission should be secure within the car. This will allow you to tune the car with the shock absorbers and find out what needs to be done with the rest of the car.
To control pitch rotation at the front of the car, adjust shocks, adjust the amount of suspension travel, or add/remove ballast. At the rear you can raise or lower the ladder bar, move the instant center of car, or add/remove ballast.
When you launch so hard, the rims hit the ground and throw the rear end back up, you need to remove hook from the car. To remove hook, you need to stiffen the rebound adjustment so that the rear-end doesn't separate from the car so fast. With each stiffer setting the 60 foot times pick up and the car improves its reaction time. A bit more air in the tires, moving ballast forward, or lowering launch RPM would help also. Lower the ladder bar as a final adjustment. Rebound affects how the tires will get hit, bump relates to how the tires will react.
Next move to the front tires. If the car likes stiffer rebound, it will like less front travel to pull the tires out of the lights. If you limit travel to much, the car will dart when it hits bumps. You have to be the world’s best authority on how your car behaves. Use knowledgeable advice and experimentation with the laws of cause and effect.