agami

I just bought a 2008 low mileage Carrera S from a P dealer and I had him ship the car without me test driving it. There is a vibration in the steering wheel so I took it to a local dealer and he said one of the wheels' outer edge is a little bent (it's actually visible) but that it is cosmetic only and he did a balance on all 4 wheels. However, the shaking continues so I called the dealer back and he said we can try changing the wheel with the bent outer edge. He wants $850 for a new wheel and balancing !! Can a wheel with a good inside shape but bent on the outside lip cause the steering vibration ? Can this be fixed or do I need to get another wheel ?

Macster

A wheel with visible damage other than simply a scrape to its finish is always suspect.

Porsche has callouts for how much radial or axial runout a wheel can have and still be considered usable.

I would ask your local dealer if the wheel, all wheels in fact, were checked to confirm they conformed to allowable runouts.

Before you spring for a new wheel there are a couple of things you can try.

Did you have one of the techs test drive your car and advise you on what he thought the cause of the vibration might be?

Have you checked the cold tire inflation pressure? My experience is with some overinflation and not too many psi over the factory pressures these cars can develop a vibration that is has all the earmarks of a wheel imbalance but in fact is simply caused by overinflation. Overinflated front tires seem most likely to cause this vibration.

It might be worth your while to 'invest' in an alignment too. Since the car has obvious wheel damage alignment is always suspect. Again my experience is it doesn't take much of a brush against a curb, not even enough to mar the wheel in fact, to knock the alignment out, at least at corner of the car with the wheel that made contact with the curb. In my experience the car didn't vibrate after the brush with the curb though, but well, I'd consider an alignment just in case. The car is unknown to you and part of this requires you consider having various things done to get on top of the car's condition.

Lastly, perhaps you can find someone who would be willing to swap wheels/tires with your car and give you a chance to eliminate at least the wheels/tires as being at fault.

Sincerely,

Macster.

Byprodriver

Mac is right about overinflation magnifying imbalance issues.Assuming the bent part of the wheel is the source of the imbalance, if you can find a good tire balancing tech that knows how to reposition the tire on the wheel to align the low spot of the wheel with the high spot of the tire & then rebalance to optimize what you have now. Watching the rebalanced wheel/tire spin on the balancer allows you to see any up & down movement which when mounted on the front of the car transmits to the steering wheel. If the balance is still unsatisfactory you can look for a wheel repair shop that can straighten the wheel & verify the before & after results on a wheel balancer that you can either visualize or realize by the reduced weight required to balance the bare wheel without tire. If you post a great pic of the damaged area we can advise on the repairability of your wheel. It may be best to find a used wheel to replace it.

agami

Thanks for the suggestions. the tires are properly inflated (That is the first thing I adjusted). I contacted a local wheel repair shop and will post the results next week. My next option would be to do an alignment (although the dealer said the alignment will not fix the vibration).

Byprodriver

That's correct, wheel alignment aims the wheels in relation to the chassis & has nothing to do with vibrations.

CW-VIESOCK

Assuming the tire on the bent rim is not new, it may have been breached by an object large enough to compromise a belt within the tire and may have lead to the rim becoming bent in the first place. Carefully check the tire for repair. -- Yes, some tire shops will plug low-pro performance tires.-- Assuming low mileage since the event, outside tire wear may not be noticeable.
If no other wheel assembly is available to swap out, dismounting the tire and doing a lateral and vertical run-out test on the rim and inspecting the tire would be the first place to start. Before removing the wheel assembly, spin the wheel while in the air to check for a warped/dragging rotor or bad wheel bearing. A repaired tire will be easy to spot now. If not repaired, tire may have been damaged during the event that bent the rim, so the damage my not be visible at all.
If all this looks good, then bent/worn suspension components or drive-line vibration could be suspect.
I have chased these gremlins in the past and know who frustrating they can be to nail down.
Good luck.

Macster

That is not my second hand experience. In a few cases and in at least one in particular I recall on a UK Porsche board, the owner posted of experiencing vibrations from his car and nothing he tried -- including having the alignment checked -- helped.

Finally he took the car to another dealer who did an alignment and found the alignment was off -- I do not know in what way -- and afterwards the vibration was gone.

The owner was upset (to say the least) that the original dealer apparently was just blowing him off and not actually checking/setting the alignment.

In the OP's case if the car is a new car to him, unless he has paperwork that the alignment was done and he has the before and after numbers (every time I've failed to get these the alignment has been less than right...) then the alignment is suspect.

While I would not jump right into an alignment absent any other signs one is needed (but my experience is the alignment can be out and the car shows no real signs of having any alignment issues but over time tire wear will be horrific) in this case, before I went to the expense of having new tires installed, or buying a replacement wheel or wheels, or trying more expensive possible solutions, I'd have the alignment checked/set.

Sincerely,

Macster.

Byprodriver

My experience is 1st hand, unless the alignment is so far off that you can tell visually it will not cause a vibration.

Macster

Alright then, what the OP is facing is replacing the suspect wheel/tire. If he's comfortable with that then so am I.

Sincerely,

Macster.