At 11:37 22-02-1997 EST, you wrote:
>
>On Sat, 22 Feb 1997 10:05:50 EST larryhoy@juno.com (Larry A Hoy) writes:
>
>> I presently have steering wheel shake at
>>about 60 mph. I have eliminated wheel balance as a cause.
>
There are some possibilities:
1. Runout of a rim, especially after damage (e.g. hitting a curb).
Even when the wheels have been perfectly balanced,
a certain unroundness/eccentricity may also cause vibrations that cannot
be corrected by balancing.
2. Lack of uniformity in the tyre.
This means that the tyre is not equally stiff over its 360 degrees.
I used to work with a Germany-based company that makes tyre uniformity
measuring machines. Basically the principle is that a new tyre is clamped,
a small measuring wheel is pressed against the tyre with a certain
(spring) bias
and when the tyre under test is rotated slowly, the displacement is
determined.
A good tyre giving only minimal changes in displacement, a poor one
giving more.
Note that these machines are expensive and are only bought by the very best
tyre manufacturers.
Tyres are then sorted according to their uniformity. The best ones going to
car manufacturers, the somewhat lesser ones to better tyre outlets and
car dealerships, the last category going to cheap outlets and mail order
companies.
In all cases, these tyres are, of course, all of the same make and
exactly the same looking!
However, I might add that perhaps this situation is typical for the Germany
market as road speeds are much higher than elsewhere (Germany being probably
the only country in the world where there are no speed limits).
Higher speeds require narrower tolerances (unbalance, runout, etc) or,
put in another way, you run into problems earlier with higher speeds.
3. Did you check that you have the correct tyre size? Are the bearings,
king pin bushes etc. OK?
The shock absorbers?
4. Most important suggestion: DO NOT ELIMINATE WHEEL UNBALANCE AS A CAUSE
TOO EASILY!
I fully agree with Lawrie here.
Many mistakes have been made when balancing MG wheels!
Balancing spoke wheels isn't THAT easy because not everyone is aware that
you need
special adapters (this has been discussed before on this list).
However, I disagree with Lawrie in that balancing Rostyle wheels isn't
THAT easy either because often the central wheel hole is used for
centering on
a wheel balancer.
However, this is NOT suitable (intended for decorative hub cap only).
One shoud us the four wheel nut holes for centering, this is often not
done properly.
My serious recommendation: Try to borrow a set of wheels from another MG,
that is known NOT to have the vibration/shimmy problems you mention.
At least you can narrow down the possible cause.
I hope this is of some use to you.
Bert
<palte@rt.el.utwente.nl>
P.S. I did not get the original message yet.
P.S.2 The number of messages I get on this list gas grown to such an extent
that I cannot possiby read them all any more. In case there is some
duplication, I'm sorry. I can only select the messages I want to read
by the "Subject" line. I found that the Subject line does not always
exactly cover the subject any more......
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