Tesla Semi “Aero Ears” Not Functional In Rocklin Videos

Tesla Semi


Tesla Semis

Tesla Semis reportedly charging at the Rocklin Supercharger station

The gap between the Tesla Semi tractor and trailer seems to have increased as seen at the Rocklin Supercharger station.

In a previous article we showed that the Tesla semi has a very unique feature to reduce aerodynamic drag. This drag reducing feature reduces the gap between the tractor and trailer. It also appeared to move during the reveal video. A secondary reason for the “movable” part is to keep the tractor from hitting the trailer when the trailer is cocked at a large angle.

MORE INFORMATION: Tesla Semi Tractor Appears To Have “Electric Aero Ears”

Tesla Semi

Figure 1

Tesla Semi

Figure 2

A YouTube video (below) of the Rocklin Supercharger shows the trailer making a sharp right turn, and it appears that the panels are not moving. It also appears that the gap between the trailer and the tractor has increased compared to what was shown in the reveal.

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Here’s the gap at the reveal:

Tesla Semi

Figure 3

Here’s the gap as seen at the Rocklin super charger:

This larger gap would tend to reduce range. We are not sure why Tesla has removed the movable feature and increased the gap. Perhaps it was a reliability issue … or maybe this feature has just been temporarily disabled?

What do you think?

Thanks to my engineering partner Keith Ritter (aka HVACman) for spotting this.

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20 Comments on "Tesla Semi “Aero Ears” Not Functional In Rocklin Videos"

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It has grown mirrors too.

Dr. Miguelito Loveless

Mirrors are expected since you cannot legally drive a truck on the road without them. Hopefully the law will soon be amended.

It looks like either the turn wasn’t sharp enough, or the gap was wide enough between the cab and trailer that they didn’t have to move. Sensors in the camera ears probably determined that. I don’t think they’d bother to move those aero flaps during the reveal just to show them off, and then say nothing about them.

“aero ears” are the same size as before, the trailer is maybe different

Ack! You’re absolutely correct. Comparing the photo I linked to in a comment below vs. the “f4” photo in the article above, it does look like the Aero Ears are exactly the same width. So the conclusion I gave in my comment below was flat wrong. 😳

That being the case, it looks like Tesla needs to redesign those “ears” so they will extend or retract, front-to-back, to better fit the actual trailer being used.

Dr. Miguelito Loveless

Like airplane flaps.

Or have the gap between the cab and trailer decrease as you speed up. Once you up to highway speed you won’t be making any sharp turns.

The kingpin is just adjusted farther forward in the reveal video. It is adjustable front-to-back for managing the front-to-rear weight balance of the tractor. Axle weight ratings are very important in the trucking industry and the DOT has specific requirements.

If you follow the body lines of the truck, the aero deflectors are the same in both pictures. The difference in kingpin positioning looks to be about 6” farther back in the recent sighting at the Supercharger site. This would put more weight on the rear axle of the tractor.

I understand what you are saying, I personally don’t know much about trucks so I didn’t want to say that the trailer is shorter or that it is pinned further away from the cabin with too much confidence. But it seems that I was right.

The very tight fit shown in Figure 3 does not appear to me to be practical. Just driving down the road, if the truck hit a bump, that would crush the “Aero Ears” at least a bit before the mechanism had time to react, even if it reacted very quickly. Here is another shot from the Reveal which appears to me to be a more workable, more practical gap: https://tctechcrunch2011.files.wordpress.com/2017/11/tesla-semi_24.jpg The last photo above, Figure 4 (or rather “f4”), does indeed show a wider gap, and quite possibly fixed panels rather than swinging panels, as this article claims. One does not have to be Einstein to figure out that they must have had some problem with the “Aero Ears”, or they would not have replaced them with narrower ones resulting in a wider gap, and therefore higher drag. So what is the problem? My guess, and of course it’s only a guess, is that they found that actual over-the-road driving resulted in greater and/or faster movement by the trailer, in terms of pitch, yaw, and possibly roll, than the Aero Ear actuators could compensate for. So, back to the drawing board for the Aero Ear system! * * * *… Read more »

Or not! Thanks to Stanislav for his comment above, correctly pointing out that it’s not a case of the “Aero Ear” panel being wider, it’s a case of the front of the trailer being further back than we saw at the Reveal. Most likely it’s simply a different trailer. Note the red stripes along the bottom of the trailer shown in the “f4” photo above; no such stripes are present on the trailer at the Reveal.

It doesn’t require swapping trailers or changing fairings to adjust the gap.

The “5th wheel” where the trailer king-pin connects to the tractor is typically on a slide and can be adjusted forward or backward as appropriate to adjust the trailer position relative to the tractor. This is primarily to help “balance” the weight shared between the tractor’s driver axles and the trailer axles, but also can be used to tweak the “gap” between the tractor fairings and trailer.

re: red stripes. It is possible those markings were retrofitted to make the trailer highway legal. Or it could be a different trailer.

We likely will see various trailers with different construction details being hauled by the semis both for testing purposes just because they are doing some real freight hauling and that can mean swapping trailers at the loading dock to stay on-schedule or to match the cargo requirements.

I used meter and find out that width of aero ears are the same. And i believe that mechanism can react fast enough, but some less important improvements definitely will be made before final product is released.

From article: “Tesla Semi “Aero Ears” Not Functional In Rocklin Videos”


Aero Ears were functional at Rocklin but activated only on the side of the rig needed (the inside-turn side) which in the case of the posted video was on the other side of the rig hidden from camera view.

Probably not. The Semi made TWO turns into the parking lot. First a LEFT turn from the street into the lot (which you are referring to), then a hard RIGHT turn to pull towards the charger stations. Asit makes that sharp RIGHT turn entering it briefly disappears, but reappears while still in a relatively-tight turn. If you zoom on the video, you can see that the right aero ear was still in its “neutral” position. It never flared out, unlike what it did at the reveal in a similar right turn. And it had no need to. The trailer gap is adequate to allow the right front corner to swing by the ear without contact.

At low speed in the city those gaps would be irrelevant. It is Highway speeds where the aerodynamics come into play.
It is early days, highly unlikely every feature is 100% ready for prime time at this stage.

It just looks like the 5th wheel is slid back in its rear position.



So this jumbo is moving and transporting the much needed cargo without smoking/polluting the air.