Neil et all,
I have a static bubble balance machine and balance all my 19" TC/MMM and 15"
MGA/Elva wheels on it. Never a problem. I agree with Neil, the wheel should
be statically balanced when the job is done. On a TC/MMM wheel, your options
are to use lead wrap around the spokes ( not very elegant ) or stick-on mag
wheel weights on the rim adjacent to the spokes. Either method gets the
weights very close to the spoke center line of the wheel. Therefore the
effect of the weights is minimal on the dynamic balance. I put the stick-on
weight on the inside of the spokes if only a small weight, or split
inside/outside if a large weight is required. This to try to avoid dynamic
unbalance caused by a large weight.
I am also a dealer for MWS wire wheels and I have had many experiences with
"knowledgeable" technicians balancing wire wheels. They often get it wrong
because they do not hold the wheel properly on the balance machine. You must
hold the wheel as it is mounted on the car. That is the inner cone of the
wheel hub rests on a back cone on the machine and the outer end of the wheel
hub must be held by a special adapter that grips the OUTSIDE of the wheel
where the knock-off is mounted. Often the technician simply puts a tapered
cone on the outside bore of the wheel and so centers on the inner diameter
of the wheel and that may not be a true machined surface. Result, bad wobble
which is sometimes seen as a bent wheel.
Regards, Bob Grunau
I wouldn't claim to be the most expert here on the subject, but if it isn't
statically balanced then it isn't balanced. It may show up as having no
unbalance on the machine, but that does not necessarily mean it's right!
My guess is that the wheel should be statically balanced (resulting in one
balance weight) before being run up on the machine when the remaining
'dynamic unbalance' is corrected by adding two more weights as described (ie
diametrically opposite each other one on the inner rim and the other on the
outer rim).
> Gentlemen
>
> I'm sure that in this august group there is someone with theoretical and
> practical knowledge of wheel balancing.
>
> I think I understand the difference between static and dynamic balance. A
> freely pivoted wheel which is in static balance will remain in any
position to
> which it is rotated. However, the weight may not all be in the same plane:
> that is a heavy point on the out-facing rim of the wheel may be
> counterbalanced by a heavy spot diametrically opposite, but on the
in-facing
> rim of the wheel.
>
> If this is the case, when the wheel spins the heavy points will act
together
> to twist the wheel at right angles to its axis of rotation, and it will
> wobble. It is not in #dynamic# balance, and will require appropriate
balance
> weights added to the in- and out-facing rims to achieve this and stop the
> wobble.
>
> As I understand it, the difference between static and dynamic balance is
small
> for large diameter, narrow wheels/tyres (MMM and TABC) and absolutely
crucial
> for small diameter, wide tyres (most more modern cars).
>
> I've just watched a friend balancing the 19" wheels for our J2. He was
using
> an old (but I believe reliable) wheel balancing machine: it has a setup
rather
> like a front stub, so that an unbalanced wheel causes a considerable
wobble in
> the shaft. A mechanical indicator guides the operator on where balance
weight
> is required.
>
> Each wheel had weights progressively fitted until it spun true on the
machine,
> but in most cases the wheel in not in #static# balance at the end, and I
don't
> see how this can be.
>
> Would our experts please enlighten me?
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