Ride Height
Definition
Ride height is the clearance between the bottom of the car and the road surface. It has a significant impact on the car’s centre of gravity, and thus on its behaviour when cornering or braking – essentially any situation involving a shift in weight. Because a great amount of aerodynamic downforce is created by the F1 underbody, ride height is also crucial for overall grip generated by the aerodynamic package. The underbody aerodynamics are very sensitive to ride height.
Benefits of Lower Ride Height
There are compelling reasons for reducing ride height. In general, lowering the ride height brings the centre of gravity of the car closer to the ground, making the car more responsive by decreasing body roll, since the car’s mass is now positioned lower. Additionally, the downforce created by a low F1 car is greater.
Raising the ride height has the opposite effect, increasing body roll.
Trade-offs and Considerations
As with all adjustable parts of an F1 car that can be tuned, both over-tuning and under-tuning have their drawbacks. A lower ride height at the front than at the rear will induce weight transfer to the front, increasing the load on the front axle. This may be the desired outcome for certain circuits or conditions.
Ride height also affects the available suspension travel rate, so engineers must ensure the spring rate is high enough to prevent the suspension from “bottoming out”. If the ride height is set too low, the suspension will not function effectively. The trickiest challenge is setting the ride height as low as possible for maximum tire grip, downforce, and overall neutral handling balance, while still allowing sufficient suspension travel.
During a wet race, ride height should be raised to allow water pushed beneath the car by air entering below the underbody to flow freely beneath the “wooden” plank". Otherwise, the underbody can effectively surf on a layer of water, resulting in an undriveable car – a phenomenon known as body aquaplaning.
Rake Angle
The deviation of the floor plane from horizontal is called the rake angle. A positive rake angle means the rear end is higher, while a negative rake angle means the front is higher. Negative rake is not used in racing.
Lower front / higher rear ride height: The weight of the car shifts towards the front, providing more stability while accelerating. Brake response is faster since weight is already concentrated where braking power is greatest. There is also a significant aerodynamic advantage, as the entire underbody of the car acts somewhat like a large diffuser.
Equal front and rear ride height: Weight is distributed equally between both axles.
Higher front / lower rear ride height: The weight of the car shifts to the rear, providing immediate throttle response during acceleration. This is not a bad configuration for the start phase, but braking response suffers significantly. Since Formula 1 is not a drag race, this configuration is rarely used. Additionally, in a Formula 1 car, this setup increases aerodynamic uplift.
Bumpy Circuits
On very bumpy circuits such as Monaco, teams increase the ride height and adjust spring rates and dampers accordingly. This “soaks up” the bumps more effectively.
FIA Restrictions on Steering-Linked Ride Height Changes
Teams continually seek to reduce the height of the front of the car, if not the entire car. In December 2017, the FIA clamped down on teams using steering angle to gain an aerodynamic advantage through clever front suspension geometry systems. Charlie Whiting issued a Technical Directive to the teams, making it clear that the governing body believed some teams in 2017 had designed their suspension and steering systems to lower the front ride height during cornering, potentially providing an aerodynamic benefit and hence increasing grip. While some change in ride height is inevitable when the steering wheel is moved from lock to lock, the FIA suspected that the effect of certain systems went far beyond an incidental change, and any non-incidental change of ride height would affect the aerodynamic performance of the car.
Teams were asked to provide all relevant documentation showing what effect steering had on the front ride height of the car, that this effect was incidental, and that ride height should change by no more than 5.0 mm when the steering wheel was moved from lock to lock.
Whiting referenced a 24-year-old FIA International Court of Appeal ruling on suspension as a precedent for the interpretation of the key F1 technical regulation concerning aerodynamic influence. One section of the regulations reads: “any car system, device or procedure which uses driver movement as a means of altering the aerodynamic characteristics of the car is prohibited.” This may be the wording the FIA used to justify its stance. Hence, any change of front ride height when the steering wheel is moved from lock to lock should be wholly incidental.
For further analysis, ex-Formula 1 technical director Gary Anderson offered his view at motorsport.com on the FIA’s newest technical directive aimed at limiting aerodynamic advantage gained through front suspension systems.