Coming from the NE Dirt Modified world, we are always looking to reduce the amount of friction that our tires need to withstand. This friction causes heat and wear in the tires. Our engines are longitudinally mounted, with the crankshaft lying parallel to the frame rails. The crankshaft rotates in a standard fashion, clockwise when viewed from the front. I have observed in the past that the setup changes needed from one car to another vary based upon what engine is in the car. A car with a high speed large cubic inch engine requires a more aggressive suspension change than one with a low speed, smaller engine. My background in Mechanical engineering leads me to think that the larger moment of inertia in the larger engine, coupled with the higher engine speed and therefore higher angular frequency, means that the engine of the car has higher angular momentum. Could this cause the engine to induce a force on the car which counteracts or couples with the force of friction from the tires?


When you say “higher moment of inertia” or “higher angular momentum” I assume you are referring to a rotating rigid object correct? This might be the fly wheel or torque converter (correct me as to what since my knowledge about cars is minimal). It seems to me that you should be using the idea of torque then asking how varying this will vary other things.

Torque is the product of the moment of inertia and angular acceleration (of the rotating object being referred to). And angular acceleration is a change in angular velocity and if angular velocity increases, angular momentum increases.

Having said that, because the friction on a tire is the force that resists its rotation when driving, this frictional force is equal to the normal force on the tire (that is, the weight of the tire and the weight of the engine and everything else that pushes down on the tire) multiplied by the coefficient of (Kinetic) friction. This coefficient depends mainly on the nature of the tire/ground surfaces. And the other factors you mentioned do not. However if things like torque, angular momentum and moment of inertia cause an additional downward force on the tires, then yes, the friction force will increase.

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    $\begingroup$ Not sure what the OP was getting at, but there's also the sort-of-gyroscopic effect when the car enters a curve and the rotating parts of the drive train resist this delta (vector) angular momentum $\endgroup$ Oct 14 '20 at 12:29
  • $\begingroup$ This gyroscopic effect is what im getting at, whether the rotation of the crankshaft and subsequent driveline components causes a force to be imparted about the vertical axis of the car. I believe with the rotation of the crankshaft, as well as the desired rotation of the car turning left, that the gyroscopic effect resists the force of friction. $\endgroup$
    – Rylee Gill
    Oct 14 '20 at 18:00

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