PontiacBonnevilleClub.com

With the notorious 65-75 front end shimmy with this 2000-2005 car, I'm wondering if one cause is basic manufacturing loose tolerances resulting in unbalanced wheels/not round wheels, for the stock wheels used for the Bonnevilles. Heaven knows everything under the sun has been tried on the suspension parts, with very spotty results. If you have or have had the front end shimmy, has anyone just simply replaced the wheels with aftermarket wheels, with new tires with a good balancing job and front end alignment, and that resulted in absolutely no improvement in the shimmy?

When I bought my car it had afrermarket rims on it. I rotated the tires thinking that would help and it did not. So, I went and found another ssei that had no shimmy. Took the rims and tires off it and put them on my car, still had the shimmy. I personally think its in the transmission. But I wont know for sure until I have it rebuilt later this year.

Good luck.

There's a reason we balance wheels and tires, because they aren't perfectly round or weighted. They have to meet a certain spec to get on the car, and unless you run over a curb or somehow bend one, that really isn't going to change. If you want to eliminate your wheels and tires completely from the shimmy, have them road-force balanced.

torero500 wrote: If you have or have had the front end shimmy, has anyone just simply replaced the wheels with aftermarket wheels, with new tires with a good balancing job and front end alignment, and that resulted in absolutely no improvement in the shimmy?

Yep I have, my brand new after-market wheels and tires (shown below) did not change the shimmey one bit. Had my swoopies and RSA balanced many times, including RoadForce balanced too. No change. Changed all bushings, control arms and hubs. Have not changed CVs or front struts.

I get the shimmey say between 62 -65 mph into a headwind but turn around and I only find the shimmey range between 65-71 with a tailwind. This has been verified many times.
No matter how much faster you go the shimmey does not re-emerge as I would expect from unbalanced tires.

It's matter of a certain "play in torque resistance" at cruising speed.

Question: Does the CV joint or drive shaft have a torquable rubber compenent (I'm thinking like a worn u-joint on a rear wheel drive)? One who's torque resistance might fluctuate at a certain medium-low torque level like that found at a certain (wind resistance) hwy cruising speed? I hope you get the drift of what I am asking.

The only observance I had that may contradict the above theory is that if you go into Neutral at say 75 mph and coast down through the shimmey zone speeds the shimmey will occur (drivetrain disengaged).

Last guess, worn or bent drive shaft?

i was without shimmy for a good long time, however it has returned just not as bad. funny as how the front and rear trans mount are bad again! im thinking a correlation between the two.

2003BlackSaphire,

try this where you won't get a speeding ticket...

if you go into Neutral at say 75 mph and coast down through the shimmey zone speeds the shimmey will occur (drivetrain disengaged).

If this occurs for you too then this eliminates motor mounts as the drive train is not engage.

So my question now is, other than wheels, what is still rotating while in neutral?

Or is this perhaps an aerodynamic issue, which was my very first suspicion, bad air dam design or bad aerodynamics of the wheel well or the coke bottle body design of the 2000+ style. If I replace the CV and struts and the shimmey is still there then I'm chocking it up to bad aerodynamics at 63-69 mph.

My car will shimmy with car in neutral at 75 mph.

Lots of parts inside the trans are still spinning in neutral, it's just that the gears aren't engaged with the input shaft.

Update: Finally broke down and bought 4 new tires last weekend at discount tire. The cheapies, $86 Falken label from cooper tires. Around town no more front end vibration, softer ride, and at quite fast highway speeds just the 4 new tires eliminated about 95% of the total front end vibration I used to get at 55-75. There's still a tiny bit in the passenger's seat, but the steering and dash now have dramatically less shimmy. There are actually long patches of complete vibration free driving. About the only other front end suspension work I've done on the car is new rotors and brake pads, and new inner tie rods.

So in conclusion, putting new tires on, among the most obvious of solutions, can work.

torero500 wrote:Update: Finally broke down and bought 4 new tires last weekend at discount tire. The cheapies, $86 Falken label from cooper tires. Around town no more front end vibration, softer ride, and at quite fast highway speeds just the 4 new tires eliminated about 95% of the total front end vibration I used to get at 55-75. There's still a tiny bit in the passenger's seat, but the steering and dash now have dramatically less shimmy. There are actually long patches of complete vibration free driving. About the only other front end suspension work I've done on the car is new rotors and brake pads, and new inner tie rods.

So in conclusion, putting new tires on, among the most obvious of solutions, can work.

I had a horrible virbation also - it was time for new tires and after I got 4 new tires, alignment, balance I had the same result - 99% of vibration gone at 55-75 and most times no vibration.

My vibration stoped when I fixed my transmission.