Steering wheel shaking at 75+ MPH
 

Hey everyone -

I'm now starting year 2 of the steering wheel shake saga... Anyway, the most recent thing I did has improve the issue significantly (maybe 75% gone now) but I still have this infuriating shake in my steering wheel at 75+ mph and a lot of bump steer / some play in my steering.

Car is 2002 S with 88k miles.

I have replaced all of the following items in search of this issue:

Tie rods (in & out)
Drop links (front)
Struts & Strut mounts (front and rear)
Control arms (front and rear)
Front tracking arms
Rear trailing arms
Wheel bearings (front)
Tires (Continental ExtremeContact DW)
Sway bar bushings (front and rear)
Multiple alignments
Multiple tire balances

All parts are OEM.

Most recently, I went to a Porsche dealer and had them align the car and balance the front wheels. The toe was set to toe out on both the front and rear which they then corrected to zero toe in on the front and slight toe in on the rear.

I'm really at my wits' end here. What else could I look at? I have thrown a ton of money at this issue and I just want to enjoy my car again.

Pretty much every shop I have taken it to has claimed it to be wheel balancing, and I have had the wheels balanced probably 5 times all on Hunter Road Force machines. Every time they balance them, they seem to be close to a 1/2 oz out of balance - is it possible that there is something inside my tie that is causing this? This issue started with my old tires and has continued with the new ones too. I've had multiple places check the rims for bends, but nothing has been noticed - only thing I can think of is that they have not checked the rims with the tires off. I have also tried different PSIs and swapping tires L/R.

Rotors have a pretty significant lip on them, but the vibration does not get any worse when braking. The vibration does seem to get a little bit better as the car warms up... any help would be awesome guys.

Here's yet another possibility. Does your car brake smoothly? If not, the problem could be sticking calipers. I had that problem on one of my cars and was able to get some rebuilt calipers, which solved the problem.

Have you tried putting on a different set of rims AND rubber? If you put a completely different set of rims and rubber, and still get the steering wheel shake.... then you have at least ruled out one element.

Good luck!

Depends on how you define smoothly. In terms of vibration, there is none when I hit the brake. However, the brakes squeal quite a bit. There is a significant lip on my rotor. They seem to drag a tiny bit when I spin the wheel when the car is lifted on jack stands, but not anymore than I think is normal.

Try another set of wheels and tires and see if it still does it. Find a friend with a boxster

Not to put too fine a point on it but the tires are not "OEM". That is I don't believe those tires are factory sanctioned tires with the N rating. However, I read you have experienced the behavior even after new tires so it is unlikely the problem is tire related.

My WAG is one or more wheels is bent slightly -- though this should come out if the wheels/tires are load force balanced -- or one (or more) wheels do not fit property. The wheel is not quite centered and at speed this makes itself known with vibration. Aftermarket wheels are more likely to have some hub concentric issues than factory wheels.

Another problem can be a bad shock. If the shock is bad it can't keep the wheel/tire in contact with the pavement and the assembly will go up and down. The car's ride height will not change when this occurs but if you could observe the car going down the road one (or more) wheel/tire sets would be going up and down like a basketball being dribbled at a fast clip. This is felt in the car as a "vibration".

(Occasionally I'll spot a vehicle with one or more bad shocks. If both sides are bad the front (or rear) of the car will porpoise up and down. I get motion sick just seeing this. Or if just one shock is bad I'll observe the wheel/tire going up and down at a fast clip like the car is being driven on a rippled surface.

If the rotor lip is 1mm the rotors are worn out and should be replaced. Since the brakes are in need of replacing before you do anything else do a brake job: new pads, rotors, and other hardware; and be sure the hub face the rotor hat bolts to is flat, free of any burrs, rust, etc.

Last but not least be sure of tire inflation pressures. My 2002 Boxster manifested a mild vibration at highway speed when in experimenting with tire inflation pressures I over inflated the front tires by just a few PSI over the 29psi (cold) inflation pressure. Get a good/accurate tire pressure gauge and set all tire pressures to the correct cold inflation pressure.

I agree with Macster... I believe it's a wheel that is not perfect. I've experienced this personally. All the balancing and tire replacements won't promote a smooth ride if one of the wheels are not straight.

I would have a shop check the runout on the rotor.........tightening lug nuts with an airtool is a bad idea, lug nuts need to be torqued to spec or over time a rotor can become warped,.

I assume you're talking about impact wrenches? IMHO, it all depends on the application. Impact wrenches are all about speed. That's why pro shops and track crews use them all the time. Most of the professional impact wrenches have built-in torque regulators to prevent over-torquing. But if you're worried about getting exact torque on lugs, then a proper torque wrench is your tool.

Trying another set of wheels will certainly be a good idea - but brake rotors can easily cause this. Even if you are not getting vibration on braking, and if the rotors look clean, build-up on the rotors can cause vibration like this. I have had this exact issue - got the rotors turned and it completely went away.

Inexpensive to have them turned - anyone with the right machine can do it. That or put on new rotors. Pad build up, even slightly can cause this to happen.

Geez. Trying another set of known good front wheels costs nothing but the time to swap the wheels

Ok so today I found a friend with a Boxster who let me borrow his wheels - problem still there. However, when I was putting my wheels back on, I noticed that my front left rotor was much hotter than the other three. To double check, I drove home and then immediately pointed my IR thermometer at all 4 rotors - saving the suspected hot one, the driver left, for last - the other three were between 85 and 90 degrees F, while the driver left was at 115-120 F - could this be indicative of what you mentioned?

Is it possible for rotors to become "unbalanced" as they wear? I've always used a torque wrench for lug nuts and set them to 96. My pads have plenty of life left, but the rotor is of an unknown age as I do not have anything from the previous owner saying they have been replaced.

Hey Mac, thanks for the incredible detail in your answer. Thanks for the info on the tires - I was unaware of the N rating when I bought them, the shop I purchased them from said they were popular with Porsches so I did not inquire much further. I've had the same thought about the rim being bent, but all the people who have put on a road force balancer have been unable to detect this. Also, today, I borrowed a set of wheels from a friend and did not notice any improvement.

However, as I mentioned in another reply on this thread, when I was swapping the wheels back with my friend, I noticed that my driver-side front rotor (the area which I suspect the vibration is coming from as my side mirror seems to vibrate rapidly) was significantly hotter than the other three. I drove home - about 40 miles with little braking, mostly freeway - and checked all rotors against using an infrared thermometer. I saved the suspected one for last to make sure that it was not that the other ones had cooled more, and found that three others were 85-90 F, while the driver left was at 120 F. Could this been warped rotor or a caliper issue?

That sounds more like a stuck piston in your brake caliper or some other issue which would definitely cause this vibration issue. Before I had my rotors turned I thought I had the same issue - and did exactly what you did to see if I was getting any hot rotors. I'd bet anything that is your problem right there.