Good morning.

My 991S is behaving strangely, though it's hard to explain....

Do you know the feeling when you drive over uneven pavement (e.g. grooved pavement), and the car kind of swerve slightly?

For the past two weeks (strangely after an oil change at the Porsche dealer) it's been behaving like that...

I thought it was because I had extra high tire pressure (45 in the back!), but even now that I lowered it, it's still doing it.


Any ideas?

 

Doesn't have to be grooved pavement but pavement where, in my case, the level of pavement is different and curved between the tires (front to back). Feels like a grab-slide along a diagonal axis. There is a curve like this on my daily drive and I get this effect every time. Just normal behavior me thinks.

 

I thought so, but at the same time, I kind of noticed it only over the past three weeks....Do you think if I air down the tires to 36 in the back, it will be less noticeable?

 

Alignment could be off. Maybe they rubbed a tire when it was at the dealer and it screwed up the alignment of one of the wheels.

 

Thank you! I'm going to get it checked.

I can't believe it's always been this way and I haven't noticed. I was always perfectly balanced and now it feels like it went through an accident...weird

 

I get it whether the TP is high or low (comfort partial or regular).

 

Sounds like a combination of alignment and tire pressure. Try to get the dealer to fill nitrogen and maybe set pressure to comfort.

 

What's the difference with nitrogen? Actually, never mind, I'll google it. Im sooo lazy! Thank you!

 

Nitrogen makes up most of air. Being a larger molecule than oxygen, it leaks out at a slower rate than oxygen. These molecules actually wend their way through the tire's molecules to escape. Not sure how having a nitrogen fill would affect comfort level, however.

 

Over here the tires always get filled with nitrogen nowadays. I don't think I've driven a car without it in the last 5 years. I was told that it also expands or contracts less when a tyre warms up or cools down. I'm not a chemist, so I have to trust on what people tell me

 

check to see if a wheel balance weight fell off?

 

That can also be the cause. Thank you!

 

Actually Nitrogen is preferred due to the fact that it is dry compared with air and especially gas station air pumps which have no driers to remove moisture from the air they dispense. A Nitrogen fill reacts way less to temperature deviation which leads to increased or decreased tire pressures depending on ambient temp outside and how hard you are working the tires (say on a track).

 

oooooh nooooooo, not this one again.....

 

I just mentioned nitrogen because it may lead to lesser fluctuations caused by temperature. Just so that we don't deviate from the op, just fill the darn things with camel farts if you prefer! Heck what do I know.