Sudden shimmy shake

[Not Stig]

I took my 87Targa out for a drive after sitting due to the pandemic lockdown. I drove on the freeway for about an hour and the car ran perfectly, nice and smooth. On the way home I was entering the freeway onramp, a sweeping right hander at about 35 MPH when the steering wheel began to vibrate and shimmy. I thought it must be the road surface and continued onto the freeway. On the freeway the vibration and shimmy continued so I thought I must have a tire going flat. I pulled off and checked the tires and they were fine. I did not hit any potholes or curbs during the drive. On the drive home I noticed that he shimmy shake stopped when turning to the left and then started again when going straight or turning to the right. When I got home I checked the following.

Tire Pressure, OK
Wheel weights, all in place
Lug nut torque, OK
Tire damage, None, no blisters, good tread, 10 years old, 9000 miles
Wheel bearings, very slight amount of play on right front

Help! What should I be checking next!

[Rodney Nelson]

I would check those tires again. This happened to me on a set of 10 year old tires with about the same amount of wear, or maybe even less, they looked brand new. I was on the freeway and then all of a sudden the shake started happening. I thought it was the road too. Then when I slowed down it was not there anymore.

Then a week later I was on the freeway again and I noticed it. Then it started to get worse and worse. I pulled over and could not find anything wrong with the tires or suspension. I was in the middle of nowhere and had to call AAA. While it was getting loaded on the flat bed the driver said here is the problem. It was one of my tires, in the middle a blister. Of course I was parked right on it when I was doing my inspection.

Pulled the car back off installed the spare and ordered a new set of tires. What they say is true. 10 year old tires need to be replaced even if they look brand new.

I would mar your tires and inspect, roll a bit, inspect, roll...

of course a shimmy at a certain speed can also be a wheel balance issue.

I would replace all of the tires have everything balanced and see if the shimmy goes away.

my .02

[icarp]

Sounds like a belt shift on one of the treads . New tires will fix that
Ian

[mike sampsel]

Probably not your issue, but my shimmy which was pronounced at straight driving turned out to be a weak ball joint. Around 97 K miles I replaced mine, and no more shimmy!

[JSV798]

10 year old tyres on my car started to delaminate giving rise to vibration that was hard to spot until I had a really good look at the rear tyres. So suspect tyres delaminating.

[wildthing]

10 year old tires... I'd replace them.

[Reiver]

You need new tires anyway so go that route of elimination...... prob the issue

[Flojo]

Originally Posted by Not Stig

Tire damage, None, no blisters, good tread, 10 years old, 9000 miles

dear God! a street sport tire hardens at about 5-6 years.
get new ones asap!

Originally Posted by Not Stig

Wheel bearings, very slight amount of play on right front

a minimal play is OK. but the feel shoulb be in spec 1:1 for left and right.

[Not Stig]

Thanks for the great advise, based on age the tires should have been replaced year ago. I will replace the tires and report back.

[creaturecat]

should be some tire obvious damage, if it happened in a matter of seconds. no?
a balancer would indicate problems if it's tire-related shake and shimmy. no?
you check control arm bushings, etc?

[shoooo32]

I'm guessing a loose wheel bearing. It doesn't take much to give you a shimmy.

But yeah, get some fresh skins asap. 10 year old tires are toast no matter how much tread.

[Not Stig]

First let me stipulate that I know I need to replace the tires due to age. Now for the mystery. When I checked the wheel bearings, I noticed a small amount of play on the right front wheel. I grabbed the tire at the twelve and six o'clock position and was able to rock the wheel slightly. I decided to check the wheel bearing adjustment, so I removed the wheel and the dust cap and tried to move the thrust washer with the tip of a screwdriver. It took quite a bit of effort to move the thrust washer so I assumed the bearing adjustment was OK and the play must be somewhere in the suspension. I reinstalled the wheel and tried rocking the wheel to see if could see movement in the suspension. The play was completely gone. WTF! No, the wheel was not loose. I had checked the lug nuts with a torque wrench before and after I removed the wheel. I decided to go for a drive to see if the shimmy continued and thought to myself it's wishful thinking that the shimmy was somehow cured by taking the wheel off and putting it back on. Guess what? The shimmy shake was completely gone. Since then, I've driven the car for hours on all kinds of roads at different speeds and no shimmy shake. Can anyone solve the mystery for me?

[rosecarl]

Perhaps ensure your upper steering column bearing has not disintegrated?

[Superman]

I wonder if a worn ball joint could do this, or a worn tie rod end.

[kltarga72]

If you do not have access to a lift take it to a good tire alignment shop and have them inspect for worn ball joints, bushings etc.

[cabmandone]

Originally Posted by Not Stig

First let me stipulate that I know I need to replace the tires due to age. Now for the mystery. When I checked the wheel bearings, I noticed a small amount of play on the right front wheel. I grabbed the tire at the twelve and six o'clock position and was able to rock the wheel slightly. I decided to check the wheel bearing adjustment, so I removed the wheel and the dust cap and tried to move the thrust washer with the tip of a screwdriver. It took quite a bit of effort to move the thrust washer so I assumed the bearing adjustment was OK and the play must be somewhere in the suspension. I reinstalled the wheel and tried rocking the wheel to see if could see movement in the suspension. The play was completely gone. WTF! No, the wheel was not loose. I had checked the lug nuts with a torque wrench before and after I removed the wheel. I decided to go for a drive to see if the shimmy continued and thought to myself it's wishful thinking that the shimmy was somehow cured by taking the wheel off and putting it back on. Guess what? The shimmy shake was completely gone. Since then, I've driven the car for hours on all kinds of roads at different speeds and no shimmy shake. Can anyone solve the mystery for me?

You didn't happen to do brakes on the front and pump the brakes before you had torqued the wheel did you? I don't recall how the 911 rotor is held on the hub but I've seen guys get the rotor out of whack by not installing the wheel and at least tightening it before pumping the brakes.

Originally Posted by Superman

I wonder if a worn ball joint could do this, or a worn tie rod end.

Pretty much a yes to both. And both can have the same feel as a worn wheel bearing. You need to have someone watching as you wiggle the tire to make sure it's the wheel bearing or a ball joint/tie rod end issue. I made the mistake of changing a wheel bearing only to find I needed to replace a ball joint once.

[GH85Carrera]

Originally Posted by Reiver

You need new tires anyway so go that route of elimination...... prob the issue

This! 10 year old tires are not a good idea. Think about it, the ONLY contact the car has to the ground is the little patch of rubber of the tires. Old tires can look perfect, but have lots of problems. I bet one (likely a front) has a delamination or bubble in the rubber. Take the wheels off, and inspect both front tires. You might find the issue. Order new tires anyway.

And drive your 911 more! I never have old tires as I wear them out before the get old. I have 182,000 miles on my 911.