Front End Shimmy

[rcecale]

I've been noticing lately that I'm getting a shimmy in my front end. It starts coming on at around 50 MPH and gets worse at 60. By the time I get to 70, it's pretty much gone. It's not a real drastic shimmy, but it is enough to make the steering wheel shake quite a bit.

I'm not sure if this is related, but I think it is...I also have been experiencing a pull to the left when coming to a stop, although I don't get this all the time.

I've asked my mech and he seems to thing it could be flat spots in the tires since I had her sitting in the garage for quite a while, but I've been driving her pretty regularly since September. I'm thinking that it's most likely something else.

Anybody have any ideas?

Randy

[speeder]

Sounds like a tire-related problem, (could a large wheel weight have fallen off?), but I would raise the front end and just start checking everything down the line, tires, wheel bearings, (not too loose), tie rods/ball joints, (major suspects), etc...

Good luck!

[surflvr911sc]

Denis beat me and is right on. Almost all shimmy problems are a tire problem; flat spots, out of balance. Shocks would be the second place I'd look, are they original?

[rcecale]

Thanks for the replies, felas! Looks like I have my work cut out for me.

I don't have access to a lift, so I thinking I'll have to do the physical check one side at a time. Am I just looking for anything that is noticably loose, or is this gonna be a bit more involved than that?

Randy

[avi8torny]

I remember the last time I replace front rotors and pads my shimmy went away. I was chasing the tire balance all along and it turned out to be a worn set of rotors. FYI

[oneblueyedog]

I had a shimmy once like this. I tried balancing tires. I tried new inserts. It turned out to be the ball joints on the a arms.

Do you have suspension squeaks in the front? This was alsoa symptom.

Ball joint replacement trick- cut the circular nut off. I had to use fiberglass reinforced cutting wheels, and an air chisel. I made the 2 cuts on each nut 180 apart. The special tool will not remove it. It's an intallation tool. I tried and it deformed the tool.

When you tighten it you have to place a jack under the tool and torque wrench to keep it squarely against the new circular nut. It's at a huge torque rating. 4 tangs are all that twist the circular nut. It slips off easily. I enjoyed dropping the engine a lot more than this job.

I hope its just a tire prob.

[rcecale]

Well, I thought I was on the right track. First glanced showe me that I was missing the balancing weight off my left front tire. Then I took a look at the right...again, no weight. Heck, all 4 tires were without wieights.



This had to be it....wrong!!! Closer investigation shows the weights were installed on the insides of the wheels. All 4 wheels have them. Could still be outta balance, I suppose, but I'm thinking it's something else.

I've got no squeaks coming from the front end. Or from anywhere, for that matter...unless you count the squeaks from my Targa, but I'm positive that's not the problem.

Randy

[74-911]

I had the same problem. The easiest way to determine if the problem is tire balance/out of round is move the front tires to the rear. If the shimmy persists, you have a suspension problem of some sort. If the shimmy goes away (is moved to the rear), you have a tire out of balance most likely.

When I rotated the tires, the shimmy went away. Had the 2 now rear tires balanced and all was smooth.

Jack

[rcecale]

Think I'll try rotating the tires tonight...or some day this week. Supposed to be rainy all week and then clear on Friday so i won't be able to check out any changes till then. I'll also check for anything noticably loose while I have the wheels up in the air.

Thanks for all the ideas!

Randy

[Jdub]

Check the PSI, front and rear. Have the tires balanced anyways, things change. Bring it to a Porsche independent and get him a 12-pack of good beer to do a simple lift and check -- will take him all of ten minutes and you have made a friend. You really cannot be sure you know enough to know what to look for, no insult intended.

John

[rcecale]

No offense, taken Jdub, you're 100% correct, I really don't know exactly what I'm supposed to be looking for. My wrench has told me at one time that he suspected flat spots.

If they ARE flat spots, will they eventually go away, or am I stuck with this until I get some new tires? Man, that's gonna suck, since the tires have very low miles on them....hate to think what I may be messing up by leaving it like this. And I certainly don't wanna spring for a new set of shoes if that's not the problem, so I'm trying to rule everything out that I can.

As far as tire pressure, I've been checking that out lately and have even been doing some experimenting with different PSI's but the shimmy is always there.

I'll look into a lift and check this weekend, if rotating the tires doesn't help.

Randy

[Erakad]

Funny thing, mine does exactly the same thing. I suspect an alignment problem as the tread is pretty much gone on the insides of each front tire. Having it aligned and new tires put on Friday...will see if that does the job.

[fredmeister]

I would bet a 6 pack that it is your front wheel bearings being too loose. You noticed a pull under braking as well as the shimmy, that indicates wheel bearings. I had a similar problem and after adjusting the bearings a little tighter, things cleared up. The rotor could contribute to the shimmy if it is warped, but you would notice a real vibration under braking then, but you noticed just a pulling sensation which strengthens my suspicion on bearings. Repack them and readjust....couldn't hurt anyway.

[rcecale]

Just discovered something kinda interesting. While checking out my tire sizes, I've determined that the tires on the front are bigger than the rears. Definitely time for a rotation!!!

215/45ZR17's up front and 215/40ZR17's in the rear. While I'm sure this has nothing to do with the shimmy, I do wanna get these swapped around as soon as possible.

Fred, I'll have a look when I'm swapping the tires around. Hopefully it's as simple as re-packing and tightening the bearings.

Randy

[surflvr911sc]

But what size (width) wheel are they mounted on?

Those sizes are screwy though.

[rcecale]

From what I can tell, they are 7.5JJx17 on the front and 8.5JJx17 on the rear. I'm ready for the lesson!!!

Randy

[speeder]

Randy, I would think that you would want larger (numerically) tires on the rear w/ those rim sizes, maybe 245s(?).

At any rate, I doubt that you have flat spots. How long was it ever sitting w/o moving an inch? In the future, it's a good idea to take the weight off of the tires if storing the car, but I have rarely seen flat-spotted tires on a car.

It sounds like a pro balanced the tires last time, at least he didn't put weights on the outside of your nice rims. That's a no-no w/ alloy rims, unless it's a truck or something.

Once again, you need to go through it systematically, eliminating things. Guesses are all good and fine, but not really the way to diagnose things. Good luck!

[rcecale]

I agree, Denis. Gonna have the front tires moved to the rear wheels and vice-versa.

I pass a tire store on the way to work so I'll stop in, drop her off and have them check out everything else while they have her up in the air.

Pro or not, I like the hidden weights, so I'll be sure to stress that when I drop her off. Love the clean look!!!

Randy

[rds356]

Randy,

Have your main wrench check the steering rack for play.
I had a similar shimmy on my 911. We ended up replacing, struts, tie rods ,performed alignment and balancing. Nothing worked until a real sharp mechanic diagnosed a worn out steering rack.

[rcecale]

YIKES!!!

A New Steering Rack??? Sounds expensive! I'll keep that in mind, but I'm hoping it's something a lot less expensive!!!

Randy