Road-holding

Road-holding – also written as roadholding and road holding – (in French being called "tenue de route", in German "Beibehaltung der Spur"), is essentially determined by the ability of a vehicle to stay on the road and on a desired trajectory of motion, whatever the circumstances (in curves, on greasy, wet or low-grip ground, loaded or not, etc.) may be, but also by the degree of ease that a driver may sense in controlling it in an emergency situation.^[1] (Hereby, the laws of nature as a framework, including the gravitational field of the planet Earth as well as the phenomenon of inertia, are tacitly assumed as given.)

In the above context, the straight-line stability of a vehicle – which is concomitant with its ability to stay on a desired trajectory of motion – necessitates a certain degree of understeering.^[2]

The capability to smooth down the road imperfections, affects both the comfort and the road-holding of a vehicle. To improve comfort in this regard means, basically, to limit the vertical acceleration fluctuations of the vehicle body and hence of passengers. To improve road-holding means, among other things, to limit the fluctuations of the vertical force that each tire exchanges with the road. Therefore, modeling and simulation using realistic suspension-damping models, taking the vehicle tires into account, offer a straightforward opportunity for road-holding improvement of vehicles.^[3] Optimization techniques for this purpose are also known.^[4] The application of inerters is a very new possibility in this regard, although this technology is more destined to race cars than to ordinary vehicle applications.^[5]

As a more sophisticated means for improving road-holding, active suspension – involving sensors, actuators and microcontrollers – may also serve.^[6]

For vehicle speeds above approximately 40 meters per second, the effects of aerodynamic forces at an automobile (that is not designed in a too odd manner) tend to become sensible for its road-holding.^[7]

Beyond what has been previously mentioned, electronic stability control, if being present on a vehicle and properly tuned, will have a stabilizing influence on the trajectory of motion and accordingly an improving effect on road-holding of that vehicle.

See also

• Automobile handling
• Cornering force
• Directional stability
• Grip (auto racing)
• Traction (engineering)

References

1. Campbell, C.: Automobile suspensions. Chapman&Hall, London 1981, pp. 105 f.
2. Campbell, C.: Automobile suspensions. Chapman&Hall, London 1981, p. 106.
3. Guiggiani, M.: The science of vehicle dynamics: handling, braking, and ride of road and race cars. 2nd edition. Springer, Cham [2018], ISBN 978-3-319-73219-0, pp. 417-460.
4. Shirahatti, A., Prasad, P. S. S.: Optimal design of passenger car suspension for ride and road holding. In: Journal of the Brazilian Society of Mechanical Sciences and Engineering. Vol. 30, Fasc. 1, pp. 66-76, 2008.
5. Guiggiani, M.: The science of vehicle dynamics: handling, braking, and ride of road and race cars. 2nd edition. Springer, Cham [2018], ISBN 978-3-319-73219-0, p. 426.
6. Bharali, J., Garg, N.: Efficient ride quality and road holding improvement for active suspension system. In: 14th IEEE India Council International Conference (INDICON), December 15–17, 2017, Roorkee, India. IEEE 2018, pp. 1179-1184.
7. Doniselli, C. et al.: Aerodynamic effects on ride comfort and road holding of automobiles. In: International Journal of Vehicle Mechanics and Mobility. Vol. 25, Issue Suppl. 1, pp. 99-125, 1996.