Detention limit

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The grip limit is the colloquial term for the maximum transferable force between the tire and the road surface. The term is also used in racing and popular science literature. The power transmission up to the maximum of lateral force or circumferential force is assumed there as “quasi sticking”. The processes in the tire contact patch are more complicated, however, since sticking or sliding processes relate to individual tread particles and not to the tire as a whole. It would therefore be correct instead of adhesion limit the term traction limit to use. If the frictional connection limit is related to the normal force , a dimensionless coefficient is obtained which can be compared with the static friction coefficients of other friction pairings. Since the tire rubber belongs to the visco-elastic materials, the friction cannot be described in terms of Coulomb friction. So is z. For example, the “coefficient of static friction” determined in this way is not independent of the contact surface.

Circumferential force, lateral force

The forces that can be transmitted when driving straight ahead reach a maximum of between 8 and 30 percent slip, depending on the type of tire. Racing tires ( slicks ) can briefly achieve static friction coefficients of 5.0. When cornering, the direction of movement of the wheel contact point does not coincide with the wheel center plane, the power transmission then reaches its maximum between 4 and 10 degrees of slip angle . The profile particles located in the rear area of ​​the mountain pass slide.

If the amount of the acting forces (circumferential and lateral force) approaches the maximum transferable force idealistically defined in the Kamm circle , the tire begins to spin or slip away.

Influences on the detention limit

The grip limit is determined by the road / tire friction pairing . This is influenced by the roughness of the road (through different asphalt mixtures or other road surfaces such as blue basalt ), the mixture and the working temperature of the tires. Moisture, snow, ice , dust , sand , grit , leaves and other road contamination such as oil or gasoline residues from vehicles, soil or straw from agricultural equipment disrupt the interlocking of the tire surface with the ground and thus reduce the adhesion limit considerably.

The limit range of adhesion varies depending on the type of tire. This area tends to be larger in the case of treaded tires than in the case of slicks used in motorsport , in which the grip breaks off more quickly and which are therefore more difficult to control in the limit area. The use of the performance of such tires must therefore be learned and "experienced" anew on every route (due to changing road surfaces and weather conditions). Street-legal series tires, on the other hand, are easier to control, as the flexing of the tread blocks in the border area makes the loss of grip noticeable earlier.

Web links

Individual evidence

  1. ↑ Günter Leister: Vehicle tires and chassis development: strategy, methods, tools . Vieweg + Teubner, 2009, ISBN 978-3-8348-0671-0 , p. 109 ( limited preview in Google Book search).
  2. ↑ Stefan Breuer, Andrea Rohrbach-Kerl: Vehicle dynamics: Mechanics of the moving vehicle . Springer Vieweg, 2015, ISBN 978-3-658-09474-4 , pp. 12–25 ( limited preview in Google Book search).
  3. ↑ Michael Trzesniowski: race car technology , Vieweg and Teubner Verlag, Wiesbaden, 2nd edition 2010, ISBN 978-3-8348-0857-8
  4. ^ Karl-Heinz Dietsche, Robert Bosch GmbH: Kraftfahrtechnisches Taschenbuch. 27th edition, Friedr. Vieweg & Sohn Verlag, Wiesbaden, 2011, ISBN 978-3-8348-1440-1 , page 322
  5. ↑ Vittore Cossalter: Motorcycle Dynamics , 2nd edition 2006, ISBN 978-1430-30861-4