I am searching for my first 996TT and went to see one yesterday. The only problem with the car seemed to be a very noticeable vibration from the front during acceleration. The car is -02 stock with about 40k miles.

It had some vibration constantly on the highway from around 50mph up, like tires being slightly off balance. The vibration could be felt through the steering wheel and the seat, but seemed to be coming from the front. More worrying was that acceleration increased the vibration significantly. The tires do need to be replaced but the wear on them seemed even.

I find it hard to believe that the tires could cause this. What could be the cause?

Thanks in advance.

 

I feel your pain, my stock wheels drove great, I bought some used aftermarket wheels which had some small dings. I realize your possible car is still stock but this might help.
I went and had them straightened at one shop and mounted/balanced at another as I also got them refinished and the mounter/balancer was much closer to my home than the straightener.
And guess what I had vibration at the higher speeds in the front. It didn't feel very Porsche like if you get my drift. So now I'm pissed right, spent all this money for cool wheels and the straightener screwed them up as how could you screw up balancing.
I take them back to the straightener and they unmounted them and check for trueness. But they check out just fine, so he remounts them in the same spot as the original guys as he marked them first and they were way out of balance. He spends two seconds on balancing them and now its perfect, smooth as silk.
Granted yours could be a different story, bad ball joints, bad rod ends, bad wheel alignment or worse cars scenario, bent frame. A proper inspection will put your mind at ease. Chances are its an unbalanced or bent rim or alignment out. Doesnt take much to knock it out of spec.
Good luck there great cars.

 

Are the front/rear tires the same diameter? There are a lot of threads on 6-Spd about the problems caused when the front/rears are miss-matched. More than likely it's just a balancing issue. Good luck!

 

I would tell the current owner/dealer to get the wheels road force balanced, then test drive again. I had this problem, believe it or not, you need the right equipment and someone who knows what they are doing.

 

Same thing happened when I was shopping for my car. The previous owner had a set of Pirelli's on the car and they were shot. I bought the car anyway and replaced the tires with Michelin PS2's and that solved the problem. I did have them road force balanced.

 

Like everyone else says, balancing could be a topic, but it's unusual to have it from all corners at the same time. What tire brand? Some softer tires, especially if car sat for a while after tires were ran hot, will be pretty bad for up to 20-30 miles before they "become round" again (of course depends on your driving style and climate). You can also heat the tires by driving a little bit more dynamic to get them back to round quicker.

These types of flat spots from soft tires will cause a "drumming" kind of vibration from all corners of the car and it does feel worse when accelerating, until the tires become hot. The hotter the tires were when you left it sitting last time, the worse they will be next time you take the car out.

For safety first though, check that the wheel bolts are all tight...
Good luck.

 

Thank you for all the replies.

Stock wheels with Pirelli tires, I didn't check the age. I am surprised if this is just normal tire balancing / replacement issue as the vibration was significantly worse during acceleration and then only slight during steady cruise.

Nevertheless that's the easiest and first thing to check.

 

My tire guy told me that Pirelli's have an internal belt shifting problem.