Nasty Shimmy and Shake...
 

I have a 99 Boxster with 30K miles. She has been absolutely perfect, until yesterday. Over 60 MPH, the car felt like it was a paint shaker. Anyone have any thoughts on what it is? I apologize if I should know this, but I am new to the site and new to owning a Porsche (6 months now). Thanks for any help.

At the very least, go out and check your lug bolts. Also, you may have thrown some wheel weights - hit any potholes lately?

Can you isolate where it starts first?.... front, rear, etc.

good luck,

kj

The man is right about checking the lug nuts, but also check them for correct torque and not just to see if they are tight. Correct torque is imperative if you want a safe and wobble free ride. Ed

Thanks. Lug nuts are tight and wheel weights are there. I didn't check the torque. The shake is so bad it is hard to tell if it front or rear, but I'd guess rear.

Just to rule out your wheels and tires, get them road force balanced on a Hunter 9700 series machine. Many Discount Tire shops have them, but some don't so ask. With this machine, they have the ability to see the heaviest part of the wheel and the lightest part of the tire and match them to make the unit more balanced without weights.

If after you've done this the car is still shaking like crazy, a Porsche mechanic (dealership or indy) needs to inspect the car and drive it. He can then tell you if one of your wheel bearings is shot or not, which can cause bad vibration. My car had a horrible vibration problem that I could never fix with wheel balancing. I changed out the wheel bearings all the way around and it rides like a brand new car now.

These are the things that spin and cause vibration at speed. Another thing to check is your motor mounts, but frankly, they degrade over time and don't crap out on you overnight like what you are describing.

If it's a bearing, you should find a good indy shop to do the work for you. The dealership will rape you. The part is only $50 but the book rate for labor is something like 4-6 hours. An indy might just charge you actual time.

Great tip. Thanks. I might just swap the wheel bearings as you suggested. I have new Sumi's coming this week and I'll see if they use the Hunter. I have heard from many people that the Hunter is the best way to balance. I'll advise later this week if that worked. Thanks to all. This is a really great site and everyone is extremely helpful.

I suppose a wheel bearing could be the culprit, but that would have to be one bad bearing (and you'd probably be hearing a drone or dull whirring sound).... as a sanity check before anymore freeway driving, jack up each corner and grab the top and bottom of each tire and push/pull hard to see if you can detect any play from the hub (also known as 'wheel bearing carrier').


good luck,

kj

Ah ha! I couldn't tell by the way I was parked before, but now I see the OBVIOUS problem. My PS Rear Tire is canted about 5 degrees toward the top. Something broke... Great! I'm sure it will be inexpensive. (sarcasm)

It'll depend on which link "may" be broken.... possibly an eccentric adjustment has come loose and a realignment may be all that's needed - hope for the best.

If it's a link, it should be pretty straight forward to replace and realign.


kj