videsi

I have a 2013 A4 6MT Quattro (8000 miles) with 18" wheels and Michelin A/S tires. Tires were changed by dealer under warranty since the factory Pirellis were vibrating like crazy at highway speeds no matter how many times they were balanced. With the new tires, vibrations are better but still show up from time to time and are very annoying. There is no problem with the steering or brakes or transmission, just seat vibrations in the cabin when driving alone. Adding passengers alters the mass of the system and shifts the natural frequency enough to move out of the resonance zone (at least this is what I think is going on).

Here's a related thread I found on Audizine that talks about this issue. My post is the last one down. I have taken this to 2 dealers and they have checked everything and rebalanced tires a gazillion times, but to no avail. I would appreciate your input if you've had resonance issues like these with the stick suspension and 18" wheels/tires.

http://www.audizine.com/forum/showth...-advice-needed

videsi

stock* suspension.

snagitseven

videsi, the thread you linked to was just one of many threads a few years ago that related to 2009 and early 2010 A4 models that resulted in replacing upper control arms whose bushings were improperly designed. New arms with different bushings resolved the issue for almost all folks. (I was actually one of the people who was working with AOA on the determining the cause of the vibration).

Since the vibration is being felt in the seat, vs. the steering wheel, any issue with the front suspension is unlikely. Since you've gone through several checks for balance, etc., I'll assume you checked for a bent wheel. Even a slight out of round situation can be noticeable on the A4 - I know, I've been there. Have you tried swapping the wheels from front to back just to see if the vibration moves to the front? If no difference, that most certainly rules out tires and wheels.

So, if it's not tires and assuming not a bent wheel, it could be something in the drive train or a rear suspension component that's causing the issue. I assume the dealer has been able to replicate the vibration so I would stay on them until they come up with a solution.

videsi

thanks snagitseven. yes, they have checked for bent wheels and said everything is ok. i agree with the sensitivity of the A4 suspension to out of round tires/wheels. maybe this is why the problem is not always present and shows up when a tire has a flat spot or something. the dealer has not been able to replicate the issue since they changed all tires, but since i drive the car every day, i know it's still there. there are days when it drives smooth as butter, but then other times it starts vibrating again on the same exact road surface under same speeds and conditions. it's bizarre.

about swapping wheels, i believe they did swap them a couple of times but i didn't notice anything different in the vibration pattern. it always seems to be visible in the passenger seat-back shaking and felt through the driver seat-back. it is subtle, but over a long drive it definitely makes a difference over when there are no vibrations.

i always requested A4 to be my loaner car when i left my car for service/repair, and i noticed that one of the automatic transmission loaner A4s (13 miles on odometer) was also vibrating the same way. it had the stock suspension and factory pirellis. when i brought it up to the dealer, they said it's a pirelli tire issue. i had an S4 loaner once, and that stiffer suspension actually was better at absorbing bumps as well as reducing vibrations to cabin. this is what leads me to believe that the sport suspension is better suited for this car. i'm guessing that audi probably only tested the suspension with the automatic transmission since that's 95% of sales (guess) and didn't bother to test the manual transmission even though it significantly changes the mass of the car. also, they may have just skipped over this since the only major change from 2012 is the hydraulic to electric steering, but again that changed the mass of the car further, so if the stock suspension wasn't re-tuned for 2013, i can see why it's so bouncy. i wonder if switching to the basic 17" wheels will make a difference since the tires will then be more compliant.

the service manager has told me that he has tried everything in his power to fix this, and now he will talk to his area manager. i have told them that i will file lemon law as i'm not willing to live with this on a premium car. i will probably have to prove the issue since the dealer has not been able to replicate it, but i'm hoping my vibrations measurements (using phone accelerometers) that i've plotted on the time scale will help me out.

snagitseven

Going to a smaller wheel won't help your issue. Even if the greater rubber would dampen the vibrations, it would be just masking the problem. The sport suspension would not make a difference either IMO unless you were upgrading components and one of them was the culprit. Same for the electronic steering. I'm reasonably sure Audi goes through extensive testing on all their cars - I seriously doubt they didn't do this with any significant changes. While it's always possible something got missed or a supplier provided a defective part, there would be a whole host of threads if it was global issue like back in 2009/10 when the B8 was first introduced. There's something the dealer is missing and hopefully with Audi's participation, it will be found and resolved.

JJJJJJJ

ask them to swap four wheels from a loaner car onto your car so you can test it and rule out the wheels/ tires altogether, thus making it somewhere in the car.

videsi

good suggestion. this is what i asked as well when i took the car back in after the tire change. the problem is, they maintain that they can't replicate the issue, and they don't seem to have a spare set of wheels/tires that they can put on temporarily for me to run with and test for a couple of days. i will bring it up again when the area manager makes his recommendation.

snagitseven

If they can't or won't swap wheels and tires, at least swap your fronts for the rears and see if the vibration moves from your seat to the steering wheel. If it does, then you have a wheel/tire issue. If not, you can pretty much rule them out.

Since you've rid yourself of the Pirellis, If you feel that there could still be an issue with one of the wheels, if you haven't already, take your car to a wheel straightening specialist and have them check each wheel. Often, dealers and tire shops can miss a slightly bent wheel that a dedicated wheel straightener can discover and fix. Been there, done that more than once. Worth a try if nothing else is working.

Barrels41

MY 2009 A4 with 18" sports suspension had bent wheel vibrations felt through the steering wheel. If you only feel it through the seat it may be from a drive train mount or connection. Omission of a $.50 bushing or washer can cause much misery. Escalate with A o fA I suggest.

snagitseven

Living in the potholeville state (MA), I've had a bent rear wheel cause vibrations in the seat in all of my Audis at one time or another. Same with a rear out of round tire or a poor balance. Steering wheel vibrations would indicate an issue with something in the front of the car. As I mentioned in an earlier post in this thread, in the case of the '09 A4 and early '10, the upper control arms were designed with improper bushings that caused a steering wheel vibration at high speed (both sport or non-sport suspensions as I recall). Mine were replaced with a new version alleviating that vibration (non-Sport).