How stable are you at 100-110

[Siena911]

This is not a race story!!!

This morning, on a stretch of motorway, there were about three cars?? Anyway a badass Bentley was just itching to get past, so I moved over for him and let him go.... But once the rabbit's bolted the greyhounds just gotta chase

So we got up to around 105, he was still about 150 yards in front of me and kept a constant speed.

I noticed that it felt like my car was being slightly buffetted by wind, but there was none in the trees etc. It was kinda like I had to hold the steering more tightly to keep it going straight (does this make sense)

Is this due to road surface not being too flat, or just the speed or is it my suspension geometry thats slightly off? I've never driven another Porsche at speed so I've got nothing to compare against.

Cheers Jakes

p.s. What really amazed me is that it just kept wanting to go

[AirCooledExcellence]

Hi Jakes,

I've noticed the same effect on mine, and think it's due to variations in the road surface. On a good quality stretch of road I've had mine up to 120, and solid as a rock.

If you haven't had one done lately it probably wouldn't hurt to get an alignment.

Cheers,

Tim.
____________
1983 SC Targa

[fastbydrmike]

That same thing happened to me only with a corvette C5. I pushed my car to 140 and it was rock solid. I was impressed!! It didn't do anything weird.

Mike

[k9handler]

Yesterday I made a run on the local Autobahn, just as I entered the unrestricted zone I ran her up to 130 mph for about 10 miles...this was easy to sustain and felt very stable.

[beepbeep]

It's pretty common, especially if you take out reserve-wheel from front compartment.

Also, lot's of camber will make it feel twitchy...mine feels same.

[RoninLB]

with no front spoiler or rear tail anything above 90 for long stretches in desert or Colorado's I-70 is a PIA/to much work. I think that without downward help the 911 gets PIA air under it.. wind guests over 20mph does affect/complicates things.. and my 911 is tight, w/S-03s, big street springs, and Welt bush........Ron

[dickster]

i agree with other comments.

are you running front/rear spoilers?

i was running just the rear at first and found a similar sensation. now i run a lip spoiler as well and its now very stable at all speeds. just goes where i point it.

i've experienced (as a pasenger) 145mph in a turbo escort, seria (sp?) cosworth, and an '82 sc - and the 911 was by far the most solid and enjoyable ride. the other two were very twitchy and pretty scary.

[5axis]

I can report that my turbo cab was quite stable beyond a indicated 140 with the top down. The noise level was up there though. Perhaps stability is somewhat relative. I had lots of miles at very high speeds on GSXR 1100. I think I felt more comfortable at those speeds on two wheels. This I attribute to having a closer relationship with the bike.

david 89 turbo cab

[Deeks]

So Dickster.... there's a 'Cossie Boy' inside you wanting to come out...?

[dickster]

oi deeks no!!

that was over 10 years ago, and you got to admit they were pretty good value at the time?? the saphire was pretty good looking. what else could do 150 for the price??

......i have to admit to having owned a capri or two..........

.....but those days are long gone, i didn't know better, and i had no money, i had long blonde (bleached) hair, lived in a caravan, and smoked pot.......

[Jocke]

Originally posted by dickster
i agree with other comments.

are you running front/rear spoilers?

i was running just the rear at first and found a similar sensation. now i run a lip spoiler as well and its now very stable at all speeds. just goes where i point it.

i've experienced (as a pasenger) 145mph in a turbo escort, seria (sp?) cosworth, and an '82 sc - and the 911 was by far the most solid and enjoyable ride. the other two were very twitchy and pretty scary.

Same with my 930 it was unstable in that speed with the original Bumper, after getting a lip it´s exellent!!!

/J

[MrKJBlue]

Have factory spoiler on front none on rear and feels stable 100 to 130 on the straight sections. can feel a bit "floaty" on sweeping sections of motorway though.

[A Quiet Boom]

I've got a front spoiler and rear ducktail and the car is very stable beyond 100, I tend to get a little loose between 50-70 when theres crosswinds but if I punch it up to 80+ either the spoliers are working better or the forward thrust of the car offsets the wind better. Don't know how this will affect cornering ability but on my drag-cars I always run maximum caster to keep them straight at 130+ going through the traps, so I had my alignment checked when I got new tires and found the PO had an extra degree of caster as well as more camber front and rear than stock. I liked the way the car drove so I left it that way.

[stormcrow]

I noticed on my 78 SC Targa that it seems a little light on the front end when the gas tank is half full or there are no tools in the front to add a little more weight.

With a full tank of gas - no problems at 130. Not sure why since I just had the front end aligned not too long ago. But it seems it has always been like this.

It does have a little nose down in the front and I was thinking that maybe with the rear a little higher it could be causing the problem when. Havn't done anything with it since I always keep the tank full or about 50 lbs of tools in the front.

Steve

"A Porsche does more then just go fast in a straight line"

[tobluforu]

My car feels like crap over 100mph. I have gobs of negative camber, 1\16th total toe out, lowered 3" or more. Bad bump steer at anything over 70 mph. Front and rear spoilers. I can feel the car being pushed down at over 75. But, my car handles excellent on windy roads up to about 70mph. Since I don't really drive it that much, especially at high speeds, I went the other route.

[tryan]

like an airplane wing ready for lift off in triple digits.

no tail . no spoiler. twitchyness goes away with the front boot filled with pano's.

the 60 to 90 rush keeps me happy. i save the high(er) speed stuff for safer/newer rides.

[Superman]

I have zero toe and some negative camber, and this is not the right setup. Especially the toe. Toblu, your instability problems are likely cause by the toe more than anything else. Next time mine is on a rack, it will come down with a little toe-in. Road forces act to push the leading edges of the front tires away from each other. That is, road forces increase your toe OUT, as you drive. The higher the speed, the more the effect. So, in order to have front end parallelism during driving, there needs to be just a little toe in to compensate.

If your front end is toed out during driving (like mine is and like Toblu's is), and if you also are running a bit of negative camber, then you will struggle to keep it going straight. You'll struggle and loose. It will 'swim.'

[RoninLB]

the 0 toe is w/wheels pressed , otherwise set for slight neg to get 0 w/rolling..some autoX guys go for toe out to make the car jumpy.......Ron

[Ove]

Siena911,
There are a lot of things that can make your car feel unstable at high speed. First thing to do is to get an alignment and check the shocks. Keep the fuel level above half. If it's lowered get a bump steer kit. If you don't have front and rear spoilers you probably don't want to get them unless you often go above 90mph, but remember to get both front and rear or none (or stay below 90mph).

I've driven my 911 at speeds between 90 and 130mph for an hour or more on a couple of trips this summer. It feels stable, even though the wheel alignment is way off. My car is a widebody with front and (early) rear turbospoiler. 225/50-15 in front, 285/40-15 rear. Lowered, but no bump steer kit (yet).

The wide rear tires and wider rear track make it a little nervous at lower speeds depending on the road surface, but this seems to go away as the speed increases.
I think the spoilers help a lot in increasing downforce. Lowering the car makes less air go under it, thereby reducing lift.
Always use front AND rear spoiler (or no spoiler at all), never just one of them!!! Using only one spoiler will change the handling caracteristics dramatically at high speed which of course can get you into a LOT of trouble.

[Bill Douglas]

I've got a little tow in, fairly low ride hight (lower than euro), corner balanced, front spoiler - no rear, and the faster I go the more stable it feels.

The only time it went a bit whacky was when I came over the crest of a small rise at 120mph and it was a little floaty for 30 seconds then became rock solid again.

Bill '79SC Euro.