[VAL] Re: VAL Digest V1 #183 - Drum/hub balancing?

[waymark1@xxxxxxxx]

Balancing the hub/drum is not quite as important as balancing the
tire/wheel as it describes a much smaller radius (a 12" OD drum is a
pretty big one on travel trailers - many are 10") than the wheel and
tire, which is 26" diameter or larger. also the tire is much heavier than
the drum, and its weight is concentrated in its tread.
Nevertheless the hub/drum should be well balanced.
How does a drum get out of balance, anyway, if it was balanced accurately
when new? The only way I can think of is if a welded-on balance weight
came off the drum. Even if a drum is refinished ("turned"), only a few
hundredths of an inch of iron comes off, and it is evenly removed all the
way around. If a drum was so ovaled as to not be like this it should be
discarded. All of the travel and utility trailer drums I have seen are
too thin when new to stand much if any refinishing.

The hub/drum assembly should come already balanced from the mfr. of the
hub/drum. If it is out of balance it should be balanced before a
wheel/tire assembly is mounted. That way the wheels, once balanced, can
be interchanged or mounted without regard to position on the trailer or
the individual hub/drum.

Racing cars that go 220 mph do not have their tires/wheels balanced with
the hubs/brake rotors. The hubs/rotors are balanced by themselves, as are
the tire/wheel assemblies. Any tire/wheel can be mounted on any
appropriate hub without regard to positioning on the studs or splines
(knock-off type). Each part or permanent assembly is balanced by itself.
You won't see NASCAR, Indy or Formula pit crews installing wheels and
then balancing them before the car leaves the pit.
Al