Steering Wheel Shimmy 55-75

First, look at the subject line closely. Most of the irrelevant quotes removed for clarity of point:

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Then Kevin replied:

OP stated:

So Kevin replied:

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Kev>>> > >> It is most certainly possible for any number of things to cause >>>>> the

D>>>>> > In theory extreme excessive positive caster can cause wheel shimmy.

So far I agree totally with this statement made by Don

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Then D>>>>Pretty sure he didn't mean caster, don't see how it's cause a shimmy, >>>

Kevin replied:

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 D> Ok let's get the facts straight ,

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).

Nuff said.

"A vehicle with too much (positive) caster will be hard to steer and> shimmy at low speeds.">

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.

Kevin

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 inerested.

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.

On Sun, 6 Aug 2006 02:12:44 -0500, "Kevin" wrote:

Don did not say the above.

> "A vehicle with too much (positive) caster will be hard to steer and>> shimmy at low speeds.">>

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 automotive field.

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 problem.

Sure...why not.

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.

Don

Forgiven. Were there any? :)