On-Car Wheel balancing

[Dangermouse]

I have read a few times on here that several people recommend balancing the wheels on the car. I'll be honest and say that I have never seen this done, and I don't think the usual chain wheel shops do it. So I am looking for a little education.

I understand the benefit (balancing the whole drive train) but wonder why it isn't commonly done on modern cars.

For those that have done it, what components are commonly out of balance apart from the wheel itself?

Are there any tire shop chains that can do it? Or is it more of a mom-and-pop sort of throwback thing.

(Any local recommendations in Atlanta)

[DMCMW Dave]

In theory, you shouldn't need that as the other rotating mass, the brake rotor, is already balanced. The brake rotor mass is also much more centered so it is not a critical to balance as the outer structure of the tire.

If you do happen to have an out of balance rotor, this will cover for it, BUT you must then forever put the same tires on the same rotore oriented on the same lug studs.

I would not bother.

[David T]

You should not do "On Car" balancing. It is not necessary for cars and if it is you should replace the out-of-balance parts, not try to balance them. The balancing is only meant to balance the rotating mass of the wheel, tire, rotor and hub assembly, not half-shafts, or any other parts in the drivetrain. Each part is supposed to be balanced separately except for the rim and the tire. They are balanced as an assembly. Most shops charge a lot more to balance that way as opposed to off the car. There is also a certain amount of danger if it is not done properly and safely. Bottom line-find a shop that can do the balancing of each wheel and tire assembly off the car. If you still have vibration find and fix the problem. It should not take balancing to do it. The other area where you do balancing is parts inside the motor. Normally you only have to do it when you reassemble a motor.
David Teitelbaum

[LEVY]

I have read a few times on here that several people recommend balancing the wheels on the car. I'll be honest and say that I have never seen this done, and I don't think the usual chain wheel shops do it. So I am looking for a little education.

I understand the benefit (balancing the whole drive train) but wonder why it isn't commonly done on modern cars.

For those that have done it, what components are commonly out of balance apart from the wheel itself?

Are there any tire shop chains that can do it? Or is it more of a mom-and-pop sort of throwback thing.

(Any local recommendations in Atlanta)


On the car balancing is nothing new, been done for decades. As Dave and David stated, not needed and it may only help you mask a dangerous problem that need to be corrected.

I don't believe any tire shop chain would do it, for liability purposes.


David, how do you balance the motor?

I'm from the old school and it would take me a lot of time to do it but at the end the engine would feel like an electric motor.

Is there any easier way to balance the motor now days?


LEVY



You should not do "On Car" balancing. It is not necessary for cars and if it is you should replace the out-of-balance parts, not try to balance them. The balancing is only meant to balance the rotating mass of the wheel, tire, rotor and hub assembly, not half-shafts, or any other parts in the drivetrain. Each part is supposed to be balanced separately except for the rim and the tire. They are balanced as an assembly. Most shops charge a lot more to balance that way as opposed to off the car. There is also a certain amount of danger if it is not done properly and safely. Bottom line-find a shop that can do the balancing of each wheel and tire assembly off the car. If you still have vibration find and fix the problem. It should not take balancing to do it. The other area where you do balancing is parts inside the motor. Normally you only have to do it when you reassemble a motor.
David Teitelbaum

[Dangermouse]

fwiw, I don't need this done on my car.

An owner on another forum was having wheel balance problems. He had his wheels balanced, off car, put them back on and had a much more pronounce out-of-balance than before. Which made me think of what some people had said on here about on-car balancing. Perhaps his had been balance on-car before and he had messed it up now by taking the wheels off.

I had never dealt with on-car balancing, so I thought I'd investigate it some more.

[David T]

To balance the motor you first weigh each piston, connecting rod, caps, bolts, rings, bearings, etc. You match up the parts so they all weigh the same or you remove materiel so they all weigh the same. Then you put the crankshaft into a special balancing machine with bobweights to simulate the piston-connecting rod assembly. Usually you also attach the flywheel. You run the machine and add or remove weight from the crankshaft and/or the flywheel. This is specialty machine shop work which you would send the parts out for. An internal combustion engine will never run as smooth as an electric motor, it fires in pulses which are absorbed by the crankshaft and the flywheel. Many manufacturers do not balance their motors. The production process is good enough that all of the parts are close enough in tolerance so the motor, when assembled, is balanced "good enough". When a builder hand assembles a motor he will usually "blueprint" it (make sure each and every part is as exact as it can be) and try to make the motor to better tolerances than a mass production assembly system allows. This can include port matching and polishing, flashing removal, shot peening the high stress parts, hand fitting each part to it's mate, etc. There is a whole science (and art) to "blueprinting" a motor. Balancing is only a part of it.
David Teitelbaum

[LEVY]

To balance the motor you first weigh each piston, connecting rod, caps, bolts, rings, bearings, etc. You match up the parts so they all weigh the same or you remove materiel so they all weigh the same. Then you put the crankshaft into a special balancing machine with bobweights to simulate the piston-connecting rod assembly. Usually you also attach the flywheel. You run the machine and add or remove weight from the crankshaft and/or the flywheel. This is specialty machine shop work which you would send the parts out for. An internal combustion engine will never run as smooth as an electric motor, it fires in pulses which are absorbed by the crankshaft and the flywheel. Many manufacturers do not balance their motors. The production process is good enough that all of the parts are close enough in tolerance so the motor, when assembled, is balanced "good enough". When a builder hand assembles a motor he will usually "blueprint" it (make sure each and every part is as exact as it can be) and try to make the motor to better tolerances than a mass production assembly system allows. This can include port matching and polishing, flashing removal, shot peening the high stress parts, hand fitting each part to it's mate, etc. There is a whole science (and art) to "blueprinting" a motor. Balancing is only a part of it.
David Teitelbaum


Thank you for your response, I know how to balance a motor, just wanted to know if there is something new. I would do more than just weight pistons and connecting rods.

I know it will never run as an electric motor but seems like you have never operated a well balanced motor.


LEVY

[David T]

Some ICE (Internal Combustion Engines) run VERY smooth. It is how it is designed and built. A lot has to do with firing order, internal dampening, # of bearing journals, angle between the banks, # of cylinders, mass production practices, etc. It starts with all of the engineering and economic compromises to make a car and be able to sell it at particular price. The PRV is not all that smooth and with the K-Jet it also hunts at idle. Not the smoothest engine and the gearing for the 5-speed is not optimized to the car's weight. For it's price it is acceptable, no worse than any other car in it's class at the time.
David Teitelbaum