My 987 S slightly oscillates from one side to the other at above 75mph and appears to be doing it up to 90mph (on a track of course ). I did not get a chance to go faster yet but I suspect it is not something that goes away with more speed.

The car goes straight but I can feel a small weight transfer from left to right and then back.

Has any of you experienced this?

It appears that 75mph is when the rear spoiler extends. Could it be it? If I press the spoiler button at that speed is it going to close the spoiler?

Thanks

AW

 

Check alignment, suspension and tire pressures. Something is off IMO.

 

Could PSM be kicking in briefly when it's not supposed to? Is your bowling ball tied down in the rear?

 

> Is your bowling ball tied down in the rear?

LOL. and i hope it is not psm!

I don't see how a bad alignment could do this but I will check. I will also try to disable the rear spoiler. It is kind of subtle and not a big deal. The car handles great in mountain roads.

AW

 

AW--any update? I am curious. I have experienced this in my 993 when I had a bad shock, or when tire pressures were off by several lbs side to side. Not sure about the alignment, but I was thinking the rear toe could be an issue as was the case on 993s ??

BTW--nice radical! Wish I could buy it from ya for track days.

 

I've found the alignment being out can cause the car to feel as you describe when you go over an unever patch of road at higher speeds. Show it to your dealer, they maybe be able to work with you on getting the alignment covered under warranty.... but no gaurantees.

 

Your car has a problem and I would suspect it is a tire, wheel, or suspension issue.

I have had my car north of 125mph on the track more times than I can count and I have never felt the sensation you have described .

IMO, this problem has nothing to do with your rear spoiler activating. You will not be able to "feel" the spoiler raise. Additionally, the car will not allow you to lower the spolier at speed.

I would start by checking your alignment.

Good Luck!

 

Bad alignment, incorrect toe-in, camber and caster, incorrect air pressure can and will cause a myriad of evils in handling. Tires in themselves can make a tremendous difference. Isolate the problems at a competent suspension shop. At 75-90 your car should be rook solid; I know my wife's Boxster S is.
At 110 mph in my 997 coupe you feels as if you are doing 50 on a perfect road surface.

My old Corvette (Black Fang) is also set up to run very stable @ 80+. Brand new suspension, wheels, tires, brakes (including new vented rotors) and a good alignment fixed it. When I first got it you had to hang on to a Bible above 70 mph.

 

If this "Track" happened to be the interstate, you could chalk it up to tramlining. Not a whole lot you can do about it, and at its worst it happens from about 45mph on up.

Interstate 15 through North San Diego County into Riverside County is notorious for this.