65mph shimmy

[ptrfair]

So this weekend i took Bonne out on a road trip down 95 from Philadelphia to Baltimore. Occasionally i noticed a vibration in the wheels but only every so often and for a few minutes at a shot. I also make this trip every so often and notice that this happens in the same areas all the time....maybe its I95??

With all the $$ ive invested in the front end i doubt its my brand new axles...both of them=) lol and the engine mounts are fixed.....so i say .. umm whats up? I guess the question is, those of you who have the shimmy at 65mph, when does it go away and when does it start? Im wondering if its just the highway. I notice at 80 the probelem goes away and i JUST had the tires balanced.

If a tire is balanced with 30 PSI in the wheels, then the pressure drops over time, would that cause the tire to wear out of balance or is it just a crazy thought?? I can live with this problem, just like to know whats up

[golfyeti]

This shimmy is a pet peave of mine so I'll always chime in on the subject.

Here are some observations:

- At 65 MPH I place the car in Neutral -- shimmy remains until the car coasts to outside of the "Shimmy Zone" which is approx 62 MPH to 70 MPH on my car. This gives me a clue that it is not the (engaged) drivetrain causing the shimmy.

- The shimmey gradually increases as you rise to from 62 to 66 MPH where it is at about it's worst and then decreases equally to hardly noticeable at 72+ MPH

- It does not come back at even much higher speeds

- on rare occassions I will get a similar shimmy at right about 50 MPH, but only rarely

- I have balanced and rotated my tires many times with very little effect (although it appeared to have a little bit of an effect once)

- I have replaced my front rotors a week ago - not the slightest difference.

- I have replaced my end-link bushings all around - tighter corering - but still shimmies.

- I have very bad rear shocks mounts (somehow connected...who knows)

Here's one of my most interesting obeservations:

The "Shimmy Zone" will drift higher or lower depending on wind direction so this is why I suspected that their is an aerodynamic issue related to this. The Shimmy Zone will occur only at higher speeds with the wind in your back and at lower speeds with the wind in your face.
This had led me to believe for a while that the front wind dam (I think that's what they call the lip under the bumber) was the culprit because it appears somewhat loose, and the theory goes like this...at low speeds a loose (or poorly designed) dam would not cause any turbulence or oscillation in the aire flowing around and under it. As you move faster the oscilation frequency or strenth would start to affect the overall car. As you move yet faster to past 70 MPH, the wind dam gets pressed back hard enough to be solidly planted against something where the dam no longer oscilates because of the higher/constant wind pressure securing it in place.

Lastly, the techincian who replaced my rotors mention that a front tie-rod was a little loose. I haven't replaced it yet but as for the shimmy I'm not sure if hte tie-rod is "cause or effect"...

That's it for now...I was really hoping that the CV Joints were the solution but apparently not.

My next test will be to install comepletely different tires and wheels. I will report on any new observations.

[gmman]

i have had similar problems over the years. it has always turned out to be tire balance. i don't know if it is the people operating the balance machines or the sensitivity to out-of-balance conditions by the machines. i do know that i have to start with a good quality tire and for me it has been michelin, but even then it will depend on the balance machine or the person operating the balance machine. on some occasions i have asked that a set of tires be replaced under warranty because of vibration and then the company would get serious about whether they were properly balanced or not and guess what, after rebalancing there was no vibration at any speed.

the problem is so serious that i will not rotate my tires. when a tire is worn to the point of being replaced i will replace one at the time to be able to determine when a vibration occurs and can keep the problem isolated to only one wheel. i have even thought that someone should design a piece of equipment that could be strapped onto the car and detect which wheel or wheels was generating vibration. obviously there aren't enough of us that complain about this problem to make such an invention profitable. maybe i am just to sensitive about this kind of vibration (my wife thinks i am peculiar in other ways too).

seems like i have read or heard that certain GM models were prone to such vibration but i can't remember where. i own a ford product that never seems to exhibit this tendency but it came with michelins from the factory.

i have also changed rotors out of desperation with no success.

[Skippy1827]

Research "Road Force" Balancing of your tires

[golfyeti]

Research "Road Force" Balancing of your tires

Yes, the Hunter 5000 or something like that. Haven't found a shop that uses it. Besides, it's too common of a 2000+Bonne problem on too many different types of tires and no matter the post-rotation position of each tire, to be a single tire balance issue. And to me this is the evidence:

- It (the car shimmy) does not come back at even much higher speeds (and I mean MUCH higher speeds...right up to the limiter...)

I beleive that an out of balance tire would only cause bigger and bigger issues the higher the speed you go.

[bonnevillain]

I agree. I doubt it is tires, since I have vibration from 65 to 75 or so, nothing from 80 up to 125 though. I do plan to get my tires road force balanced next time though, and am replacing my endlinks and struts. We'll see if that helps.

I have a hard time thinking the plastic wind dam could cause that... maybe you could have someone in another car watch it for movement, but i doubt that would be it.

[CorbinDallas]

It's not just balance but can be out of round
any OOR tire can balance out to zero and most newer balancers and shops only spin at slower speeds
Jack your car in the air enough to put a socket undet the tire and spin by hand and look for any OOR, most MFG's give a spec, but you would want NO more than 1/16th

A OOR tire can give the feel at a certain speed that goes away, because as the tire rotates faster, it becomes more symetrical in circumferance but still in balance
Tires can have hard spots in the rubber as well, which is why RoadForce is benificial

The only true way to eminate it being T/W is to have them "Shaved" or "Trued"
[former goodyear tech and use to cut tires for SCCA]

[swampthing]

http://www.pontiacbonnevilleclub.com/fo ... road+force

road force didn't help me but that could have been the mechanics error as well

[ptrfair]

ive been MIA all week, i know...came down with the stomach flu Wooohoooo! not. I'll do all that homework from the input you all gave me. Im wondering if its something with the drive train. I know the trans has been slipping from time to time.... i smell a transmission probelm coming soon. Shall we make bets? lol

[Skippy1827]

Stomach flu, or SWINE FLU????? I mean H1N1 flu??????. or is it bird flu, or ..

[golfyeti]

ive been MIA all week, i know...came down with the stomach flu Wooohoooo! not. I'll do all that homework from the input you all gave me. Im wondering if its something with the drive train. I know the trans has been slipping from time to time.... i smell a transmission probelm coming soon. Shall we make bets? lol

If you mean the shimmy might be because of the drive train, I'll take that bet.

Try putting it into Neutral while in the "shimmy zone" -- mine still shimmies with no drive train engaged. Even costed in neutral from a higher speed and it shimmied just the same as I coasted down through the shimmy zone.

[1fatcat]

I have very bad rear shocks mounts (somehow connected...who knows)

Lastly, the techincian who replaced my rotors mention that a front tie-rod was a little loose. I haven't replaced it yet but as for the shimmy I'm not sure if hte tie-rod is "cause or effect"...

A loose tie rod end can cause your problem.

Bad rear shock mounts will hurt overall ride quality and contribute to a noisy ride. They are fairly inexpensive and easy to install.

[RookieSSei]

my shake went away when I had my trans rebuild but now lol.. i think they damaged my knock sensor its its giving me a po33 code service engine soon light but it comes on once a week like clock work and goes off for a week ? o well, no More shake and I need tires so I dont think it's your tires

[ptrfair]

Im entertaining the idea of front shocks. Any brand recommendations? Tires are road force balanced.

BTW: not swine flu...however i might have what they call Tapeworm and or an ulcer. wonderful stuff. Ive hardly been by a computer, time to go read last weeks posts. =) Good to be back