Son of Farquhar

Just to depart a little from the post concerning aftermarket wings and spoilers, rear end lift,etc...

At what speed does it become a little hairy for a stock bodied carrera/sc without the sport package?

I frequently see carrera's zooming by at 80-85 with no aerodynamic aids to them, and often I see a 911 without the whale tail, but with a chin spoiler (which I assume is not good).
Therefore, my question is how safe is it to drive a carrera/sc that is not epuipped with the sport package at higher speeds? Although I prefer the clean lines of the 911 without the wing, I'd like to know at what speeds does rear(and front)end lift becomes an issue.

I gather Paul Frere's book would be a good source on this-I'll have to pick it up.

Regards,
Paul

Bill Gregory

Yes, Paul Frere's book has lots of good data. In essence, around 50-60 mph is where spoilers and front valances start to have an effect. And you're correct, if you're going to have a front spoiler or valance, you need a rear spoiler or wing to provide balance. There is a distinct difference between driving a stock 911SC down the main straight at Lime Rock and driving the same car, same track, same speed with spoiler and front valance. Much more stable, stuck to the track, with spoiler/valance. I'd say it's more stable at 65-70 on the highway, too.

Son of Farquhar

...Then those people I see zooming by on I-696 at 80/85/90 mph in stock bodied carrera's are brave souls!

Bt the way, Bill, I noticed on your SC you have the RUF front valence. Pretty effective aerodynamically I assume (and looks great!).
Regards,
Paul

Steve Smith

Just a question as food for thought.

I have an '88 911 Carrera Coupe that came from the factory with the front chin spoiler as part of the optional equipment list installed on the car. The question is, would Porsche deliberately offer the Carrera with only the front spoiler, knowing the car would not handle properly without the rear spoiler installed? I think not. What's your opinion?

Just for consideration.

Bill Gregory

Steve,

That's interesting, because in anything by Porsche you read today, it says not to install one without the other. In Frere's book, he has the factory measurements of a front spoiler only installation, and it does unbalance the chassis at high speed.

Paul,

The RUF valance seems to work fine with the rear RSA-style spoiler. It's made of polyurethane, so it has some give to it. That means scraping it on the craggy roads around here doesn't shatter it like fiberglass would.

On the folks zipping by on the highway, as long as they don't have to turn the steering wheel, for whatever reason, they probably won't notice any chassis lightness. One of the benefits of the front/rear spoilers is that bursts of wind from the side, for example, don't upset things as it might against a 911 with no spoilers. It's not so much that the 911 without spoilers is dangerous at speed, it's more that with spoilers it's just safer, as it's more glued to the road.

Bill Verburg

Here are a few graphs showing the effect of the spoilers;
Front

Rear

photos courtesy of "Up~Fixen"

Jim Michaels

I've read Porsche's recommendation not to add a rear spoiler (Carrera or Turbo tail) without adding a front spoiler, but I didn't see anything about adding a front spoiler without also adding a rear spoiler. That was for '89 Carreras and earlier 911s. Porsche put a Carrera tail on the RS America without any front spoiler, but I also read where the 964 front end design provided some lift reduction compaired to earlier 911s.

Paul: It's safe to drive 911s well over 100 mph (but not recommended on public roads) without spoilers. Many have done it on race tracks for years. When I went from a no spoiler 911 to a Carrera tailed RS America, about the only change that I noticed on the track was that the car was more stable (planted) under hard braking from high speed (well over 100). Although the spoilers do have some effect at highway speeds, it's so slight that I don't think I could tell the difference. The lift reduction is probably most helpful braking from very high speeds and in high speed sweepers. More aggressive spoilers can go beyond lift reduction to provide positive down force, meaning the car is heavier at speed than at rest. And I thought it was better to *reduce* weight all this time.

Randall Lee

After taking my stock 88 cab to 100mph on the freeway, I definitely noticed "lift" at the front end. Steering was very light. I knew right away that I needed at least a front spoiler. I added the fr spoiler and the difference can be felt right away. I've seen the chart bill posted and it's convincing that even at "normal" freeway speeds both a front and rear spoiler and lowering the car will help reduce lift. I'm debating on the rear spoiler since I kind of prefer the "no wing" look. However....christmas is around the corner.....

Jeff Curtis

There are a handful of books out there that say you shouldn't do one without the other...I disagree. I wouldn't weigh my decision on installing just a rear wing/spoiler/tail on whether or not I have a front spoiler.

If it was that big of a problem, Porsche wouldn't have come out with the RS America in 1993! It's just a lightened, option delete 964 with the same front end and a Carrera tail...no front spoiler!

While it would help to add one on such a car, I run with SEVERAL guys on the track who don't have a front spoiler and seem to be stable at 130+.

I am planning on adding the RSA style spoiler to the rear of my 964, but may forgo the addition of a bow plane spoiler on the front that I want oh so badly, mostly for asthetics...but I'm sure it would provide a considerable performance improvement on the track - just can't see spending $600 on it to purchase the part, then paint it...one mindless jaunt exiting the parking lot at work would be costly!

Guys, my point is...I assume MOST of you are not using your Porsches on the track, I may be wrong. But to add a front spoiler because you have a rear, or add a rear because you have a front or not add a rear because you don't have a front or any other scenario (insert your own here) - is ridiculous if you are doing it for stability reasons in everyday driving!! A 911 is bred to go just fine WITHOUT any spoilers, on the Autobahn, at speeds of over 100MPH.

If you want asthetics that please you...go for it, you will be pleased. If you want performance out of adding wings, spoilers, lips, tails...then the upgrade is two fold.

Stephen Masraum

Going by the numbers in Paul Frere's book I can tell you that the problem with adding one spoiler without the other is a lever affect. By pressing down on one end of the car but not the other it increases the lift at the opposite end. It's supposed to actually INCREASE the lift at the rear of the car to add a front spoiler without the rear creating the potential for high speed oversteer. To those of you who don't want to spoil the lines you can always add a 964 style tail and add a switch to only put it up when you are at freeway speeds. Jack Olsen has one on his early car, it looks good.

Now from the practical side. When I bought my '88 it came with a front but no rear spoiler. I drive my car daily at speeds in the 80-100mph range and experience no problems. I feel secure in my car up to about 130. Passing 130 makes the car feel a little light. I won't do anything but a really straight line in my car at 150, and yep I've done it once (had to see what it would do ;^) ). I want to get a rear tail, but money is tight right now so it'll have to wait. This car is also at US ride height, so I really need to get it lowered too. It can't be good to have the front spoiler and also have the backend jacked up in the air like a hotrod for the US bumper laws.

Rob McConnell

Hi Paul

Just a short note, porscheworld magazine posted an article from a guy in Germany i believe who bought a 3.0 celebration, which i believe had been owned by 1 of the Porsche family could be Ferdinand not sure. Anyway the car was mint and he was scarred to drive it at autobahn speeds 100 mph+. The car had been standing for a while so it had a full service and he wrote that the technician took him out for a spin and dispelled all his worries about having no tail. I will try to find the article at home. Just something from memory to add to the debate.

Regards
Rob 91 c2 cab
Jersey, UK

BillyB

Surely the addition of a fixed rear spoiler to the RS America did not require any modification to the front chin because it was only replacing the standard, moving spoiler and the increased performance of the fixed spoiler was not deemed to necessitate an additional front spoiler.

Bill Gregory

In the design of the 964, between reseting how the windshield fits in the frame, the undercarriage panels, and other aspects, a front valance wasn't required with the 964 rear rising spoiler or the RSA fixed spoiler. It was designed that way. Previous 911's don't have the advantage of that design, so one shouldn't assume that 964 aerodynamics apply to earlier 911's.

Eric '86 Targa

The issue with the spoiler and tail is a matter of degrees. Pretty much any Porsche, as long as the wheels are bolted on tight, is more stable at 80-100MPH than just about anything on the road regardless of the size and quantity of spoilers and tails. At 100MPH+, any 'normal' configuration of spoilers and/or tails would still be more stable than most other cars on the road - and quite safe. (By not normal, I refer to some of the 'rice' style tails that probably would rip off of the car at speed)

When people talk about stability concerns with the tail and spoiler, they are refering to track use. As far as street use goes, I would bet you would feel more of a difference by changing your tires than any variation of spoilers and tails.

BTW, my car has the OEM spoiler without the chin spoiler. I've been trying to find someone to swap engine lids with me because I'd rather go tailless. I've been holding out for one that's already painted Metallic Garnet Red so I don't have to get it sprayed.

Eric '86 Targa

BTW, look closely at Bill's charts. At 150MPH the spoilers make about a 120LB difference in reducing lift. You would get exactly the same effect from putting 12 gallons of gas in the tank.