after these minor adjustments in tire pressure are you reaching the 120mph+ you claimed first brought this "twitchiness" to your attention? i only ask because it is very difficult to make informed decisions about such subtleties if you're merely driving around the block. but maybe road atlanta is in your backyard. that would be awesome! all i have is a half pipe lol

 

twitchiness was observed mostly at highway cruising speeds 70-100. At Road Atlanta, I backed off probably before 120mph, even though I had more power in reserve - didn't feel right at all.
Now = less steering input required at cruising speeds, lane changes - less fighting, more stable. Not perfect - but better for sure.
Aside from the tramlining, I still think I'll need to replace my coilovers at some point - at least I can wait a bit now. A bit too harsh for my daily driving.

 

I would change the tire first I bet that will solve all the remaining issues.

I have tried several tires under the sun. They are not all made the same.
Sumi's and Falkens are the most roll over side wall tire i have experienced in a 911.

 

i figured you knew enough not to be tweaking by a few psi and then making a hard and fast determination on which was best. your original numbers were pretty high though. back on point though, it;'s amazing how important tp is.

but..don't mind me, i'm just drinkin and typin sh*t lol

ps.. if i had ANY twitchiness ( tough word, that lol ) at 70MPH!? i'd freak. GL w it!

 

...then i dare say you would not be fond of hankook v12's at speed. holy crap lol

 

Pssh. Hankook V12's are crap at ANY speed LOL

Once I switched to Pirelli's my handling problems magically disappeared. Tire pressure does make a huge difference in high speed handling though. When I first got them mounted the pressure was set at about 37psi cold, when hot, they measured about 41-42. Lowering it down to 30 psi cold does wonders for handling and stability.

 

The V12's were squirming all over the place on my Supra. I absolutely hated them when they were first installed. Probably one of the worst performance tires I have driven on.

After checking the air pressure and realizing they were about 2psi lower than I normally run, I added some air and WOW what a difference.

Apparently they are super sensitive to air pressure. The must be relying a lot on the air pressure for structure. After having the correct air pressure, they were actually a pretty nice street tire.

I don't think I would ever use them on a 911, since we have to run pretty low air pressures in the front tires.

Later, Steve

 

Alignment, alignment, alignment!

There is more than one way to skin a cat.

Just because you had alignment done recently or the PO did, does not mean it is correct for what your intended uses are. Radical and aggressive settings are often done when quick turning transitions and sticking in turns under high G loads are desired at the expense of tire wear and HIGH SPEED stability.

My '04 Turbo is all stock with only the wheels replaced. It is on it's 3rd set of front and 4th set of rear tires with 25K miles on the clock. Never been aligned, doesn't need it. I don't track it but drive aggressively in the canyons and recently had it to a 167 MPH pull spanking a Camaro badly. My car felt planted and secure. I'm running without a rear wing by the way.

I use a 130 MPH hands off the wheel occasionally as a barometer for a tire, alignment and overall check. I would recommend a stock alignment as it will be best as a compromise for all things and a good starting point in getting your car sorted.

Tire pressure is important, more so in cornering than straight line performance. Your car should go straight with slightly over 30 to 50 or more tire pressure. On a fairly smooth road your shocks may be shot as far as dampening and your spring rates can be all over the place but your car should still be fine at speed. Did I mention ALIGNMENT?

I do this for a living, and have longer than most here have been alive.

 

Something to think about if you decide to change coilovers. The crux of the problem is to get the proper spring set for the turbo for the track, then you can buy shocks and have them valved for those springs. If you get something like a 2 way adjustable Moton and have it valved for the springs, you can adjust them to suit street or track. If you go PSS10's, they will be good for the street but will allow the heavy turbo to wallow on track, not good because they are too lightly sprung. I can't emphasize enough the importance of selecting the correct spring set if you will be tracking. I made this mistake and had to redo the suspension on my car in order for it to work well on track. It's cheaper to make the right selection and do it once. Moton, or other shock manufacturers, should be able to tell you what springs to get. I've heard 600F/800R to be usable for both applications, much stiffer and it will be very uncomfortable for street use.

 

Thanks Nick - I am getting my alignment specs from my shop so I can compare to the previous alignment. At least that will establish a baseline. Thanks for the info.