got my spoiler retorfited... impression

got my spoiler retorfited... impression

so i ordered my car without the carbon fiber spoiler because everyone said it didn't do anything to improve performance... two days after i took delivery, tesla increased their pricing by breaking out all the options... then i saw the spoiler description of 77% less lift...

i ask if i can get it for free as i was looking for the best performance. after some back and forth, got it for free. the mention it was a back ordered part and will not be able to give to me until probably 6 months later. luckily i found one at the service center and they installed it for free and i got the spoiler for free as if i had ordered it originally! thanks tesla!

well i can say it definitely makes the car feel more planted at high speeds! even though i had the upgraded suspension of the p85+, at high speeds above 80mph it would feel like it was floating around, definitely didn't feel planted like at low speeds. with the spoiler it makes a world of a difference!

it also doesn't look bad on my white car like it originally thought. worked out great! love the car even more now!

Thomas N. | September 11, 2013

Very surprised that you could notice the difference.

Bighorn | September 11, 2013

@Thomas N
Mine came installed, so I can't comment.

Gizmotoy | September 11, 2013

@Thomas: Same. I track my Evo, one of the cars that comes stock with those huge structural load-bearing wings, and I could barely notice the difference with it removed even at 140mph.

Glad you like it, though, and that they grabbed you one for free.

eddiemoy | September 11, 2013

i think it makes a big difference when the car has such a low drag coeff... with the low drag, i guess there is a lot of lift. similar to what happen with the audi tt first gen... when they went fast, they were flying literally. they had to put spoilers on them to keep them safe.

jat | September 11, 2013

The diffuser at the back generates far more downforce than the lift from the rear, and the spoiler has minimal impact, according to Tesla's own statements (going from slight positive to slight negative lift). I have had my S85 (no spoiler) at the track, and even at over 100mph, coming over a crest, in an Eau Rouge-like turn where the weight shifts heavily on the rear, and the car never felt even remotely unstable.

If you like the looks, great -- just don't think it has any real impact on lift.

simplesolarinc | September 11, 2013

placebo effect?

Dramsey | September 11, 2013

I'm confused: so you ordered the car without the spoiler, and then decided you wanted it after the price increase, so they gave you a $1500 item for free and installed it, too?

How does that work, anyway?

jat | September 11, 2013

I presume he has a P85 which included it for free, but he declined to have it installed, then changed his mind after they started charging for it.

carlk | September 11, 2013

It must be awfully hard to do controlled test under exactly the same road and wind conditions. Anyway it's worth it even it's only placebo effect for you. ;-)

eddiemoy | September 11, 2013

i changed my mind when they put in what the spoiler actually does and in their own admission, the sales staff wasn't given the correct info on what the spoiler does. if you go and look at the blurb now it says reduces lift by 77% and improves highway stability. it feels rock solid now at above 80mph, not placebo.

it is precisely the kind of misinformation that you guys are talking about that made me for go the spoiler in the beginning. everyone said it has minimal impact. so f'ing wrong!

nickjhowe | September 11, 2013

They say it reduces lift by 77%, but they don't say what the absolute lift is without it. E.g., Say the car only produces 10N of lift normally, then with the spoiler it would produce 3.3N - but both figures are negligible. I've never seen a lift figure published.

DouglasR | September 11, 2013

They apparently redesigned the spoiler. If it was six-months back ordered when you called, and they found one at the service center, maybe it was the original version, not the redesigned version. Which might also explain why you got it for free.

I haven't looked closely at them, so I don't know how they differ. Did they tell you they were giving you the new version?

Thomas N. | September 11, 2013

By most accounts, both internal and external, the effect is negligible. It's a cosmetic item.

Most likely all effects are placebo, which isn't necessarily a bad thing.

eddiemoy | September 11, 2013

another thread earlier mention there was no redesign, this is the same spoiler... they just started publishing the benefits after they separated it out.

i have the matte one.

jat | September 11, 2013


2/ The spoiler takes the car from a small amount of rear lift to a tiny amount of down force (~3kgf at 130mph), but, either way, the loads are still tiny compared to the weight of the car.

Ie it is like having a 3kg of extra weight on the rear of the car. If you think you can feel that on a 4700lb car, you are better than I am.

eddiemoy | September 11, 2013

@jat, you don't know what the lift was before, so it could have been 200lbs of lift in the rear.... so going from 200lbs of lift to 3kg of down...

i definitely feel a big difference at high speeds. not in my head.

Thomas N. | September 11, 2013

I used to work for TRD and we had tons of testing and wind tunnel experiments with rear spoilers. The final determination was that even with an elaborate spoiler design you would need speeds in excess of 150mph to notice any difference.

With the size of the Tesla rear spoiler and the speed limited to 130mph it is completely impossible to notice a difference.

If anybody from Tesla ENGINEERING were to tell you otherwise I would definitely like to speak to him about the evolution of spoiler design and physics.

jat | September 11, 2013

@eddiemoy - I am glad you are happy with your free spoiler.

carlk | September 11, 2013

Guys op is the only person here who has driven the same car with and without the rear spoiler. You don't need to believe him but you can't outright discount it unless you had the same experience.

From Tesla's description I can't believe the spoiler is there for show only either.

@Thomas N. 150mph? Give me a break!

lph | September 11, 2013

Rather than try to pooh pooh the claim lets ask if the spoiler could do something to help at highway speeds as Tesla and eddimoy state. I know from bridge design that eddies can do alot to destabilize and cause a much larger effect dynamically than a simple static force could. Could it be that the spoiler somehow causes (or reduces) eddies to the sides of the car that help stabilize it at speed? This would not be extra down force per'se that is causing the extra stability like in a racing car. In racing a spoiler is primarily used to increase the effective vertical force on the wheels relative to the mass of the vehicle thereby increasing the the lateral g forces obtainable. I believe that the Tesla spoiler is more about stability and not about increasing g forces.

toby_wan_kenoby | September 12, 2013

.....talking about that made me for go the spoiler in the beginning.

@Brian H
I gave you a day to spot this and comment on it. Herewith you forego any right to call yourself the MASTER CORRECTOR.;-)

Brian H | September 12, 2013

Yeah, the brain auto-reversed the words → "go for". 'Course the rest of the post then didn't make sense ...

There are lots of 1\2 word errors. A super-common one is using "setup" as a verb, instead of "set up". 'Everyday' is even more frequent.

chrisdl | September 12, 2013

You're reading Jerome's response wrong.

Jerome Gullen says that INSTEAD OF the lift there is without the spoiler, there is a 3kgf downforce with the spoiler.

x kgf lift - y kgf spoiler's downforce = 3 kgf downforce total (about 30 N)

So the spoiler gives y kgf downforce, not 3 kgf.

In fact, the third question is more appropriate and could explain what eddiemoy feels:

Q: 3. Do you know approximately at what speed the spoiler effect will be significant?

3/ The design goal for the spoiler was to eliminate aerodynamic lift from the car, and thus keep the aero input to the handling balance unchanged regardless of speed. It shouldn’t be that an affect appears, so much as one *doesn’t appear*, since now no lift will be generated at high speeds.

AmpedRealtor | September 12, 2013

@ Dramsey,

I think eddiemoy's experience is similar to my own. I ordered a P85 prior to the big option change of 2013. In our configs, the spoiler was an included item which we could opt out of receiving. When Tesla changed the options, the previously "free" throw-away spoiler now had a $1,500 value attached to it. So I contacted my DS and requested the spoiler be added back into my config.

Dramsey | September 12, 2013

Ok, I understand now...

carlk | September 12, 2013

My Porsche Cayman S has a retractable spoiler. It deploys at 75 mph and retracts back when slowed down to 55 mph. That should give you some idea at what speed Porsche think the spoiler is useful. You can also argue it's not added just for the look since it is retracted most the times. There is a switch that allows you to raise it full time but I have not seen many people doing that on the street.

Same as low profile tires many people get them for aesthetic reasons but you can't deny the performance aspect of them. Some people here are trying just a little too hard to justify why they don't have/want them in either cases.

Eddie, Thank you for helping me to spend that $1500 that I have to spend now.

Haeze | September 12, 2013

Comparing a spoiler on an ICE to one on a Tesla is not even a valid argument.

To anyone who knows how the wing of an airplane works, you will know that the design of the Tesla actually is very similar.

In an airplane wing, the way it stays aloft is that the air moving over the top of the wing has to travel further than the air going under the wing to end up in the same place. This means the air moving over the top of the wing is moving faster, and therefor has a lower air pressure than the air under the wing. The difference in air pressure exerts a force on the wing, pushing it higher vertically. The design of the Tesla is very similar, a flat bottom, and a curved surface on top causes the same effect. This lightens the car as it travels faster. Even a small spoiler at the rear is the equivalent of raising the ailerons at the back of a wing slightly. You maintain the same upward force in the front of the wing, but now you have a downward force on the back of the wing, causing the rear of the aircraft to be forced downward... just like in the Tesla at high speeds.

The reason this is not comparable to an ICE, is that the bottom of an ICE is all tubes, wires, holes, dips, and troughs. The air underneath an ICE car gets disrupted so much, it will nearly always be moving slower than the air going over the roof, which means it is exerting a downward force on the car already. You need a MUCH bigger wing to see any appreciable difference in the amount of downforce.

cwmenne | September 12, 2013

I also added the spoiler to my MS after about 3,000 miles without it and I have tried to evaluate the difference and other than placebo effect (I can talk myself into thinking there is a difference), I can't tell the difference. Being a flight test pilot as my day job, I am pretty used to objective comparison and know a thing or two about aerodynamics and efficiencies and I can't see how it could make a noticeable difference. Even a measurable difference would be difficult and hard to prove. With aircraft, it is very difficult to prove a 0.5 to 1% improvement because it is in the repeatability scatter. I suspect the spoiler is the same (we're talking 1/10 of one percent here). I'm sure it does something in a CFD program (theoretical), but to measure it in real conditions would be impossible. So, enjoy it for cosmetic reasons, but don't expect any more than that.

chrisdl | September 12, 2013

You really should take a peek underneath a modern ICE car.
In fact, my 7 year old BMW 3-Coupe (not that modern) has a totally flat bottom over the full length of the car.

carlk | September 12, 2013

@cwmenne Could you elaborate a little at up to what speed you don't feel the difference? Thanks,

NomoDinos | September 12, 2013

Carlk - can you disable the spoiler on your Cayman? Maybe you could do a little bit of real-world, back to back testing for us at speed >:)

carlk | September 12, 2013

Unfortunately there is no such switch unless if you pull a fuse or cut a wire.

BTW the Cayman design is more like the wing that creates down force while the MS spoiler is to prevent airflow to rear from going down to under body that causes lift. Tesla's description is very clear of that. I'm not sure which is more effective and at which speed. I would think the wing is effective at very high speed since it was first used in F1 race cars. The fact that it's also popular with ricer cars is inconsequential of course. ;-)

cwmenne | September 15, 2013

@carlk, I have been up to about 90mph, with and without the spolier and can't tell the difference either way.

Another more definitive way that I have noticed that the spoiler cannot actually do anything is that I was driving in the rain yesterday and while I was quite impressed at how aerodynamic the front and sides of the car seem to be, I had water drops on my rear window that didn't move at all, even up to 80mph. For those that are not as familiar with aerodynamics; if the water drops aren't moving, that means that the airflow on the rear window is not "attached", which means that there is not laminar flow running down the back of the car and given how small the spoiler is, it couldn't possibly be doing anything significant. The airflow at the top of the 1/8" water drops is essentially zero, so even at 1" off the glass, it is not likely to be very fast either and since the spoiler only sticks up about an inch or so, it simply can't be doing anything. I am sure if I tufted the back of the car, the strings would be dancing around, not an organized smooth flow, which is what the spoiler would need to be effective.

Thomas N. | September 15, 2013

With a 4600 pound car and a two-inch high spoiler you're not even going to notice any effects at the maximum regulated speed of 130mph in this case.

cwmenne | September 15, 2013

@Thomas N, AGREED! :-)

The OP was told by Tesla that there was "77% reduction" in lift. Depending on how they are quantifying that, it could be true, but a 77% improvement on nothing is still nothing, which is about what I expect it actually is. Those that think they can feel something are falling prey to the placebo.