Race Car Ride Heights
From F1 to NASCAR, Ride Heights are Critical
Colin Chapman pioneered the design of race cars that took advantage of the aero gains associated with traveling close the ground. In the early days of aero down-force development, Chapman and his team (Lotus) discovered that the pressure below the car could be greatly reduced if the front was close the track with the rear slightly higher (a 7-degree inclination seemed to work well).
Eventually, a lot of the development was banned on safety grounds, but not before teams had experimented with tunnels beneath the cars and sliding skirts at the side to control the air flow beneath the cars. Discoveries about the importance of air flow beneath the cars also brought out another critical aspect of race car design: ride height control.
Predictable Handling
For a driver, reliable predictable car handling is essential. He needs maximum levels of down-force as the brakes are applied, and he needs a stable predictable level during cornering and acceleration. If the height above ground of the car varies, the aero down-force will vary too. Keeping the chassis (also referred to as the platform) level at all times helps to ensure the stability a driver desires.
The behavior of a chassis in relation to its aerodynamics is directly related to the ride height. The height the chassis is set above ground (or the track) is accomplished by careful adjustment of the suspension. When changes of a little as 0.5 mm’s can make a big difference to an F1 car, it is clear that ride height adjustment is critical to a race car’s overall performance.
Measuring Points
From a measurement perspective, the ride heights are taken from the lowest point of a fixed part of the chassis. In the case of a single seater race car, this is often a rubbing strip (placed to stop the chassis being worn away on the track) placed under the chassis on the center line of the axles. On circle track cars, the selected measuring point is often below the main chassis tubes.
Before making any measurements, the race engineer must ensure the car is race ready. Race ready in this case is when the car has fuel, the driver is sitting in his normal driving position and the tire pressures are set at their hot pressures (if the tires have low pressures, the car will sit lower to the ground).
During testing, the engineer will monitor the ride heights, either in real time (telemetry) or by analyzing the recorded data after a track session. Although the driver will want a reasonably comfortable ride (soft springs etc.), the engineer will want a stable predictable platform. As with all race car settings, the engineer and driver will be forced to make compromises in the chassis/suspension set up to afford the best performance.
Effect of Tire Pressures
The ride height settings can be drastically effected by a number of parameters; in particular the tire pressures. During a race a driver may complain that the second set of tires didn’t perform as well as the first set, for instance. Although the tires were exactly the same (make, compound, size etc.) a slight variance in the pressures will make the car handle very differently; in fact, teams often adjust the tire pressures to compensate for a reported (by the driver) handling problem.
Although ride height settings will drastically affect the car’s performance, changing these heights will also affect other settings; in particular the corner weights. It is therefore imperative that the engineer takes into consideration the ‘knock-on’ effect of any changes (‘the car handles great, but we keep wearing a hole in the chassis’).
Making changes to the ride height of a race car will affect the performance: positively or negatively. By careful analysis by the engineer, and feedback from the driver, a car will perform at the top of its performance scale.
The author sets the front suspension on a F/BMW
|
Using a lazer light and height gauge
|
Ride height check on a Legends race car
|
Sparks fly on Rubens Barrichello's Brawn GP
|
What do you think about this article?
Latest Articles