'On-Wheel' Tyre Balancing

Some tyre shops offer "on-wheel" tyre balancing services in addition to the usual wheel balancing. They do this on the wheel (while it is still attached to the car) by jacking up one side of the car, resulting in only one wheel spinning while the other is stationary. Would this cause any damage to the drive shaft, and other parts?

Reply:
Your fear are rightly founded. On car-balancing is normally done only on non-driven wheels, and should not be done on the drive wheels of a front-drive car. The reason is that when you spin only one wheel with the other still on the ground, the differential side gears are spinning at speeds they are never intended to under normal circumstances. This results in severe wearing of the side bearings.

In some cases, where it was really necessary, we lifted both wheels off the ground and spun them using engine power. But this is a procedure that can be quite dangerous because if the rear wheels are not chocked properly, the handbrake fails or the car fails off the stands, it can lunge forward and cause a lot of damage.

I would never recommend this procedure, because if the wheel balance cannot soed out with all the sophisticated electronic balancing equipment available today, there is really something wrong either with the wheel, tyre or even the hub assembly.