SimonK

I can’t dial out a slight shimmy on my car no matter what I try. The shimmy appears at 75-85mph and it shimmies the steering wheel only slightly at about (1mm) left and right.

I had my wheels on car balanced, I had my wheels checked, I had bearings checked and suspension perfectly aligned to no avail. It does not shimmy when braking.

The suspension alignment guy tells me it’s my Pirelli P0 Rosso tyres as they flat spot all the time. I call it bull**** as I always had this shimmy problem, with the Bridgestone Potenza So2’s as well.

So, I thought once and for all let’s discuss the most common causes of shimmies on our cars excluding the above mentioned ones and anyone who cured it please chime in with the success story and the cult prints.

Let’s go…

billthe3

Mine was bad balanced tires. Once they were balanced the problem went away.

At least it did until I locked up the front brakes on the freeway (god damn traffic) and then it came back because of the flat spots.

RKD in OKC

It doesn't take much out of balance at those speeds to shimmy.

When I had my boxster I added some fancy valve stem caps with the Porsche logo and it was enough to cause what you describe. I had to have the wheels/tires rebalanced with the fancy caps to kill it.

Luis de Prat

Can't hurt to check a-arms for loose ball joints.

Also, do you have updated 968 caster blocks, or do you have the the 944 kind with big rubber bushings? You may have a busted bushing.

dacula951

What about the wheel locks? It's only a hunch of mine right now, but it seems like when I leave my wheel locks off there is little or no shake. When they are on I sometimes get some shimmy. I need to determine if there is a difference in weight between the wheel lock with it's lug nut and an ordinary lug nut (aluminum ones).

lejams

Have you tried having the wheels balanced, and then high speed balanced on the car?

turboted

My first guess would be the tires...but since the shimmy didn't go away when you replaced the tires, it's pretty safe to rule this out. Especially considering you road-force balanced the new rubber.

It could be that one of your wheels is slightly out of round...or barely bent. What size are your wheels, 16, 17, 18"? You said you had the wheels checked...who checked them and how did they do it? Are you 100% SURE that your wheels are straight/true? Wheels should be checked for straightness while mounted on the car...and run out should be measured with a dial indicator radially and laterally on the inside and outside surfaces of each wheel. Larger diameter wheels are much easier to bend than many people realize.

Also, is your car lowered? My old IS300 shook like crazy...and after replacing tires, wheels, bushings, etc., I finally concluded the car was lowered too much. I raised it up about a 1/2 inch (had adjustable perhces) and the shimmy was gone. It was an issue of supension geometry in this case. Too bad I spent so much $$$$$ before I figured this out.

dime1622

The solution is to just drive 95 mph where it goes away.

When my wheel weights fall off I have shimmy at 70-80 mph.

waynelambright

I have the shimmy from hell.

1989 944 turbo, 166K Porsche twist 17" wheels. New tires 4000 miles. HOT Tire Pressure 45 PSI.

I bought the car on ebay in July 07, few to PA and Drove home to San Francisco. The tires were about 1000 miles old, and there was really no shimmy at that time. I did have slight pull to the right. About 1500 miles into the drive, I noticed a small slight shimmy about 30 mph.

Explanation of the shimmy: I get 1 inch left & right steering wheel gyration 2” total travel, its really scary. It feels like the wheels are going to jump off.

The shimmy is defiantly speed & road surface related.

What I have done so far.

1. Checked control arm ball joint for play. I jacked car up, put large channel locks and squeezed, maybe I see 1mm of play, it’s almost undetectable. One rubber boot has a crack the other is intact, the mounts have red rubber bushings, which makes me suspect that the control arms were replaced a while back, they look like there in good shape.
2. Adj Wheel bearing 12/6 positions, each needs about 1/3 turn. Results, tighter feel, shimmy still present.
3. Wheels balanced, “OFF CAR”. Shimmy still present.
4. Adj Tire pressure “HOT” to 40, was less noticeable, when to about 37psi it was even worse, about 45/50 mph. Put back to 45 PSI.
5. Check tie rod for play, there is a slight amount, but I doubt it would cause this crazy steering wheel shimmy.

Any thoughts?

Thanks for your help.

Wayne Lambright
415-750-1921

Cory9584

is the rack in there tight?

PorscheMD

If the shimmy happens at a certain speed and you can drive in and out of it. You need to have your tires rebalanced somewhere else....

shiners780

I've heard of this. They put the wheel lock nut on opposite the valve stem to counter-balance eachother. Truth or bunk...you decide. Sounds plausible though.

BlacknRedGT

Sounds like a mythbusters episode.

dand86951

Do you know for certain the alignment was done correctly? If you have very close to zero toe in it is easier from a harmonic standpoint for the tire to go into an out of balance. I have found the toe in to have an influence and have also found that when I take the tire back in for re balance and tell them to make absolutely certain there is zero out of balance at 100mph the shimmy has gone away.

I have also had it happen when the tire looked good and balance and alignment were spot on, but in fact had an internal belt problem, new tire and presto no shimmy. Living in the cold country I notice that my car an '86, will usually have some shimmy until the tires get warmed up even though the tires feel like they are round and run smooth. Just another indication how critical the roundness and balance are in my opinion.

Porschefile

Lol. Awesome!

Here's a check list:

-Steering rack bushings
-Tie rods
-Control arm bushings
-Castor blocks
-Wheel bearings (that's a long shot)
-Strut/Upper strut mount condition
-Toe settings

That's all I can think of. I've had several different shimmy's like this. The last on my 951 turned out to be a bit too much toe out and a pretty decent amount of negative camber up front. The reason that caused it in my case is moving at highway speeds and over rough surfaces, lots of toe or negative camber can really cause the wheels to track the road. In a friend's 951, he had a similar issue that was exacerbated by the fact his struts were blown, so the car would bounce around off the bump stops and cause all kinds of funky alignment issues, which was amplified horribly at speed.