Improving high speed stability

tommy911E · 03-21-2005, 03:23 PM

My 1970 911E seems very sensative to cross-winds on the highway over 60mph making it difficult sometimes to keep it going straight and in the lane. The front end is in good shape, new turbo tierods, ball joints are good, alignment is good (my mechanic says so anyway), new tires, new Bilstein HD shocks, 15x6 Fuchs, suspension is completely stock (no bars). Is it normal for these early 911's to get blown around at high speeds? Would bars f/r help? Any other ticks? Maybe my alignment is a little off? The car tracks straight otherwise and steering is tight.

stlrj · 03-21-2005, 04:22 PM

Quote:

alignment is good (my mechanic says so anyway),

Can you consult with your mechanic to give your specific numbers?

-Joe

Tyson Schmidt · 03-21-2005, 04:27 PM

It is very normal for the early cars to get blown around. That's the reason for the front "S" spoiler bumper that camer on the '72 and '73 S, and optional on the T and E.

There is a lot of lift generated by the 911 body design, and the lift coefficient quadruples in front when there is a cross-wind. The S bumper helps tremendously. So do swaybars.

911pcars · 03-21-2005, 05:18 PM

Much as some owners prefer their cars uncluttered with fins and wings, the basic body shape does promote lift at higher speeds. The S front bumper helps the front end. However, nothing but a wing of some type helps plant the rear end so it doesn't wander.

from mild ....

.... to major downforce.

Sherwood

TerryH · TerryH's Garage

Holy Ducks in a row, Batman! Great photo! What was the occasion?

911pcars · 10:44 PM

Ducks in a row at RGruppe meet in Monterey, '04.

Vasek Polak collection at Pomona Fairgrounds/VARA race, late 90's.

Sherwood

Franklin · 03-21-2005, 05:44 PM

I put the "S" front spoiler on my 69E when I was in Germany and it really helped autobahn stability. It would get real loose over 120mph but after I had the factory put the spoiler on it was stable (so to speak) up to an indicated 150mph. Speedos in those days were rather optimistic. The claimed factory top was about 135mph if I remember correctly.

jyl · jyl's Garage

From Paul Frere's book, I gather that in cross-winds the upright front fenders block some wind from getting to the sloping front hood, thus further increasing lift at the front.

Maybe you should convert your car into a slope-nose. Ha ha.

Seriously, perhaps lowering the car, getting a slight "nose-down" attitude, and verifying correct alignment, might help a little. That is just my speculation.

I guess the real question is whether your car gets blown around by cross-winds more than it "inherently" should be. That'll be hard to tell from a written description - unless your next post is that you were blown right off the road while 18-wheelers, old VW buses, and elderly bicyclists motored along with no problem.

jeff1hughes · jeff1hughes's Garage

The early cars get blown around like crazy, specialy over 100 mph. The answer is the '72, '73 front spoiler. That alone will stablize the car a noticible amount, the duck tail just makes it that much better if you like the looks of it. By the way, nobody will slight the appearance of the early car with the '72 front spoiler, it is a very acceptable upgrade on the early cars.

tommy911E · 03-21-2005, 06:26 PM

Thanks for your help guys! I just checked my "rake" and it's set to 3/4" difference f/r (lower in front) so that is OK. Funny thing is my mechanic said the same thing about the S spoiler, that it will help a lot. Where can I get one? It looks like Pelican Parts doesn't sell it for the early cars.

jeff1hughes · jeff1hughes's Garage

I've found them in the pelican classifieds in the past, there are some after market guys out there selling fiberglass, though they don't look as good (my opinion). You can always check ebay too. One great place to go and check is at Early 911S Registry , you'll find a lot of helpful info there about your early car! That sight was a lifesaver when I had my '71 911S.

wkbergman · 03-01-2008, 11:03 AM

Same problem early on, I suspect due to the US raised bumper requirement. My '68 912 did not havae the problem with a lower bumper line.
I made an almost invisible little lip under the front of my '70 911E.
Used the angle rubber that Home Depot sells as a seal for the bottom of a garage door. Pop rivets did the trick.
Also a very slight lowering helped.