Re: [VAL] balancing of tires, wheels hubs and drums

["Oliver Filippi" <ofilippi@xxxxxxxxxxxx>]

The right way to do this would be to balance the tire/wheel assembly, and
the hub/drum SEPARATELY. [ Ideally, one should balance the hub and drum
separately as well.]  Thus the trailer's tires can be rotated without
affecting the balance.

Some time ago, I called a number of machine shops that balance racing
engines.  These are the only firms that I have found that are equipped (or
know how to balance a hub/and or drum).  I am sure there are other sources,
but I did not persue the issue any further.

Spin balancing the tire on the trailer will balance the wheel AND the
hub/drum as a single unit.  However, besides the drawback of not being able
to rotate the tires, one has to be careful to remount the wheel in exactly
the same position on the hub if it is removed to, say check the condition of
the brake shoes or magnets (same studs to drum and wheel bolt holes).  There
is also another subtle but significant problem with this approach:  The
wheel/tire assembly will not be dynamically balanced - which is achieved on
the good off the vehicle computer balancers (Hoffman, Coates, FMC, etc.).
[The dynamic balance is the lateral balance between the inside and outside
of the tire/wheel assembly (eliminating any side to side wobble).]

I do not know the answer to the following questions, which are relavent to
this discussion:  Namely, how much of an effect can an out of balance hub
and brake drum contribute?  This has two components. 1) How much rotational
imbalance (variation) is there in a typical hub and drum; and 2) how
significant is this imbalance in the scheme of things?

Since the hub is a relatively small diameter compared to the wheel, it is
not going to contribute as much imbalance as the larger diameter tire
assembly.  The drum could have a larger impact, but only if the imbalance is
significant. Thus we may be getting overly concerned about a trivial
component in the equation.

My guess is that the hub and brake drum are not a major variable. Hence go
with the off the vehicle computerized spin balance.

For what it's worth, the German Hoffman is probably the best balancer (they
are now imported by FMC).  Hoffman invented the computer gyro technology,
and their machines are used in many industries to balance cutterheads and
other rotating assemblies where vibration is an undesireable factor.

Oliver Filippi