When is it necessary ?

If you have had your wheels balanced off your car, and still have a vibration, you may need on car balancing. It is important to make sure it is not some other mechanical failure first. Universal joints, constant velocity joints, engine miss can also cause vibration, these must be checked before an on car balance is performed.

Why is it necessary ?

In a perfect world it would not be needed. Every rotating component on your vehicle is supposed to be balanced separately, but if a weight comes off brake drum or out of a brake rotor, your vehicle can develop a vibration only on car balancing can repair.

AT CAN-ALIGNMENT I USE A VIBRATION SENSOR UNDER THE AXLE OR CONTROL ARM, THUS ALLOWING THE WHEELS TO BE SPUN UP THE WAY YOUR AUTO GOES DOWN THE ROAD, INCLUDING HUB CAPS.