Rigidbody.GetRelativePointVelocity

Description

The velocity relative to the rigidbody at the point relativePoint.

GetRelativePointVelocity will take the angularVelocity of the rigidbody into account when calculating the velocity.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    public Rigidbody rb;

    void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    // Get the velocity of a wheel, specified by its
    // position in local space.
    Vector3 CalcWheelVelocity(Vector3 localWheelPos)
    {
        return rb.GetPointVelocity(transform.TransformPoint(localWheelPos));
    }
}