Need help - steering wheel wobble - 986 Forum - The Community for Porsche Boxster & Cayman Owners

JoeFromPA · 06-20-2011, 08:43 AM

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

jhandy · 06-20-2011, 09:00 AM

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.

JoeFromPA · 06-20-2011, 09:30 AM

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...

jhandy · 06-20-2011, 10:52 AM

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?

jaykay · 06-20-2011, 11:17 AM

An improperly manufactured/balanced front wheel spacer will do this even if you think it just can't be! It happened to me..

Overdrive · 06-20-2011, 11:27 AM

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.

JoeFromPA · 06-20-2011, 11:34 AM

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...

BYprodriver · 06-21-2011, 11:57 AM

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.

greenerob · 06-23-2011, 04:31 AM

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.