BCE0034: Expression in statements must only be executed for their side-effects

#pragma strict
var wheelFL : WheelCollider;
var wheelFR : WheelCollider;
var wheelRL : WheelCollider;
var wheelRR : WheelCollider;
var maxTorque : float = 50;
var Speed = 10;
function Start () {

}

function Update ()
{
wheelFR.motorTorque * Input.GetAxis ("Vertical") * Speed;
wheelFL.motorTorque * Input.GetAxis ("Vertical") * Speed;

}

And the problem is in * Speed

List 14 and 15 are just float expressions which aren’t used in any way. I guess the first “*” should be a “=” so you calculate Input.GetAxis ("Vertical") * Speed`` and assign it to wheelFR.motorTorque`

So the two lines

    wheelFR.motorTorque * Input.GetAxis ("Vertical") * Speed;
    wheelFL.motorTorque * Input.GetAxis ("Vertical") * Speed;

would become:

    wheelFR.motorTorque = Input.GetAxis ("Vertical") * Speed;
    wheelFL.motorTorque = Input.GetAxis ("Vertical") * Speed;
//                |     | |                                 |
//                |     | |                                 |
// variable_______/     | |                                 |
// assignment operator__/ \_________________________________/
// float expression________________________/

make speed a float. see if it works.