Flaoting at highway speeds

This is a new issue. Only has 29k. Cars seems to have become a litlle squirrely at 70-80. Feels like I have a trailor behind me in tow,kind of front doesn't seems to be connected to rear. Opinions thx.

check tire pressure first then alignment then new shocks/suspension.

If this issues just cropped up, I agree with checking pressure and alignment, but isn't this sort of a known issue with the US spec suspension? Common fixes have always included lowering the front end height from the US spec to the Euro spec, or using the aerokit to reduce front end lift.

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By 'new issue' I assume you've owned the car since new and it is stock in its suspension and aero hardware and this squirrely feel has just appeared? Then my first suggestion would be tire pressures. At 29K miles (even at zero miles given the hit or miss aspect of new car alignment) an alignment would not be out of the question. Yet another factor might be tire wear. Not sure how well this maps to the 996 but I my 02 Boxster's Michelin tires were shot. The rears were worn down in the center through the wear bars to the point lighter colored material was showing through. The car had such a downright squirreliness feel to it that I was pricing new struts/bushings/etc. But I decided to hold off until after the tires were replaced. After new Pirelli tires were installed (I had ordered Michelin tires but I found out they are currently unavailable in my car's size/etc.) the car's squirreliness feeling went away. As is my habit when 4 new tires are installed I talked about having the car aligned, but the tech told me that his experience was the center wear was not due to any alignment problem simply a characteristic of the car/tires. Save for the extremely heavy center wear the rear tires did not show any wear sign arising from misalignment issues and the fronts likewise showed no signs of any misalignment issues. The tech said further that at some point Michelin tires wear quick fast, the wear is not linear as I had thought. Oh, the rear tires had about 30K miles on them while the fronts had around 50K miles. Sincerely, Macster.

Car lowered 1",with gt3 front end. I forgot to mention that I replaced rear tires with Hankook v12,285's . front tires are in great shape but different manufacturer. Tread design very similar. Reason for change, besides being worn, wanted wider tire that older tire didn't come in 285 size. Have noticed a clunk in front end when going over payment change of say 1" difference. Made app. with dealer to investigate, and I am aware of the listed things to check. Curious I didn't find anyware that a little tread pattern would make car track differently. Anyone done this and had similar experiences? Thx.

Sorry, "pavement" changes. I also haven't been 70-80 recently until tire change.

Sounds like the mismatched tires is the cause.

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Mismatched tires always come in for suspicion. I can't offer any direct experience for I've never run mismatched tires, not even mismatched N-rated numbers, but I've read posts by some who have mixed tire types/brands and I can recall some owners were unhappy with the feeling of the car. What I have done is I have run partially worn front tires (the front tires had plenty of tread left) with new rear tires without any odd handling behavior though. Kind of drastic to replace a pair of tires just to find out in your car's case this is the cause of the symptoms/behavior but unless you can find some other reason I think you're facing a pair of tires. Sincerely, Macster.

I've had my car for 8 years and it has always felt "floaty" at highway speeds. Over the years it's had new tires and an alignment but still feels the same. I also have the GT3 front bumper. I don't have a rear wing and wonder if the aerodynamics are messed up because of the front bumper. It is stock suspension. I read about that "hunkered down" sensation some guys say their cars have and wish mine was like that but it doesn't.

Will do process of elimination, getting suspension checked out next week and probably an allignment. If that doesn't work then I guess I'm buying two tires. The old tires were near wear bars and were a little slick. I did have the feeling of hunkered down at higher speeds before. I am curious that since I went with a wider tire if that might have messed up the allignment. I will post my findings. Thx.

I think the car always floated for me, with new tires or not, the only way to get rid of it is lower the car. no need to go drastic, simple pss9 stock high will completely eliminate the floating problem, but considering Us highway speed.. I don't see the need. I prefer the everyday convenience of higher ride height.

The car is lowered 1" with eibach springs, this is a new feeling. I'm leaning toward mismatched tires. what do you guys pay for allignments, thx.

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it is very possible the presence of the GT3 front bumper and the absence of the matched rear wing has upset the car's aerodynamics. I can't call up a good mental pic of the GT3 front bumper but I just replaced the air dam of my 03 Turbo and this air dam has a distinct lip/ledge jutting out from its bottom edge that acts to generate front down force. The rear wing is of course factory (and raises at 75mph (indicated). At very high speed speed the car feels quite planted. Sincerely, Macster.

I'm wondering if the high factory recommended tire pressures can cause floaty performance at high speeds? From what several of you have said, your cars have always been floaty?? That probably means that unless everyone has worn suspensions, or alignment that's off, it's got to be something else! It's "Porsche, there is no substitute", not "Porsche - floaty at high speeds"!

When I first bought my cab. I too felt that the front end was "floaty" at higher speeds. Some research on this and other forums revealed that many were using a lowered suspension to mitigate the floatiness. I had the R0W M030 installed and indeed the floatiness was resolved. The 20mm lower front was sufficient to change the feel of the car on the highway. The ride height of the 911 sold in the US is higher than those sold in the rest of the world due to US regulations on bumper height. Porsche had to compromise their design to meet US regs. and it made a difference in how the car handled.

In addition to lowered suspension, I had to readjust my tire pressures to suit the new suspension. Never have I been in a car where a few psi made so much of a difference before

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Adjusted, how?

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I had to deviate from the factory recommended air pressure settings and experiment with different tire pressures to get a more stable handling car afterwards. For example anywhere from 38-40 rear psi was way to high for my setup and I found the rear really nervous when cornering or hitting bumps mid corner. For me there was a BIG difference setting it at 40 vs 37, even though it was only a 3 psi difference.

I remember reading about factory tire pressure for a single driver, vs. a family of 4 - with the single driver pressures WAY lower. Does lower pressure mean more stability, less squirrely behavior?

I was worried my new-to-me 40th anniversary edition with 8k had something wrong... very front end floaty at highway speed... mostly self correcting, which I attributed to massive rear tires, lots of rear end down force and a light weight front end... So loweing is really all I'm hearing will eliminate this (which I don't want to do if possible)? Maybe tire pressure changes, maybe alignment... It is an unnerving sensation really... I'd like to fix if possible

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Just try out experimenting with different tire pressures. It's cheap(or free) and easy. Also not everyone's driving style/skill/comfort are the same so find one that suits you best. If tire pressure adjustments don't work, then go after the bigger ticket items afterwards.

I saw the 997 TSB that says for HALF load (driver plus one, no heavy luggage), the recommended pressures are 33f / 36r. I'm going to try these and see if the tracking becomes more stable.

My '02 Cab feels rock solid on 18"/PS2's -- but "floaty" when I switch to my winter 17"/Blizzaks. The car should feel solid with the correct tires & alignment to that wheel/tire combination.

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Although you have made several Non-Porsche approved alterations to your Porsche I believe the tires are the main problem. Are the rear wheels 10" wide with 65mm offset? Marked on outside rim if OEM What tire size & model & brand are you running front & rear? size= ---/--/18

This is a new problem, I am running general ump 235/35/19 front, new tires are one size larger,Hankook v12's rear, 285/30/19 on a 10" rim. the tread patterns are very similar both v looking directional. One thing I have never done is run 45psi in rear before, always 34. the car tracked very well. I just lowered the rear psi to 42 and it seemed a little better,going to lower to 38. I will check back in. Also going in for suspension check Monday to correct clunk sound which I believe might be upper strut mounts, will get an alliginment while there and have them check ball joints,sway bar bushings etc.

Mine is sitting at GT3 ride height so the comparison may not be viable, but it is very stable at highway speed and above. I'm running Michelin PS2's (235/40-18, 295/30-18) with 36 lbs front and 44 rear. The only time it feels floaty is under hard acceleration in the peak torque range and all that rearward weight transfer is going on. Under more steady state conditions it feels nicely planted. I too would suggest the mismatched front and rear tires as the first variable to eliminate. Even if the tread patterns look similar there are a ton of other design and construction elements that influence how mismatched tires interact with each other.

Took mine up to 115 last weekend .. felt totally planted ... stock suspension ...i ve noticed float at lower speeds ..perhaps that's your problem driving too slow ?

Lowered psi to 38 in rear from 45 and the car felt heavy again. No twitchy feeling or disconnect. I will get dealer investigation work done and report on front clunk. Thx for all input.

Just got car out of shop for clunk sound, serv. rep told warranty co. I needed sway bar links and trailing arms. I paid for allignment. Car definetly tighter and with reduced tire psi 34/38 the wandering has stopped. Funny thing drove over the uneven pavement where it always clunks and it clunked but not as loud. He said I didn't need upper strut mounts. Go back in a few months for oil change and say it still clunks, maybe I'll get something else under warranty. Warranty bill $1k. Hope this helps someone.

using better tires help -> PS2 michelin using lower profile tire helps as well -> 19" wheels Our cars are 10 years old, all the suspension bushing are more flexible if not dead. To regain the initial stability all of those need to be updated. There are not that many afterall. My car which drove great on lower suspension PSS9 and PS2, but still he insisted for me to upgrade all my bushing and I would thank him. I did not do so and I think the car rides well, but certainly the bushing upgrade would make sense. It is just that you need to remove all part then bring them to the shop so they an press the bushing in the arms. I am surprised nobody has posted any DIY on the forum about this process. most of us use the firmer suspension and that fixes it I guess.