Tech Articles

Initial Rotational Speed of Tires of a Dynamic Simulation in Adams Car

Tech Articles ID    KB8023272
Status:    Published
Published date:    11/28/2017
Updated:    06/14/2019
Reported In:   Adams - Adams Tire
  Adams - Adams Car
Created with Version:   Adams

Abstract (Question)

How the rotational speed of tires are calculated in Adams Car? What is the difference betweeen effective rolling radius and loaded radius?

Description (Answer)

Rotational speed of tires are not calculated with loaded radius. They are iterated by solver in static equilibrium process. For example, in a straight line event, you should be able to see multiple static simulations in the .msg file. Basically, Adams first settles down the vehicle on the road profile and find equilibrium. Tire rotational speed is not calculated yet during this phase. Then, Adams calls a VARSUB to calculates the 'virtual' tire rotational speed. Solver tries to get equilibrium, thus tries to reduce all accelerations to zero. That is used to get longitudinal forces on the tires as low as possible, and this happens at the correct rotational speed.


There are 2 types of tire radius,

  • Loaded radius, this is the distance in between the wheel center and the road. In general, Adams use tire vertical stiffness to calculate loaded radius.
  • Effective rolling radius, this is a 'virtual' radius, defined as Reff = vehicle speed/rotational speed.

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