First, look at the subject line closely.
Most of the irrelevant quotes removed for clarity of point:
Then Kevin replied:
So Kevin replied:
Kevin also said:
So far I agree totally with this statement made by Don
Then Don said:
I shoud have again added that the negative caster would only affect high
speed shimmy (as I have aleardy stated in earlier replies). Positive caster
is more prone to cause shimmy at lower speeds. Either way, incorect caster
can cause shimmy.
So Don Says:
Guess this just proves you can not believe everything you read on the
internet. Shopping carts do not have positive caster, they have negative
caster. Also, notice that it is only when you try to push one very fast
that the front wheels begin to shimmy (proving my point).
Yes, all these sites agree with me that incorrect caster can cause shimmy,
so I guess it must be a fact. I will admit that I wasn't specific about
positive caster being only at low speeds, but after all ,we were talking
about high speed shimmy, wich is what negative caster will cause.
Keep Smiling. I'm not trying to out wit you here Don. I can tell you are a
very inelligent and capable technician, but you have a tendance to critisize
any ideas that are different from your own. Just want you an the OP to
understand why I said what I said, and make my point clear to all who are
The point being. Although I do not necessarily think the OP has had a sudden
onset of Equal negtive caster on both sides it certainly is a possible cause
for his symptoms as he described them. After all, he claimed to have had
service to eliminate just about every other possible cause. Like I said,
somewhere along the line some of the service was not done correctly or it
would be fixed already. This is why I recomend starting back at the begining
and doing it in a logical order (tires/wheels/balance/runout first, then a
good alignment check (including all the normal inspections that go along
with a good alignment.
BTW, I spent too much time on this already, so forgive any typos. I'm not
even gunna run spell check.
Due to the nature of solving problems over the internet being mostly
Or its just something that has been repeated so many times it takes on
the aura of truth. There have always been lots of examples of this
and with the internet there even more!
Have you seen an example of this? Do you have a reference? I'm
willing to be educated about even the most obscure phenomena in the
Its hard for me to comment on it based on personal experience because
I have NEVER seen caster cause wheel shimmy period. My lifer
algnment guy at another shop says he HAS seen extreme positive caster
cause a type of shimmy or "nibble" at highway speed. He was referring
to deliberate extreme misadjustment in an attempt to cover up other
problems. Doing a google search I found page after page of references
to excess positive caster causing shimmy. About half the references
specified low speed, about half did not. In EVERY front end or
alignment texbook or articles I have read, in classes I have gone to,
I have only seen reference linking POSTIVE caster to shimmy. Googling
I did find two linking excess negative caster to shimmy one of which
pertained to model cars. The overwhelming mahjority linked only
postive caster to shimmy (and excess steering effort) and linked
negative caster only to "wander" -- which is, of course, absolutely
valid. I have personally experienced more than one vehicle with very
bad "wander" due to negative caster which is easily produced when
somebody goes "curb-surfing" and pushes the suspension back. This
"wander" was never accompanied by a shimmy that could not be fixed
with straight wheels and tires.
FWIW it is very hard to produce excessive positive caster on a car
through collision and REALLY hard to produce it at all on a vehicle
that does not have provision for caster adjustment.
Nor do I.
Possible...yes. In the sense that ANYTHING is possible. Hardly even
remotely likely IMHO.
And the tires are a very likely culprit. I am not a tire dealer so I
go to the tire franchise to buy tires just like John Q Public. I have
made more than one enemy there when I insist that they put the 3 out
of 4 egg-shaped specimens back on the shelf and sell them to some
other sucker. The usual answer is that it doesn't matter because they
will be "balanced."
Absolutely. Which I maintain has a 99% likelihood of fixing the
Inspections probably more relevant than the alignment itself. But
loose parts are usually a low speed issue. Except for the fact that
he said the problem persisted while coasting I could not entirely rule
out the inner CV joints.
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