Dynamic wheel load distribution
Under dynamic wheel load distribution is generally understood as the effect of the inertial force to the wheel load when changing the speed in the longitudinal direction of a wheeled vehicle. When braking, the wheel load is redistributed from the rear wheel to the front wheel; when accelerating, the opposite occurs.
Further dynamic wheel load distributions take place when cornering two-lane wheeled vehicles due to the change in speed in the direction of the transverse axis . Here the wheel load decreases on the inside of the curve and increases on the outside of the curve. The change in speed in the direction of the vertical axis , for example due to uneven road surfaces, also causes a dynamic change in the wheel load.
Static wheel load distributions result from air resistance , loading, trailer load or from inclines or slopes of the road.
As soon as a wheel is completely relieved, it lifts off the road if the wheel load is shifted further.
bicycle
When braking, the rear wheel is relieved, while the front wheel is loaded to the same extent. The flexibility of the suspension causes the vehicle to lower at the front. In extreme cases, braking on the front wheel leads to a stoppie , in which the two-wheeler only drives on the front wheel.
The opposite effect occurs when you accelerate strongly: the front wheel is relieved and the rear wheel is loaded, which in motorcycles with a small distance between the wheel axles and a high center of gravity can lead to wheelie , in which the motorcycle only rides on the rear wheel. In the worst case, both extremes end in the vehicle rolling over.
Multi-lane vehicles
In automobiles too, the front wheel loads increase when braking and rear when accelerating. Due to this fact, the drive wheels in a vehicle with front-wheel drive spin faster when accelerating than in a vehicle with rear-wheel drive, the drive wheels of which are pressed more strongly on the ground by the dynamic wheel load distribution.
In racing, braking is done in front of bends on the one hand to reduce speed, but on the other hand also to press the steering front wheels more on the asphalt and thus to achieve greater cornering force when turning into bends . The limits of this driving technique result from the loss of traction to be calculated with the help of Kamm's circle .
In commercial vehicles with drive formulas 6x4 and 6x6 can in the fully loaded state due to the relatively low axle portion of the front axle in pop-offs come to a momentary lifting of the front wheels. In automobiles, rollover due to dynamic wheel load distribution is only known from dragsters .
literature
- Hans-Hermann Braess, Ulrich Seiffert: Vieweg manual automotive technology. 2nd edition, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden, 2001, ISBN 3-528-13114-4