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Calculation of friction coefficient between wheel and road

  1. Nov 25, 2014 #1


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    Hi all,

    I need to calculate the friction coefficient between road and the tyre of the car.
    I came across few answers like which solves as from the following torque equation.

    Engine torque = braking torque + acceleration troque + Inertial torque + drag torque + rolling resistance.

    For braking, Engine torque = 0. and the braking torque is assumed to be Cp * (Braking pressure).Acceleration torque is taken as (F = (Mue)* (Normal force i.e., the weight on the wheel)).

    The inertial component is taken as J*(omega_dot). where omega_dot is the derivative of angular velocity of the wheel.

    is the inertial torque component significant? can it be neglected?

    How can the Mue of the road at slip = 0 be calculated as the Mue varies with the slip?
  2. jcsd
  3. Nov 25, 2014 #2


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    Gold Member

    You can neglect the inertial term provided you use massless wheels for which J = 0; otherwise, no, it must be included.

    You are asking too much of a simple model here. The Coulomb friction model, Ffriction <= mu * Fnormal, does not depend on slip. When you use the equals sign, you are saying that slip is (1) impending or (2) slip is occurring.
  4. Nov 25, 2014 #3


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    Thanks for the reply, I would like to know in the case where vehicle is already in slip. I read some where that the friction between the tire and road vary with the variation in slip. So, I am trying to calculate the variation of Mue(Braking force coefficient) with respect to slip. Please refer the following attachment to know about its variation.
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