Jan_M

I had my car recently alligned to factory specs, new PS1 tires. On dry the car is glued on the tarmac as it should be. When the road is wet, it starts to somehow "wobble" a little, as if it was porrly alligned!

Does your do that too? What could be the reason fro that?

LVDell

Does it wobble on dry? Does this happen only when you are braking or just cruising? The PS1 isn't really a good wet tire as it is dry. You sacrifice proportionaly wet or dry handling when you err to the other side.

Jan_M

LVDell: Dry grip is fantastic. It is happening when I am cruising on the highway at regular speeds (90-140 km/h). The PS1 only have something like 3-4000 kms on them.

LVDell

Have you had them re-balanced? Do you have spacers?

Jan_M

No spacers. Wheels are balanced.

LVDell

Sounds like the Cayenne wobble at cruising speed. Many have suggested that it can be as serious as having to replace the driveshaft and as minor as just getting the wheels rebalanced.

One other thing, you could have very well got a bad set of rubber. But my guess is on the balance issue.

Aside from that, I am out of diagnoses.

LVDell

One other thing. Do you have another set of wheels/tires for the car? Like a track set or winter set, etc.? If so, run them and see if the vibration is still there. I am beginning to think you have a bad set of tires. They could be not true (round) or have a flat spot which would lead to this.

Bob Rouleau

Please describe the "wobble". A 911 will be less stable on any road when there is standing water. If there is a lot of standing water and speed is high enough it will aquaplane very easily.

Rgds,

earlyapex

This sounds like hydroplaning as the problem does not exist on dry pavement and you describe your car as essentially stock.

Jan_M

It certainly feels like some sort of hydroplanning as the wheels seems to be "sucked" in the wetter spots and the car becomes much more sensitive to laminated tracks on the road. I'd be OK with that phenomenon at higher speeds, but am reluctant for that on a 996 at around 130 Km/h.... Isn't that a rather low speed to get those behaviours?

1AS

As dumb as this sounds, I would be inclined to go to another dealer and recheck the allignment. Before that,
I would pull every tire off the car, put it in a balancer and make sure it is round and make sure you don't have a bent rim. Also, look to be sure that the weights are distributed evenly around the circumference and you don't have excessive weights applied for balancing. 2 smaller weights 60degrees apart is better than one large weight centered.
Then, I would retorque them (I mean personally) so that no jerk did it with an impact wrench.
I'm sure you have already checked pressures carefully.

I have been around long enough to see many mistakes due to lazy or inexperienced workers. I once took my then-new SC from the dealership after new rears, and found the instability to be due to 90psi in one rear tire. One new set of tires had a tire that required a huge abount of weight in one area which caused it to feel out-of-round. Ones set of Pirellis suffered belt shift.
If everything checks out, i suspect the most likely answer will be one bad tire. Let us know. AS

Jan_M

I have had bent rims on my 993. It does not feel like this. The wheels are balanced by a proper mechanic. Pressures I have checked and gone back to OEM Porsche settings, just to make sure.

Could be wrong torquing of the nuts, and somehow it shows more on wet roads. Good hint. Will check it out and get back.

Or let me put it this way. I know 911's favorite surface is not wet roads. At what speeds on wet do you guys start to feel rather "uncomfortable"?

LVDell

Maybe others can chime in on the wet road condition, but I don't drive on wet roads. We rarely get rain here in Las Vegas and when we do we know in advance so I stay away. Last time I tried to drive in the rain here I lost control of the car at <20mph!!!

bavarian

This may be s stupid question, but you mentioned "new" tires. The first 50-100 miles are notoriously slippery because tires come out of the mold with a residue which takes some time to come off. Wet road surfaces will definitely exacerbate the problem....

1999Porsche911

Sounds just like the symptoms of worn back tires. You do not mention whether it is loose in the front or the back. As a properly aligned 996 has a negative camber in the back, the inside of the tires will wear down to the belt while the outside half still looks good. You do not notice any handling problems on dry roads, but as soon as you hit wet ones, the back end will feel like you are on ice. But since you say you have new tires, I would check the camber setting.