Vibration At High Speeds

[onlineformals]

I am new to the board and new to the Porsche family.

I have a 2005 Boxster S (987) with 15K miles.

I have found a great independent here in Virginia Beach that has looked after my car for the past few months of ownership.

Did an oil change, new tires and water pump (mine failed)

Quick question here-

I am getting some steering wheel vibration (shimmy) at about 65 MPH. I had the independent pull the wheels last week (front) and re-balance. They were about 15 off. The alignment seems fine.

Still no change after the balance.

I know this is a sports car and know it's a convertible, so don't expect a super smooth ride - but I am a bit nervous to push it over 80MPH.

I am getting no noise up front - just a vibration in the wheel.

Any thoughts?

[jfoxny]

I have the same car and it's definitely not normal even at speeds greater than 80mph. If your tires are directional make sure they put them on in the right direction (there will be an arrow on the sidewall to indicate which is which). I accidentally put my tires on backwards once and got the steering wheel shimmy. :-) A bent rim has also caused the shimmy in other cars that I've owned.

Hope that helps,

Jason

Edited June 15, 2010 by jfoxny

[onlineformals]

I have the same car and it's definitely not normal even at speeds greater than 80mph. If your tires are directional make sure they put them on in the right direction (there will be an arrow on the sidewall to indicate which is which). I accidentally put my tires on backwards once and got the steering wheel shimmy. :-) A bent rim has also caused the shimmy in other cars that I've owned.

Hope that helps,

Jason

Thanks for the reply.

I did check the tires and they are the Mich. Pilot Sport. They have OUTSIDE written on the tire, so I assume they are mounted correctly.

I run 30 PSI in the front and 37 PSI in the rear. These are what the book says are correct.

Since this is my first Porsche - in general does your car track? Meaning does it seem to feel even little imperfections in the road and travel accordingly?

Again - I am only getting vibration at high speeds. If I take my hand off the wheel it doesn't steer off the the right or left, so I assume the alignment is OK.

I recall the mechanic saying the rims are not bent and they seem to look fine.

They said since it's a convertible I may experience some shimmy.

I got the tires at tirerack.com a few weeks ago.

Any other ideas?

[70Sixter]

I don't know if PS tires are directional. Are there arrows showing rotational direction? If not, try swapping fronts side to side. Stock hub-centric wheels? Spacers? Correct tighteng order of lugs? Torque?

Loosen all lugs and re-tighten to spec in proper order - opposite or star of David pattern.

You should not have this problem.

[jfoxny]

I did check the tires and they are the Mich. Pilot Sport. They have OUTSIDE written on the tire, so I assume they are mounted correctly.

The OUTSIDE marking simply indicates that that is the outside tirewall, i.e., the wall that faces outward when mounted on your rim. If the tire is "directional" then it should also have an arrow indicating the rotational direction (which is not the same as the outside sidewall). If your tires are directional then there is a distinct LEFT and a RIGHT tire and they cannot be swapped. I am running Goodyear Eagle F1 Asymmetrical tires which do not have a directional tread and therefore if I wanted I could swap the left front wheel with the right one. My Mich. Alpine winter tires are directional and therefore I cannot swap the left and right wheel. Hope that makes sense.

I would look at the outside sidewall on your tires for the directional arrow just to be sure. The arrow should be facing the front of the car on both tires. Again, I have the same car and you should not experience any shimmy even at speeds over 80 MPH. Something is wrong.

Hope you find your problem!

Jason

PS - I'm attaching a picture of my Mich. Alpin winter tires that shows the directional arrow (top of the picture). The arrow should be facing forward when the tire is mounted on the car so this is a picture of a driver side tire.

Edited June 16, 2010 by jfoxny

[stephen wilson]

What size wheels do you have? My '06 with 18" wheels does tend to "tram-line" , or pull/follow the grooves on well-worn roadways. They also transmit bumps and ride a bit rough on poor surfaces. What wheel balancer did he use? I've heard it can matter, and they should be "road-force" balanced.

Steve

[onlineformals]

Mine are 18" - Thanks for the info Steve Wilson.

I called tirerack.com and they said they could be out of round. They said to take it to a shop that has the Hunter GSP 9700 and if the tires are 15 LBS out of round they will replace them.

So I guess I am going to the dealer (they have the balance machine), as I don't trust a chain tire store to jack up my car, as I have heard horror stories about them using the skid plate as a jacking point.

Thanks to everyone for their replies.

[phillipj]

I had the same problem after putting 20's on my 997. I had the wheels re balanced and an alignment and now the car is perfect. I agree with the others... Your car should not have a "shimy" at any speed....