Hey guys, when im driving my car at descent speed, say 90mph it feels sort of wobbly or bobbly. Not exactly sure how to describe it, but it's like every dip or change in the road translates into the chasis and the car is diping and moving. The car dones't feel out of control or anything, just not what I'm used to typically.

My BMW 550i was solid as a rock and smooth at 90mph, it soaked up everything on the road and i could fly at 90mph and it felt like 20. Just smooth like glass.

Is that normal or do I have a potential tire/suspension/wheel issue? Is your car solid as a rock at 90mph?

 

On smooth asfalt, it should indeed be very solid. On uneven pavement, you may be experiencing some tramlining. Stock rear tires are 295s, which is pretty large. If the car is lowered, it may be even more pronounced.

All that said, I get it a little bit as well but not bad at all. Also check your tire pressure; the higher the pressure, the more pronounced tramlining will be.

 

yes. just remember the front of this car is going to feel a lot lighter than that 5 series did. more noticeable at speed

 

Still, it should be stable at only 90 mph. My suspension settings were off on my coil overs and had some pronounced instability at speeds up to 120. I tweeked that and all's well in the higher speed ranges.

So if you have stock suspension, perhaps they are worn?

 

On my 993 I had to get up to 120++ to feel any bobbing.
At 90 my 996tt feels rocks solid. Stock suspension. Uneven pavement on the back roads is another story.

 

Check your suspension and tire pressure.

With both cars in good working order they are not going to feel the same. The 550i is going to have a bit longer of a wheelbase.

 

Also check what tires you have. If you're running a mismatched set, that could be horrible for these cars. I bought my car last year and it felt great, even up to 110-120. It had H&R lowering springs on it already.

A few months later I needed to replace the rear tires and did so with some Hankook ones. After putting them on, handling SUCKED. It was downright scary. I had to take the car back to Porsche for them to dial in some extra negative camber. Changed the tires out soon after that, went back to Michelins, and it felt so much better at speed.

 

I came from BMW to Porsche recently too so had the same experience at first. Tires were the problem. They were new but were parked more than on the road. With new set of tires, now I'm scared of speeding ticket. I hit 155mph the other day and did not feel like it. I could only do 120mph on the BMW. I do feel the road more at the steering wheel on the Porsche but solid.

 

Tire pressures were off and tires are miss matched... New tires were put on the rear just before I bought it but fronts not changed at the time. Just ordered the matching tires for the front. Will report back after tires are changed on the front.

Thanks guys.

 

mismatched tires are often a contributing factor in random abs/psm cels. these cars prefer matched tires. in my experience. you're smart to remedy that.

btw. also had that 5 series bmw. there isn't really any comparison, i can think of btw the two cars.

 

That would do it. Unless you're on crappy pavement, 90mph should feel like 30mph .

 

Mine did that too...I put coilovers on and it was better...stock suspension is horrible...

 

Check these:

Wheel weights could have flown off (balance)
Alignment
Cupped tires (Pirellis do this)

 

Lots of threads on this, mine included. Came from a front engine car like most of us, and it was VERY unsettling, even at 75+. I had substantial experience, so i was perplexed at how it felt. However, took it to the track, lowered the tire pressure a bit, and prepared to scare myself. Reality is that on smooth surface it feels a BIT better, but once you get used to the odd super light front end floaty feel, it still tracks well. It's more perception than anything else. Now I'm more confident and get in more trouble

 

My car came with lowering springs and above 90 I was wagging like a dog. I put on a rear sway bar which made a significant difference, but not perfect. I then added coilovers and had an alignment and all is now perfect. I really believe the alignment was off as I went lower with the coilovers then the springs.