Electric brake drums - how to correct out of balance

Quote:
The drums are NOT balanced from the factory and there is little point in balancing wheels under this condition.
--------------------------------------------------------------------------
I have seen many drums w/ balance weights spot welded (fused) to the drums, and others that have been drilled.
And if the wheels are spun balanced on the vehicle (like they used to be) or the drum and wheel are balanced as an assembly off the vehicle, the entire assembly gets balanced. So there is a way around out of balance drums.

Most likely the drum was not machined correct during manufacture. I would bet you will find it is not concentric. Having the drum returned so it is concentric may help.

But it is most likely junk.

Balance beads in tires that have been balanced may offset minor drum balance.

Trailer drums are not balanced like automotive were. If you look you will not find balance weights or machine cuts like you will find on an automotive drum.

Balancing a drum is not for the faint of heart. it is a professional job.

IF in fact the drum is out of balance some shops may have the ability to do it, it is done by welding metal to the drum in an area where it won't be bothered.

Another posibility is the drum may need to be turned or it may be out of round.

Again a professional who has the tools (And sadly those are rare these days) is needed to figure it out... I can not, and do not know off hand anyone who can, but your Tire Professional MIGHT. I stress MIGHT. I know one weld shop that might too but less you are in metro Detroit,, Not much joy there. (Marty's On Telegraph between 5 and 6 mile I as I recall)

I am sure there is a mathimatical equasion to determine the effect of a rotating mass 6 inches from the center versus 15 inches from the center. If the drum was manufactured by a reputable company the ammount of out of balance should be so small as to be barely noitcable. Now a tire out of balance that can be felt, or rather seen as most people do not ride in a trailer to feel the out of balance. Balancing trailer tires should be sufficient for most folks.

I've been harping on this subject for a long time. The drums are NOT balanced from the factory and there is little point in balancing wheels under this condition. Buying new drums is a crapshoot because they may be even worse than the ones you are replacing. The OP is the first person that has come on here having actually tested the balance of the drums.

OP, you are correct that there is no provision for balancing. What I do is clean out ALL the grease from the bearings, add a few drops of light oil, and find the heavy spot. Then mount the tire/wheel with the heavy spot opposite the drum heavy spot. Mark everything and add balance weights to the wheel till it comes into balance. Clean the bearings, pack grease and reassemble with a new grease seal. Using this procedure, you should be able to get the entire assemblies within 1/2 oz. If you just balance the tire, you could be out 6 oz. or more.

If you sure its the drum out of balance so bad that it rotates against the resistence of the bearings, grease, etc, its junk, right from the get go !

Buy a new one, and find out what's wrong with the rest of it, bearings seal and brakes should not let the drum turn by itself if off the ground with no wheel.

They come already balanced. Your method of checking for balance is not a good way to judge it. There is a lot more affecting it when installed. The brakes could be dragging, the magnet is dragging, the bearings, the wheel seal, the brake dust in the drum, drum warped from heat, grease packed in the hub, etc..

Moved from Forum Technical Support