Still having tire problems
 

I posted here a few weeks ago about a continuing problem I am having with new tires. Back in August I put a new set of Hankook V12's on my box. I had them balanced 3 times and still had vibration in the steering wheel. The last time I had them balanced it was a road force balance. I purchased the tires from Discount Tire on line. I got some advice by a local race mechanic that puts tires on all kinds of race cars including Porsche. He recommended that I get an all season tire because they would not get flat spots from sitting and would run out just fine on my car. With his recommendation I traded my Hancook V12's for Yokahama ADVAN S 4'S. Very nice Ultra High perfromance all season tire.

So, here is the issue. I had the new tires mounted and installed by a discount tire local install center. They were road force balance with me watching. All well within specs. Also checked the alignment and it too was within specs. Rims were very straight. The tires still vibrate, shaking the steering wheel. It happens every morning when I leave for work and is very pronounced at 35 to 40 mph. There is no noticible shake or vibration at 25 to 30 mph. It continues to get worse as I gain speed until the tires warm up and then they only vibrate over 70 mph. If I let the car set for a few minutes or an hour it runs out pretty well until I get to over 70 mph but the vibration is till there at 60 mph but almost gone. No shake at 35 to 40 once warmed up. It only happens when it sets overnight. It is in an unheated garage on a cement floor.

Questions are, does anyone have any idea if anything mechanical would cause this condition. My local mechanic want to look at the rear axle. He say's it could cause a vibration similar to a tire balance problem if it was going bad. I think it could be a motor mount. Temperature does not seem to be a factor because I had the same problem in August as I have now in December. Any other ideas what could cause this issue? If I run the car up to 80 mph it does seem to get worse and would not want to drive there for any length of time. Another thing I have noticed is that when I let off the gas at 80 mph and just let the car slow down, the vibration is much less noticable when it gets to 65 or 70 mph. When I give it gas and get back up to 70 or 75 it comes back again.

It is not fun driving my Box under these conditions. Any help would be appreciated.

By the way I have a 2000 base with 55,000 miles.

:confused:

Are you using the oem wheels ?

The soft tread compound of a Ultra highperformance tire is the main facter of cold weather flat spotting so I don't know if you made much progress with the tire change. The tread design is the main factor of a all-season tire & more cuts in the tread design= more noise & potential for ride disturbance especiall if they wear unevenly. If your wheel & tire have more than 2oz of weight for balancing you have yet to acheive optimum balance. Your easiest 1 step solution is to take your car to someone that does tire balancing with the tires mounted on the car

Had the same issue with my Infiniti FX35 when I replaced good years with Yokos. It developed a flat spot when sitting overnight or over the weekend. Symptoms were exactly what you described. Had many wheel balancing and alignments done. Dealer checked the tie rods etc. Ran it for few k miles and broke the tie rod. Long story short It messed up the car so much I bought new set of good years. But, the damage was already done. Ended selling the car and tire are still in my garage.

Call the seller/manufacturer and trace the batch. Maybe faulty batch. I was also told that it could be that the tires are not rated for low temp and that causes them to develop temporary flat spot. I'd hear a muffled thump-thmup which went away when warmed up. But, gave my steering a good shake.

By process of elimination, it was not the tires. "A morning vibration" very difficult to diagnose over the net. Get your car in to a qualified local Porsche mechanic and have him drive the car 1st thing am to replicate the symptoms. An experienced shop will make your car right in no time.

This might sound silly but to eliminate tire flat spotting as the possible issue put the car on jacks overnight (say a Friday night) drop it sat morning and take it for a drive.

Johnny,

Yes they are stock wheels, 18's.

You've tried several tires, had them properly balanced and still have the problem. It's not your tires. Don't worry about "flat spots". I've driven 4 Porsches over the years with 2 being Boxsters and I've NEVER had a problem like you describe and I work out of town 3-4 weeks at a time. I get home, remove the dust from the car, drive off and everything's perfect.

Like stated above you need to take your car to someone who can diagnose this in person, not on the forum. You've got an issue - not tire related. You have a problem that resolves its symptoms when it warms up. So leave it somewhere overnight - with a qualified indie or dealer mechanic and see where it goes. Good luck.

I wonder if it could be a bad shock issue. Is there someone with a know good set of wheels you swap on?

Yes drive shafts can give you a issue similar to wheel balance but because your shafts are in the rear I don't see it affecting the steering wheel.

drive shafts tend to vibrate during acceleration and tend to go away when speed is maintained

I feel your pain. I am going through almost the exact issue, thought I cannot actually tell if the vibration is coming form the front of the rear. Tires have been balance three times, No obvious mechanical faults have been found, axels, a-arms, wheel hubs… motor and trans mounts were replaced last year. I put the car up on jack stands today to look it over myself nothing looks out of sorts. I did notice some oil like substance in the front right wheel area that could be from the per steering rack, beginning to wonder if the per steering rack cold cause a vibration…

The slow speed vibration does seem to manifest itself from the rear of the car. Especially drivers side rear. My indi is going to try and see if he can find a set of wheels and tires to try on the car to eiliminate the tires all together, or prove it IS a tire issue. He will also check everything over at that time and see if there is anything else causing the issue. It is very annoying.

You have said that the tires have been rebalanced several times? Were they wrong the second time, third time?

I had a truck that had a bad tire- it would shift weight/ balance. The shop could balance tire and I would drive it 10 miles or so and vibration would start go back in and tire would be off at least a 1/2 ounce. They swapped tire out and fixed problem.

Have your wheels checked with out taking of wieghts to see if they have changed.

Actually I believe the problem started when he put hankook tires on his car & nothing else was changed. If that is correct I can troubleshoot his car via this forum.

What are your cold tire pressures?

We are assuming he is giving us all the pertinent info, this is not always the case with all people on all posts.


I cannot count how many times I've diagnose problems with false or missing info over the phone or email, because the tech did not think it was pertinent to the problem.

His original post was detailed enough for such a simple issue but I believe he is listening too much to otherwise qualified mechanics. When I was in charge of maintenance for PCNA's press fleet cars I had to school the service advisor at the local Porsce dealership. Way to many old-wives-tales still alive about tires.

If you want to rule out a warped wheel, bring you front two tires/rims to a Wheel America shop or other quality wheel repair place and ask them to tell you if the wheels are spinning true. This may cost you some money, but it sure will help you know what is not the problem.

BTW, Discount tire and most mechanic shops cannot or will not do runout tests on wheels for you, and if asked Discount Tire will tell you they didn't see any warping visually (which may be true, but isn't what you need. You need a proper measurement taken on the wheel rim, inside and out, to see if it's oh-so-slightly warped). Even a slightly warped wheel on our cars will cause vibration.

The reason I know all this is that I fought wheel balancing for a bunch of years on my car until I bought new rims and discovered that I had wasted many hours and dollars attempting to rebalance tires and wheels that were warped.

Tire pressures are 29 front and 34 back. I did not have this vibration issue with the tires that came on the car when I purchased it in May this year. They ran out very smooth. They were Michelin Pilot Sports. They were just completly worn out on the inside back tires and needed to be replaced. I don't know what other information I can give you at this point that I didn't give in my first post. My true thoughtls are it is mechanical because it is the exact same vibration I got with both set of tires I installed. NO improvement or not a lot worse either. I am told it is not the wheels because they were done on a new road force balancer and it would pick up any wobble or high spots and allert you. The only thing that still haunts me is the coincidence that it started when I changed tires. Of course this all happens when the snow is about to fly in Kentucky and I was going to put the box up for the rest of the winter. Would like to get it taken care of before letting it set.

Problems continue.
My INDY put on a set of bridgestone potenza's (times and tires) on my car and i took it for a test drive. It ran out very smooth. So, I went out today at a very reputable tire store and had them put on a set of Michelin Pilot sports. Took the car for a test drive and the shake again starts at about 69 mph and continues as speed is gained. At about 80 mph you can feel the whole car shake. At 73 mph it is only noticeable in the steering wheel. The manager from the tire store when with me and witnessed the issue. They rebalanced the tires again and possibly made it even worse. My INDY checked the tie rods and everything seems to be very tight. The tire store said that they can not see any wobble in the rims or that would be the obvious problem. I had no vibration in the front before I started this whole ordeal back in August. I am at a loss for solutions. I just thought I would look to anybody here that may have had similar problems before I take it to the stealership and have them diagnose it.

Thanks for any help anyone could give at this point.

P.S. My INDY says that this is the only time he has run into this. Of course it only happens to me.

FT

What you describe is just what I currently have and issue with. Mine is at the same speeds too. I would love a solution to this. I have also been told to change my motor mount and that this would help. Have you done this? Lets see if we can solve this together. Mine starts at exactly 68 and gets worse the faster I go. Happy New Year!