Race Car Suspension: Chassis Set-Up

For Performance Handling, Good Suspension Set-Up is a Must

Aug 30, 2009

All race cars have one thing in common: the suspension must be 'set-up' correctly to gain a competitive advantage.

The driver and the race engineer will work continuously at the race track to improve, or fine tune, the suspension settings. But what adjustments can the mechanics make, and how will these adjustments affect the car’s performance?

Base Line Settings

Although the suspension settings will be changed many times during a season (sometimes every session in F1, for instance), the team will have a starting point known as the base line settings. These settings will be supplied either by the manufacturer, in the case of a new car, or by the previous owner with a used car.

Suspension adjustment is required to set the geometry and weight distribution of any car. These adjustments may be for a particular race track, for performance enhancement, or driver preference. However, checking or setting the suspension must be undertaken in a set sequence due to the interaction of some of the adjustments – changing the tire pressures will alter the ride height, for instance.

To finish the procedure the mechanics must reattach the anti-roll-bars, reset the tire pressures to the cold settings (just prior to going on-track), and reset the damper settings.

The tire pressures are of particular importance because their settings affect so many of the other adjustments, and will affect (adversely) the car’s performance immediately the car goes on-track.

Roll Centers

Ride height adjustments will primarily affect the ground clearance and the aerodynamics. However, the ride height of a car has an effect on a number of other important geometrical considerations such as the roll centers, weight distribution, and the center of gravity.

Toe settings have a major effect on the car’s ability to enter a corner. Some race tracks will require the car to change direction quickly (street circuits, for instance) while other tracks will require the car to be very stable in long fast corners (super speedways, for instance). Often, a driver and engineer will make a compromise setting, especially if the track has both fast and slow corners. However, the engineer will be more concerned with the cars ability to take long fast corners as this is where most lap time reduction is possible.

More Caster for Fast Corners

Caster settings will affect the car’s ability to corner in much the same way as the toe settings. For instance, a lot of caster (more than 5 degrees positive) will be used on long fast corners where as, a small caster angle (less than 4.5 degrees) will be used on tight slow corners.

The race engineer and tire engineers will be interested in an even spread of temperature across the entire tire contact patch (sometimes known as the footprint). Adjusting the camber angle is one way of changing the heat spread. For example, leaning the top of a wheel toward the center line of the car will increase that particular tire’s inside temperature.

Perfectly Balanced Car

The corner weights of a race car are directly related to the total weight of the car and its aerodynamic down-force (or uplift). A perfectly balanced car will carry an even amount of weight on each tire; however, this is very rare. The engineer will attempt to get the cross weights to match, i.e., left front plus right rear matches right front to left rear.

Extracting the best performance from a race car will require many adjustments to the suspension. Each time a car goes on-track, the driver and engineer will study the logged data to see if a suspension adjustment will improve the lap times. And, as the team develops a car, the base line setting will be revised accordingly.

The copyright of the article Race Car Suspension: Chassis Set-Up in Auto Racing is owned by John Glimmerveen. Permission to republish Race Car Suspension: Chassis Set-Up in print or online must be granted by the author in writing.