[VAL] Re: VAL Digest V1 #172 - Trailer wheel balancing?

[waymark1@xxxxxxxx]

"how important is hub and drum balancing?"
All wheels on any highway vehicle (anything that will be run over 25 or
30 mph) should be balanced.
Trailer wheels, being on a rigid axle (they won't turn from side to
side), cannot wobble side-to-side, so static balancing is OK.
Out of balance wheels will "hop," which wears the suspension and shocks,
shakes the trailer and wears the tires unevenly. Severe hop will
cyclically reduce the adhesion of the tire to the road. It can even lift
the tire off the road if it is bad enough; however if it was that bad I'd
suspect either a defective tire or a big hunk of mud stuck to the inside
of the wheel rim.
Dynamic (spin) balancing is necessary only on swiveling steering wheels.
It is just fine on all wheels - it's how racing and aircraft wheels/tires
are balanced.

"short of sending my hubs, tires and wheels to california, where would a
guy get this done?"
Any tire shop or wheel and alignment shop should be able to balance
trailer wheels. There is nothing distinctive about trailer wheels. They
are like light truck wheels of similar design. If you don't want to take
your trailer to the shop, just take the wheels off the hubs with the
trailer on solid, stable jack stands of suitable capacity and height and
take them to the shop. As Dr. J mentions, heavy truck tires are balanced
on the truck like service stations did with car wheels 30+ years ago.

As the hub and drum are cast in one piece (on most trailer axles) it will
be balanced in unit. It should have come balanced from the manufacturer
when new. If the drum has been turned (refinished inside) it should
remain in balance as the small amount of iron that is cut off will be
even all the way around. I cannot imagine that a drum would be enough out
of balance to be worth bothering with unless a welded-on balance weight
(used on many kinds of drums) has come off. If the drum is very much out
of balance it will be evident if the wheel is removed. Make sure the
brake shoes are not dragging. The bearings should have a trace of play in
them. If the drum is spun with the hand, see if it stops in the same
place every time. If it does, or worse turns on its own to one angle and
then goes back and forth like a pendulum there is a real problem with the
drum. I've never seen a vehicle drum or disc that did that way (like a
bicycle wheel that is held off the ground - they are almost always out of
balance and are very free turning; see Joy's description of balancing a
motorcycle wheel, below).
The wheel and tire may be balanced off the hub on a static (bubble)
balancer or on a dynamic (spin) balancer. The wheel should be balanced
already when it came from the wheel manufacturer when new. Anything that
would cause the wheel itself to go out of balance would ruin the wheel.
Just make sure it is clean of all dirt, tar, stuck-on rocks, etc., which
is common on the back side of the wheel.

High quality tires generally require less weights to balance. I used to
run Michelin XAs tires and they were within 1/4 ounce of true (the tire
needed only 1/4 oz. to balance it to "0" on the balancing machine, which
machine's book said was good to 120 mph. Later I put a set of lower
quality American brand tires on and two of them required 4 ounces of
weights each. That means the casing/tread had quite thick and thin spots.
They also were eccentric, which cannot be cured with balancing. Bleah!
Al