Relaxation length

Plot showing lateral force building up as a bicycle tire rolls forward at a 2.4º slip angle. The results from three separate test runs are superimposed.

Relaxation length is a property of pneumatic tires that describes the delay between when a slip angle is introduced and when the cornering force reaches its steady-state value.[1] It is also described as the distance that a tire rolls before the lateral force builds up to 63% of its steady-state value.[2] It can be calculated as the ratio of cornering stiffness over the lateral stiffness, where cornering stiffness is the ratio of cornering force over slip angle, and lateral stiffness is the ratio of lateral force over lateral displacement.[1]

  1. ^ a b Pacejka, Hans B. (2006). Tyre and vehicle dynamics (2nd ed.). SAE International. p. 22. ISBN 978-0-7680-1702-1. The relaxation length ... is an important parameter that controls the lag of the response of the side force to the input slip angle.
  2. ^ Cossalter, Vittore (2006). Motorcycle Dynamics (Second ed.). Lulu.com. p. 58. ISBN 978-1-4303-0861-4. The relaxation length represents the distance the wheel has to cover in order for the lateral force to reach 63% of the steady state force.