Jay H

I apologize in advance for this long post.

Since taking delivery of my '06 997 seven weeks ago, I've been fighting a shake in the car, most noticeable in the steering wheel and in the seat of the pants.

The car was delivered with brand new 2011 18" Carrera IV rims with brand new Michelin PS2 (N4's) to replace the 19" Sport Design rims. The dealership discounted the car significantly for this swap out. When test driving, the front wheel shake was simply horrendous. The dealership re-balanced the tires and some of the shake went away. In hindsight, I should have refused the car until the issue was resolved, however, it is what it is.

I had the rims and tires rebalanced by my local dealership with Hunter road force equipment and the dealership tech said one front tire was out of round and not within spec (ride quality number of 28). The other side was high at about 20. I have been able to get a local Michelin dealership to warranty both front tires and had them replaced. The shake persists after three rebalance jobs by the tire dealership and the Porsche dealership.

This took a bit of time (at least a month) to screw around getting new Michelin tires, and with winter looming, I ordered new 18" Carrera III rims and new Pirelli Sotozerros from Wheel Enhancement. They came mounted and balanced, though the Pirellis have a date code going back to 2008. I put those rims and tires on the car hoping the shake issue would go away. The shake was still there, though slightly different. I had a local vendor rebalance that whole set on a Hunter Road Force machine, but not much improvement was noticed. One front was 18, one rear was 21, one front was 8 and the other rear had a 6 ride quality number. The lower the better. I've been told Porsche wants 18 or lower to be within spec and under 10 is ideal.

Back to the Porsche dealership. Another rebalance on the winter tires was done, but then they noticed a rear half shaft was out of spec (!?!). That was replaced. Some of the seat of the pants shake was removed from the car, but honestly, this car feels like a 15 year old Chevy with 160k on the clock, not a 20k mile '06 911.

Friday, I had yet another Porsche dealership look at the car to get another opinion. They rebalanced the winter set (I think this is the 4th time now - I've lost track of all this nonsense) and told me to try it out for awhile. I returned home with the steering wheel wobbling and the seat of the pants vibration still intact. I was told one front tire has a ride quality number of 20 and one rear is out of spec at 29 (hence the seat of the pants vibration). These numbers are worse than the local tire dealership's numbers that I got a month ago.

Wheel Enhancement is sympathetic about the condition of my winter tires, but can't do anything for me unless I ship the assemblies back to them or drive to California to have them look at the car. I'm in WI. If I ship the wheels back, I have to walk to work and deliver my kids to school on my back (the three of them would be heavy and I think it would take awhile to walk 18 miles one way, twice a day) since the summer Michelins don't work well in snow.

Has anyone else dealt with such poor ride quality numbers from tires on a Hunter machine? The 2nd dealership told me they hate Pirellis and feel they are a troublesome tire. I was told to buy Michelin snows, but those are unavailable. Could there possibly be other issues creating the steering wheel shake? Both Porsche dealers feel there is nothing else wrong with this car and I've spent about 9 hours worth of shop labor trying to diagnose this issue. All tires are the correct sizing 235/40's up front and 265/40's in the rear and all tires are N rated. All 8 rims are new and spin true.

Thanks for staying awake this long. Any ideas would be welcomed!

997_rich

Whoa.. this story sucks to hear. This should definately be solve-able with the right tech.

Have you/tech jacked the car and checked for slop in the control arms, tie rods and steering assembly? have you had the alignment checked? Ride height? If you're getting bad results from multiple wheels and tires I'd start there. I went through several sets of bushings on my front control arms on my BMW E34 which exhibited similar symptoms.

Rear half shaft was out of spec? how- visibly bent, CV joint slop? and how did they notice? was it visible? Has the car been in an accident?

First and foremost I'd make damn sure this car was in spec for alignment and that when it's on the lift nothing can knock around anywhere. Grab the wheel and all suspension members and jank them back and forth hard. There should be no knocking anywhere. Look at all bushings/ball joints and make sure there's no tearing etc. Look most closely at the front end.

Does it get worse when you brake? at specific speeds? when you're going around a right hander or left hander? All of this can help your diagnosis.

Jay H

Rich, thanks for your post. It's been a long 7 weeks... I've been working on this every week and I've about had it with this car. The P dealerships are losing patience with me and I think the Michelin tire dealership hates me since I've been back there so many times I've actually lost count. I've been super nice to all personnel at all times and the Michelin place really went to bat for me.

Here is more info to the best of my knowledge:

The car was driven home to WI at least 800 miles with the objectionable shake happening. I'm wondering if that wore something...

The car has not been hit. All the paint is original, there is no body work and even the tech said that the car didn't have a wrench mark on any of the suspension when they pulled the half shaft, so they saw no evidence of accident damage or abuse. The car had 3 stone chips, an as new interior and looked like a new car. One of my co-workers asked if it was a 2011 or 2012 model, so the car looks like it lead a good life prior to my ownership. It had a very clean DME report and passed the CPO inspection (though are those all that thorough really? I think not...).

Braking is solid, fade free and with zero pull at any level of brake effort. The brakes feel like good 911 brakes. Braking does not affect the shaking.

I can feel the shaking start around 40 mph, then steadily get worse as speed increases and at over 70 mph, it simpy drives me insane. Even my wife feels this amount of shake in the car is unacceptable in a 911. Maybe in an old Chevy... She and I are both picky car people.

I've jacked up each front and tried to feel for wheel bearing play, tie rod end slop or steering rack slop. The dang car is tight as a drum. Both dealership techs did the same and can't find any suspension issues. Both tech's spent significant time inspecting the typical suspension components that may cause such a condition.

Ride height has not been checked by any machines. Eyeballing it is all I've done and there does not seem to be any ride height issues (but again, eyeballing it almost doesn't count). The car sits very well to my eye (and I've eyed a lot of 911s over the years). But eyeballing doesn't count...

The car has not been checked that it's in alignment. However, since delivery the car used to drive like a million bucks down the road. No pull or weird feel. But, the dealership that did the half shaft replacement did not realign the car because they felt they were able to separate the suspension in such a way that it did not affect alignment settings. My experience (remember, though, I'm just an idiot) tells me that you can't do much, if any, suspension work without getting the car re-aligned. Now, the car seems to not be dead on and is lacking that Porsche 911 "feel" on the road, but I may be overly sensitive to this car's issues.

The dealership that did the half shaft replacement had the car on the rack with it running and in gear and both the service advisor and the tech visibly saw the shaft wobble or vibrate. I don't know if it was a CV join issue or if the actual shaft was out of spec. The invoice does not indicate what was wrong with the part. Keep in mind that this is the axle with the winter tire (mounted at the time) that has the crappy 29 ride quality number. After the half shaft replacement, the vibration from the rear has decreased, so it did something to replace the half shaft.

Turning left or right hard seems to help reduce the vibration, but it does not completely go away during turns.

Could I have gotten 8 bad tires? 4 bad front Michelin summers, 1 bad front Pirelli and 1 bad rear Pirelli snow?

I swapped out one new Michelin front with the worst front Pirelli snow and the vibration got worse. I have no idea if the front Michelin summers are in balance since I don't trust anyone's equipment to be in complete calibration. I have so many tape remnants on my rims that it may take me a month to get all that adhesive off the back of my rims.

This is my 6th Porsche. I have two air cooled's in the garage (that go down the road like a million bucks) and had two Boxster's prior, so I'm not a complete newbie to how a 911 and a Porsche should feel or act.

Thanks again for any thoughts...

Jay

Vancouver-BC

If possible, I would have the dealer install a set of problem-free rims/wheels. If the car still wobbles, it's not the wheels but something in the suspension or drivetrain.

Jay H

I agree. There has yet to be a baseline established for this car since I brought it home with an issue that has yet to be resolved. There are too many unanswered variables yet.

simsgw

Don't worry about the long post, it sounds like a much longer nightmare, Jay.

I opened this thread expecting to explain to a novice how much vibration you can cause in a sports car with a flat-spotted tire. Clearly, you are neither a novice nor a victim of a flat spot. We're talking about something real.

I'm not sure I've absorbed yet everything you eliminated, but let me think out loud for what that's worth. You already know a lot of this, but it may help to 'hear' an engineer thinking through what you've said.

First, the brakes. If you have worn bearings or bushings that permit play in the suspension components, applying brake will reduce the shake. I am tempted to say 'always' but in ten minutes I'll think of an exception that only applies to earthmoving equipment or something else useless. Let's just say that your description of the feel under braking rules out suspension problems, at least for a first cut. That leaves us with one of the rotating elements.

Tires. Certainly you could have gotten bad tires all these times. It just isn't very damned likely. I've never examined the figure-of-merit reported by those road-force balance machines, but it is disturbing that your tires could not be brought within the range Porsche considers acceptable. Actually, we're talking about the wheels and tires combined on that machine, but you say the wheels were tested without the tires. Furthermore, you have the same problem with OEM wheels mounted as you do with the winter combination.

One thing occurs to me that you didn't mention. I haven't checked, but I'm pretty sure that even the Hunter machine balances only the wheel/tire combination. Unlike race cars, I don't believe they ever do a full-rotating-mass spin balance. That leaves us with two more parts they haven't checked for you. Or at least you didn't mention it. The brake disks. Well, four actually, counting front and rear.

This is a used car obviously and some previous owner might have scored the disks and been to cheap too buy OEM replacements when he did the next brake job. Or... well, something else might have happened. Jeez... something had to cause this because it would never have gotten through warranty period with this problem outstanding.

Suggestion 1: Have the disks examined closely. First, see if they are OEM disks and check for mechanical damage. That's rare, but can't be overlooked. Those new 'carbon' disks can be damaged easily when a klutz is changing wheels and seriously ham-handed work could break an iron disk as well. Second, have their mounting checked. If both of those inspections report no apparent problem, then have them removed and checked for balance even if they are OEM. One of the obscure problems I remember is the vent spaces being filled by some substance that hardens afterward. I wouldn't be reaching for zebras when we hear hoofbeats, except that you've come very close to ruling out all the horses. [Old tale you can ignore if you don't recognize the reference.]

Suggestion 2: Hard to believe you wouldn't recognize this, but make sure that all six cylinders are firing. We live quite close to that lovely boxer engine and in the old days we could feel it immediately if a plug wire got knocked loose. It takes a lot more subtle problem to cause a late-model to lose one cylinder, and especially to do it without some sort of warning light appearing, but if you haven't already thought of this, it's worth checking. The heaviest rotating part in the drive train is the engine itself. (Yes, I know. That isn't a zebra, it's a bloody gnu, but I'm reaching for anything here.)

Suggestion 3: The drive shafts. This gets awkward so I put it last. To check their dynamic balance, you basically need a machine shop unless Porsche thought to include a special-purpose device in the standard set of equipment in a dealer shop. The practical way to check them is to swap them out for new-out-of-the-box units, but that isn't cheap and the car isn't under warranty.

It is under CPO however, and most of those warranties include the driveline and chassis even while excluding fripperies like air conditioning, so don't hesitate to get that coverage into the question as soon as possible. Something is bloody well wrong with a Porsche that does what you describe. You ruled out all the not-too-serious issues from your first paragraphs on. Frankly, I can't see how an alignment problem could cause what you describe with a healthy suspension, and even with bad bushings, the application of brake pressure stabilizes that sort of shaking. Even if the car is out of their warranty coverage, if those steps above... in fact, if that first step above doesn't yield an answer, then I think you need to get PCNA interested. Even granting it isn't them obligated to pay for the correction, they should help you figure out what needs to be corrected.

I'll mull this, Jay, but that's all that occurs to me offhand. I have some chores now, but I'll get back later with anything else I can think of.

Gary

Jay H

Gary,

Thank you for your response. I've read your reply in detail.

Here are more thoughts/comments:

The discs have not been removed or checked as far as I know. I will have this done. I've inspected them myself and they appear to be stock. The pads are new and the rotors don't seem to have any wear. I have a feeling that with 19k on the clock, there would be some pad wear and rotor wear. These discs and pads appear too new to be original to the car. Though, the rotors show some small rust spots in the "hat" area, so the rotors have been there for some time to to their patina. The gray paint on the rotors is correct and the proper hue (I judge concours cars for such stuff...).

I'm hoping that I would notice such a condition, but I'm not all that smart either and have little experience with 997's. The car does shake a fair amount at idle. But neither dealership has mentioned this during their inspections as an issue. I questioned this when purchasing the car...your comments regarding this concern me. The car has great power at all rev ranges and pulls like a train. Theoretically, since I never, ever exceed the speed limit, triple digits in 6th gear is (theorectically speaking) only a slight throttle squeeze away. As it should be in a 911.

One drive shaft was replaced due to one of the dealership's concept of checking the car while in gear and running while on the rack. The driver's side drive shaft was found to be out of spec.

My next dilema is where to take the car next. One dealership (I think) is done with me. They have been helpful and have done everything for free, but that free ride is over. They have stated the car is shake free and should be fine going forward. The other dealership's tech has acknowledged the shake and would like to test the car some more. The tech is slow, but thorough. Labor is sky high and parts are very expensive and at list price. I'm very used to shelling out thousands on the air cooled cars, but I typically buy the parts myself and the labor is dirt cheap at the independants as compared to the dealerships. But, that's all part of the game.

I have one more option of taking it to the race shop that does all the work on my air cooled cars. All of these repairs will be on my nickel since they are not a Porsche dealership and it's a royal pain getting the car there due to the distance and the need to rent a car for the week or so that it will take to get the car there, let them work on it and then get back there. But, so be it...

Thanks again to Gary and Rich.

okbarnett

for anybody else with a problem like this, try to get the dealer to swap a good, or new set of wheels to check the problem. they should be more that willing since they have not determined anything on their own.
also the operator of a good road force balance machine should be capable of reading the results of the machine, well enough to narrow this particular situation down alot more that having to go back and do the job a second and third time. i think i am blameing the operator now for any further questions about the tire/wheel validity

McCulla

Please excuse this addition as I know NOTHING about this particular item, but have heard this mentioned with vibration...motor mount?

simsgw

That is worth checking, Jay. Especially because you say "The car does shake a fair amount at idle." I could not honestly say my car shakes at all when idling, let alone a fair amount. Admittedly, we have a different engine in the dot twos, but neither one is a configuration that shakes. The flat six engine layout is inherently balanced. You can feel one of our engines running, but you never should feel it shaking.

Another phrase keeps coming back to me:
Why? And I mean that twice: why was the car discounted for the wheel change and why was it deemed necessary in the first place?

Many of us install the 18" wheels because they have advantages in track work, but nobody ever offered me money back for my nineteens. And I'd certainly have no reason to do the change when I planned to sell the car -- unless I needed to replace the nineteens and wanted to save some money. What that sounds like is severe curbing led the previous owner to sell it, and I don't mean 'curbing' as in misjudgment when parking. In this context, I mean a loss of control that led to the car sliding into a curb, presumably with both wheels on one side damaged.

I may be reading too much into that paragraph of yours. Can you tell us more about the situation? If the car has been slid into a curb, I can see getting away with no visible body damage, but with damaged suspension members and possibly bent mounting points where the frame picks up the moving suspension elements.

Gary

WCE

I agree with getting to the bottom of what necessitated the wheel change in the first place. The half shaft mysteriously found to be "out of spec" doesn't sound right either!
These cars transmit any rotational imbalances directly to the driver - it's all part of their charm but also a challenge to keep everything nearly perfect. My 996TT would shake and bounce from simply being parked in the cold for a few hours unless driven until the tires would warm up a bit and become perfectly round again!

simsgw

Hmm, yes. Mine does that too, and we don't even live in a very cold climate. So far, the Michelin PSS tires seem less given to that behavior than the PS2's were.

Gary

997_rich

Agree with trying another known set of good wheels and tires- any friends with a set? It would be nice to rule out wheels and tires.

I'm almost ready to say that it's not the tires and wheels after two sets but you should try with a known good set. One time I got 3 bad thermostats in a row from different dealers so lightning can strike twice.

Do you have a dial with a magnet arm? or do you know someone with one? Maybe you can jack the car and check the run out on the rim surfaces with the dial. You can try to do this with the tire on the rim or just bolt up an old good rim and dial it. You can also dial the rotors for run-out. you can also dial your half shafts at the center. Run out of much more than 0.5mm on any of these parts can really point to an issue (it should really be less). This might be a cheaper approach (buy a dial and magnet arm for $50) before taking it in to your indie shop.

Does the steering wheel shake side to side? Look first for axial (side to side) run out. steering wheel shakes but doesn't rotate? Look first for radial run out.

here's a pic of the control arm on your car (or similar ones). look very closely at the rubber bushings at the end. If the car has hit a curb these can get trashed and cause the symptoms you're explaining. Sometimes you can't even see the crack until you pull the part but the bushing is trashed. http://www.suncoastparts.com/product...ry_Code=997sus

Gary makes a good point about hitting a curb... at this point I'd guess this car hit a curb or it had aftermarket suspension and the settings are wierd.

I'd insist on an alignment (esp. toe) even if you have to pay for it. If a car has 0 degrees toe you can see these kind of symptoms. It only takes a few minutes with the right tools. This is difficult to do at home.

My experience with vehicles that I've worked on is that 90% of the time when you get a ride shake it's coming from the front end so I'd focus my efforts there.

Good luck and please let us know if it gets sorted.

Jay H

First off, thanks to everyone for their comments. This discussion is very helpful. After fighting with this car for 8 weeks now, I'm somewhat frustrated.

I'll try to answer everyone's questions:

I paid close attention to this tonight on the way home from work. There is a significant amount of shake in the car at idle. It'll make the driver's seat shake for sure. I've never had another car shake like this at idle. My 987 Boxster never exhibited such behavior.

The car was originally equipped with 19's. I received close up pics of the 19" rims and tires before purchase. One rim had a small scratch in it, the rest were flawless. The 19" Continentals were not original tires and had about 6-7/32nds of tread depth on them. During the 10 days of negotiations I went through, they sold a new 2011 997 and removed the 18's from that car to replace them with some custom wheels the customer wanted installed. So, the 18's were "laying around" and the dealership offered that set of rims and tires to me. Since my car was no longer carrying all it's original equipment, they offered to reduce the price of the car a bit more for the downgrade. It was my choice to accept the car with the original 19's or the new 18's for slightly less.

I asked the dealership that did the half shaft swap if they saw any accident damage. They found nothing suspicious and they warned me that they would not honor the CPO warranty if they found any modifications or accident damage.

Agreed. I call BS on the half shaft being out of spec too. That just doesn't add up. I was skeptical on that repair. I also know that the rear tire that is on the axle that the half shaft is located is giving a 29 pound road force reading which is way beyond what Porsche calls for as a maximum (18) and way over what Hunter balancing equipment says is the max allowable for a proper balance (22). That tire has gotten worse over time (originally spec'd with a road force reading of 21 back in early October when I had the winter tires re-balanced the 2nd time). Could that way out of round rear tire fool the tech into thinking the half shaft was out of balance as the car was run on the rack in free air?

I also agree on this point. I've only met one person in my lifetime that could properly balance a set of tires on the first try. He owned his own 1 man shop and had brand new Hunter equipment and, most importantly, knew how to operate it and what all the settings did. I was able to spend quite a few Sat. mornings having tires mounted by him over the years and learned a boat load about how to balance a tire. There is an art to it. This man retired and moved to the west coast, so I'm out of luck getting his help on his machines. People used to come from 200 miles away to have Ron do their tires. He was that good.

I really would like to swap out rims and tires from a "good" car. The one dealer may do this, but they feel the next step is to replace the two winter tires with high road force numbers with new Pirelli winter tires and see what happens. Well, first I was told to "just live with it, it's not that bad". Well, if I wanted to "live with" shaking while I drive, I would have saved myself $48k and just bought a 18 year old Chevy.

I do not have that equipment, but it's a good suggestion. I've watched several of the rims spin on various balancers and they spin true. The one tire shop checked all the rims while balancing the winter tires and felt everything was perfect. The rims were from Wheel Enhancement and marketed to me as new. They were delivered in flawless condition.

The wheel does shake side to side. It's the typical shake when you have an out of balance front tire. A very common shake to me since I've experienced this in most cars I've owned until I would replace tires and/or have them rebalanced by a competant tech.

I agree. A full alignment must be done on this car. Too much goofing around has been done on it (especially with the half shaft replacement) to know for sure if the alignment settings are still intact.

I feel that there are several issues at play here with this car. The one rear tire at 29 pounds of road force is definitely playing havoc. The half shaft replacement repair seems suspicious in suggesting the tech missed diagnosed that. The shaking at idle is making me nervous as well...

Again, a huge thank you to all that have responded to this thread. Thanks for letting my type all this crap out too. It's almost like therapy to discuss the issues since the car has been nothing but issues since day one. I'm still wondering if the selling dealership (a large, well known dealership) knew about this car...

Best to all,

Jay

hoffa

Jay, you are not alone. I have had the same issue with my car. I have convinced (maybe incorrectly) that this is a potentially bent rim or flatspotting on the tires. It is much worse with my winter tires/wheel than my summer set. With my winters, its noticeable between 80-120 kph, with my summers its mostly 100-120. Sometimes it "gets better" after the tires warm up, but never entirely. The steering wheel rotates back and forth a few degrees, if you barely hold it. It does not change under braking. FWIW i also have a vibration when idle - not sure if its normal - but when the car is still and idling, the passenger sports seat vibrates. I just figure this is normal.

I have had numerous tire balance and alignments (dealer & not dealer) but the issues comes back. I have somewhat given up - just deal with it in the winter, and in the summer its subtle.

On the track, it pulls really well (compared to peers in my run group) so I didn't think it was the engine.

If you do make progress I am very interested to hear.