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Old 06-20-2011, 08:43 AM   #1
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Need help - steering wheel wobble

Hi all,

I've got a randomly-appearing steering wheel wobble at speed that I don't want to throw money at to track down. I consider myself fairly good at diagnosing these things, but this one has got me stumped and I'm going to start trying things soon.

99 Boxster, 61k miles, about 30k on the 18" turbo twists sitting on there now. Shod in michelin pilot sports (not PS2s). Tires only have about 8k miles on them. Suspension was re-done less than 10k ago with bilstein HDs on stock springs. Alignment was performed at that time and returned to spec. Car went over something (don't know what, was my father's at the time) that slammed into the pass-side front jacking point pretty hard and messed it up, but no other visible damage so I don't see how it could've thrown anything off.

My steering wheel shimmies and wobbles at a variety of speeds. But those speeds are rarely consistent. For the past few weeks, 70-74mph has been very safe...today it wobbled badly at those speeds and went away at 78-80mph. Sometimes wobbles down around 50mph. Usually safe from 0-40 and 56-65mph from all notable shimmy or wobble.

On the same day/drive, it'll sometimes wobble at a specific speed and then stop when I return to that speed 5 minutes later.

I want to eliminate as much as possible before going and getting the tires re-balanced - so I'm looking for tips here. The wheels look great in terms of round-ness, no obvious bends. Tires are in great shape and are michelins.

I've inspected the front suspension and steering BUSHINGs and all look good - actually, they look really great for a 12/13 year old car.

What else should I inspect or examine on this car before dropping $100-150 to get a quality re-balancing done?

Any and all advice welcome.

Joe

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Old 06-20-2011, 09:00 AM   #2
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So this all started after hitting something? Put your spare on the car and see if it still shakes.

If it started after hitting something, it has to be bent rim or bent component.
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Old 06-20-2011, 09:30 AM   #3
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Sorry, I didn't mean to insinuate that. I have no idea when it started. I received the car from my father about a year ago and have been slowly sorting it out (it was in good condition, just a handful of things to take care of).

The one additional factoid I have here is that the issue was still present when I had a set of 17" wheels/tires on for cold weather times - but it was different in severity, speeds, etc.

So either both set of wheels are out of balance somehow, or it's another component.

I'm about 80% sure it's somehow balancing related - the fact that it changed with wheels/tires at all indicates it's related to their rotation. However, if there are things I can inspect first to make sure that's accurate I would vastly prefer too...
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Old 06-20-2011, 10:52 AM   #4
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Well with the new information, I would say it is either the tires, or the bushings.

You can not tell if bushings and tie rod ends are going out just by look/or push pull. The fact that it is older than ten years, I would say that this is the first place to look.

If the tires or rims are bad, then it will not come and go. It will be constant, maybe worse at times, but always there.

Bushings will go slowly, maybe make a rattle noise on cobble stone road at around 10 MPH.
For around 60$ and some time, you can replace the bushings only. Even if this is not the problem, it will be worth the repair.
There is not a lot of choices. Tire/rims, bushings/rotors/bearings. (very rarly it could be the steering rack)

Also a important finding.....Does the shake increase in frequency with speed? Ie: shake faster the faster you go? If it does this, then it is rotational. In this case, if balancing does not work or last, then take the rims to a repair shop to check and repair roundness.

Any spacers?
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Old 06-20-2011, 11:17 AM   #5
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An improperly manufactured/balanced front wheel spacer will do this even if you think it just can't be! It happened to me..
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Old 06-20-2011, 11:27 AM   #6
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Quote:
Originally Posted by jaykay
An improperly manufactured/balanced front wheel spacer will do this even if you think it just can't be! It happened to me..
That'd be a nice place to start looking if there are indeed spacers to keep from pulling one's hair out having gone after a bunch of other usual suspects in the suspension. I'll have to keep that in mind if I ever start using those.
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Old 06-20-2011, 11:34 AM   #7
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No spacers. Rotors are ~10k miles old zimmerman cross-drilled

Shimmy can be as severe at 50mph as at 80mph, but seems to get a bit worse as speed increases above 85-90mph. But perhaps just more constant there. It's not linearly increasing with speed. When it's at its most severe, I'm guessing the steering wheel is shimmying through 5-7 degrees of motion. Like a really badly balanced tire or how the steering wheel will shake like crazy when a rotor is very warped during braking.

I'm gonna focus on bushings at this time. Off the top of my head, I'm thinking control arm bushings (most likely), steering rack bushings (less likely), sway bar bushings (least liklely). Any others? I'd include strut top hats except those should be brand new with the bilstein HDs....hmmm...
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Old 06-20-2011, 11:47 AM   #8
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Okay....try the front track bars. They have rubber bushes in them that will degrade. Unfortunately i think you have to change the whole metal arm. I can dig for a part number if you are not sure what I am talking about...

Perhaps now there are cheaper aftermarket pieces available
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Old 06-20-2011, 12:59 PM   #9
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Front track bars = front sway bars?

Not familiar with that term.

I don't think I'm right there as I've never heard of worn out sway bar bushings causing significant steering wheel wobble. Just noise/clunking. So I'm guessing track bars is something else....? Control arms?
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Old 06-20-2011, 01:19 PM   #10
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No track arms as in orientation of the wheel....suspension arm linkage/control arm

I will have to get you the right name. It could be wishbone as well.

Bushings in
996341043 and/or 996341053 06 (07) (16) (00)
Could be done
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Old 06-20-2011, 02:23 PM   #11
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Rather than guess at parts. Why not have the car re-aligned. During the process the mechanic will check for excessive play or damage in the components.

You can fix the components yourself if thats what you want to do. Usually they will give you a deal to re-align after you install parts if necessary.
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Old 06-20-2011, 05:49 PM   #12
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Yes for sure have a mechanic push and pull on these parts and examine the bushings within. These are the main ones that would cause flutter in the front wheels. It's hard to do without a lift
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Old 06-20-2011, 06:09 PM   #13
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Just trying to prevent a shimmy I've driven on for 5k miles (and is manageable by changing speeds) from developing into a $800 repair - my hope has been I can identify it before starting down the road of paying to identify it.

However, I do have a mechanic I trust.
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Old 06-20-2011, 06:59 PM   #14
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Before you run out and spend a lot of money...

the shaking.... left to right, does the speed of the shake increase with speed of the car?

If it does, it is not the bushings. It is something that is spinning.

On top of that. you can replace just the bushings if you want. You should replace the bushings on a 12 year old car anyway, but that is another topic for discussion.

you can buy them here:
store.powerflexusa.com/porsche-boxster-1997---2004-urethane-bushings-p80.aspx

If a mechanic can push or pull the bushings and it wobbles, then they are badly screwed up and would be knocking and shuddering all over the road.
You can not tell by this method. The tolerances are just too small.
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Old 06-20-2011, 08:25 PM   #15
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My car suffered a bad case of steering shake which took me months to sort out... While I can't tell u exact what your problem might be, I can share the following:

1. It is difficult to diagnose whether the control arm and control arm linkage bushings are bad while they are still installed on the car, unless they are really really gone... Mine was rock solid with no play when my mechanic tested them by lifting up the car and shaking on the wheels and knocking on arms. BUT when they were disconnected from each other, the control arms had a lot of lateral play. The control arm linkage had slight play on them.

2. My outer tie rods looked good too, with no play, but when the mechanic tried to remove them, the ball joint just dropped out of the mounting point on the hub (?) after the nut was removed... no need to press them out.. In my case, changing the outer tie rods had the biggest impact on the shimmy.

Not to scare you but in the end, what I found on my car was:
1. front shocks shaft badly shaking but no leaks
2. front control arms (end bushings) bad
3. front control arms linkage bushings slightly bad
4. tie rod end one side bad
5. front rims badly dented

I now have all new suspension components... I now still have very very slight movement from the steering, maybe my wheel balancing is off, or because I now have 7mm spacers...but very acceptable. I'll be doing the inner tie rods next - more of preventive maintenance and because the new parts have been sitting around for the past 6 months... it's the only relatively cheap and easily renewable part in the front suspension/steering component left my car !

These cars are very sensitive to slight imperfections in the suspension/steering components !

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Old 06-21-2011, 03:10 AM   #16
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Quote:
Originally Posted by JoeFromPA
Just trying to prevent a shimmy I've driven on for 5k miles (and is manageable by changing speeds) from developing into a $800 repair - my hope has been I can identify it before starting down the road of paying to identify it.

However, I do have a mechanic I trust.
That's great that you've got new shocks, but I'd be willing to bet that you've got worn bushings in more than once place. You've got a 12 year old car, so plenty of rubber components are due to be replaced.
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Old 06-21-2011, 07:06 AM   #17
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Yikes - looks like this is going to be my winter 2011 job. 2010 was spent tuning the car up, replacing all the fluids, and replacing the motor mount.

Now I've got a rattling heat shield (easy), squeaky rear brakes (easy), a horn that stopped working (we'll see how easy), and the front end shimmy (ugh).

I'm almost certain this is bushing related at this time. I took the car up to ~105mph yesterday on an extremely clear, flat section of (track) roadway in great road surface condition. The car actually felt great from 85-105 and had more shimmy at 70-80mph. It's not distinctly rotational in nature, though it tends to be harshest when it kicks in at the higher speeds. Bushing-related shimmy makes more sense considering sometimes there's no shimmy at a speed and other times it's more severe.

Further, I believe the reason the shimmy changed in nature when I switched from my winter to summer wheels/tires is because the winter rubber has different dimensions and absorbed more wiggle - whereas the michelin pilot sports are far stiffer and will twitch more by their stickiness.

I'm going to focus on the front end at this time since that is what will cause steering shimmy. I'm thinking I should tackle it like this:

1. Replace front track and control arm bushings (inner & outer)
2. Remove, inspect, and possibly replace outer tie rods
3. Remove, inspect, and possibly replace inner tie rods

Stop there and examine shimmy - if dramatically different, get the car re-aligned and call it a day.

If it called for replacing both tie rods, and I did all the work myself except I took the control arms to my mechanic to get the new bushings pressed in, I'd expect this all to come in under $500. Tie rods are around $100 for both inner and outer on pelican parts. The bushings are about $170 from powerflex (which is also sold at pelican parts as the only full rubber replacement bushing.

So that's $270 - figure $50 for pressing the bushings in, $100 for the alignment, and $80 for miscellaneous tools (like a tie rod end puller) and random parts.

Yep, $500 for a freshened up front suspension and steering. Yikes.

Might also be worthwhile to drop another $100 at that point and have the tires rotated laterally and re-balanced. One more area to get rid of shimmy, and might be worth $100 to extend the tire life that much....
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Old 06-21-2011, 11:57 AM   #18
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90% of the time your steering wheel shimmys at some speed but not others, it is caused by imbalance in the wheel/tire assembly. Rear tires affect the rear of the chassis & vibration can be felt in the seats. OK to check for wheel/tire imbalance remove other variables by setting tire PSI to vehicle manufacturers cold spec. Drive car on highway 5+ miles to get tires warmed up to operating temp. Now drive car to the smoothest, flatest road you can find. Any steering wheel can jump around if the road is rough enough. Drive at varing speeds to test for vibrations (I do this after any tire work/balancing to insure work is done properly, at night when it's quiet) 60-75mph seems to be the most critical speed. This establishes your baseline, if you have vibration on a smooth road you have a problem that needs to be resolved. When your tires are being balanced, WATCH to see it's done properly, Hi-perf tires on Porsche wheels should not require more than 2.5oz to balance. Watch the wheel spin on the balancer, if it hops up & down the wheel is probably bent & will hop up & down on your car too. If you see this ask them to remove the tire & spin balance the bare wheel to see how far out of balance your wheel is. I try to have this done before the tire is installed the first time so I know the condition of my wheels.
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Old 06-23-2011, 04:31 AM   #19
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Joe, please keep us (ME) posted. I have literally the EXACT issues.

It was really bad last summer. I replaced an outer tie rod, wheel balance and alignment. It got WAY better, but not where I want it. I am thinking bushings for me. I will also replace the other outer tie rod while i'm in there.

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