jford

+2 on RS specs and Mark is right about the rake. The front should be lower than the rear. I have had my car close to 140 (indicated) many times and it always inspires nothing but confidence.

Jamie

I have no ground effects other thatn what came from the factory. Although I am told I would benifit (in terms of lap times) with a wing and some sort of front splitter combo.

993inNC

For what its worth, I put the GT2 splitter on my 4S and it made a HUGE difference. The car can still get funky on bad roads b/c I run -1.5/-1.8 for camber, but as far as stable at speed I can feel the front end plant as I go faster. I can only figure it has to do with the splitter. I also have the Turbo wing out back.

David. check to make sure you tire pressures aren't over 34 (cold), suspension parts are in good shape and that the specs are set correct. My tray (tranny and rear motor) are not on and I've seen 158 before the car gets squirmy.

Ritter v4.0

Hmm. This will be a process of elimination.

Tires were 36/42 cold. Tank half full.

I wondered about the rebalancing of the car with the S front bumper with stock wing out back but would like to keep stock wing IF I can solve this problem.

The car as I said is such a rock to 110 I don't thnk its the suspension parts but I will double check.

Where can I get the RS specs? Chris- is that what you are running?

993inNC

David, I am a little more agressive than RS specs and could go more (for better track duty). here are the alignment pages from the man well.

Land Jet

My car seems more stable at 120 than 70. I got to 140 once and the car was stable, but at that speed the steering was so touchy that I felt it would be very easy to get into trouble very fast. Maybe driving that speed regularly would change my feelings about it, because I'm not used to it. I have the GT2 front and rear spoilers, and lowered to RS height.

Martin S.

some good stuff in The 911 Story on aerodynamics.

I installed the 993 RS front splitters, side skirts and tail, front and side are factory, tail is from Getty Design.

According to the 993 RS Technical booklet, the car has 0 lift on the rear at 170 mph and about 35 lbs on the front.

I have heard that the factory tail on the 993 is equivalent to a "Duck Tail". At terminal velocity, the lift on the rear may approximate what was mentioned in Frere's book, about 200 Lbs. This is all from memory, but I am close on this.

I have had my car to 140, on the track of course. It is very solid and resists side winds rather well. At California Speedway and Las Vegas Int. Speedway, you can see 135 - 140....just about run out 5th gear, sweet. This does take a toll on brakes however..pay back is a bitch.

Monty

Get your wheel balance very carefully checked. If it is out then at v high speeds it can cause a floating feel to steering. It sometimes doesn't show at the usual 60 mph. Are you on N rated ?

Bill Verburg

Unless the car is very low and stays low it will get air under it. Wings and front dams don't help unless the car is low on a well controlled suspension.

Your car should feel planted at 150 w/ no twitchiness

Don Magee

What tires? 42 psi rear may be too high. On my Bridgestone S-02As the max inflation pressure is 44psi. Other tires vary, so check that out.
Are you at the USA ride height? If so, check the rake. I lowered my car, aligned it and made sure the rake was right and the high speed stability was much improved.

ZombiePorsche44

Since I installed the new suspension it's as smooth and firm as a rock all the way to 160mph in a straight line and was really sweet in a sweeping 120mph turn (freeway transition ramp Hwy-163 S to I-805 S) even without my engine tray......lol

ZP44

Ritter v4.0

I'm RoW with new HD Bils.
Tires are Asymetricos with good tread left so I'd be reluctant to buy new ones, but will if thats the problem. I'll do the following in sequence if this makes sense:

1. lower tire pressure
2. re-alignment and wheel balance
3. replace tires
4. S wing

Miller_arch

Understood the rear should be higher than the front based on the DIY suspension tread, I believe. I could be wrong.

When I look at my car the front seems lower than the rear. I like the look so I kept it that way. But thought it might be wrong for high speed driving based on what I have read. At 110 or so it feels pretty tight to the ground.

So the front should be lower?

Ritter v4.0

Just by looking I would say that mine front is lower but will measure. Don't think that is my issue.

geolab

as said before, fine tune the front alignment.
you do not need a full alignment.
although the car has to be set up for alignment, all you need to do is
just fine pitch the tie rods to 0.02' left 002' right. total toe-in 004' L+R
It takes about half an hour to do

Flying Finn

My car at around 150 mph feels completely solid. I could drive with one hand and just be relaxed. Seriously, you shouldn't have problems you are experiencing.