thanks.. back to the 19's we go

 

In a word, YES. It's worth it. Any power consumption saved ultimately helps the planet.

 

It's not just the aero covers. The 18" wheel/tire combo is significantly lighter than the 19" Sport wheels. Less mass to accelerate, maintain and slow down. It's the combo of the weight and aero cover that increases range.

 

I would agree with that, but there still isn't any data to backup the assumption.

 

The 18" will also ride better than the 19" wheels. More rubber = better ride

 

A reminder:
less rim weight => less energy use during city drives
aeros (less air resistance) => less energy use during highway drives
higher sidewalls of tyres => more comfortable ride (equal rubbercompound and pressure)

narrower tyres => less frontal area and less air resistance

 

I know there have been multiple discussions on other threads about this, but I'd like to discuss FACTS here. What is the real world range difference between:

1) 19" sport wheels
2) 18" aero wheels
3) 18" aero covers taken off
4) Other after market wheels?

I know comfort is pretty subjective, so I don't really wanna go there, but at some point we should be able to come up with a definitive understanding of what the range difference is. There have been many assumptions between 2%-10% range difference, but nothing substantial to backup any of those claims.

Any thoughts of what would be the best way to test this out? I assume we'd have to have apples to apples comparison. Two people charge their cars to 80% and then drive on freeways/side roads at a certain speed for a certain amount of miles?

 

There are two main components:
component 1) aerodynamic drag. 19" vs 18" without covers are similar, though not the same. 19" vs 18" with covers are very different. But this difference is mostly noticeable at high speed (not city driving) - more than 5% is expected in this configuration (tire blend included)
component 2) tire rolling resistance. Not about factory wheels but about tire itself. Of course any tire with correct size can be mounted. So YMWV according to how flexible/sticky the blend is. Is not speed dependent.

Model 3 ride is not soft on neither wheels. And it is definitely stiff on 19". This has been confirmed by many owners.


*if you have emotional distress with word "stiff" - replace it with "sporty".

 

Check out this video. The consumption was 270 Wh/mi with 18" aero covers on and 282 Wh/mi with 18" wheels aero covers off. That means without the covers, it was (282-270)/270= 4.4% higher.

 

This is awesome and exactly what I was looking for! Thanks for bringing it to my attention! Now if someone could do an identical video between the 18s and 19s that would be awesome!

 

Based on the coefficients (that are calculated by a "coastdown" test) in the document and the formula:

Drag = (speed*A + speed*B^2 + speed*C^3)/375

i tried to calculate drag at different speeds. The difference in percent seems to be almost constant regardless of speed. Does it look right?

 

Btw: I guess we cant be sure that the 18 inch profile is in fact WITH the aero cover?

 

The aero wheels with covers and the sport wheels are the two configurations that Tesla sells, so I think it makes sense that it would correspond with the two configurations in the document provided to the EPA. Couple that with that comment from a VP of engineering about a 10% difference between the wheels, and I think it's a safe assumption that the 18" configuration is with the aero covers.

 

Check out this thread, if you haven't already seen it. @Troy does some calculations as well. There are a couple of other threads on TMC. The one I've been trying to find had a graph of energy consumption/mile vs speed based on the road load hp and coast down measurements. I can't find it (still looking). But from what I recall, as speed increases, the difference between 18s and 19s diminishes.

https://teslaownersonline.com/threads/range-of-the-tesla-model-s-x-3-at-65-70-75-80-mph.5496/

 

Someone beat you the punch up above. Great video and I would guess that Sport wheels will be slightly worse than 4% range loss, but probably not that much worse. This is me completely throwing out guesses, but I would guess that Sport wheel's design will actually be more efficient than aero without covers, but the weight/size will make it less efficient than the aero without covers. The big question is, will the more aerodynamic design make up for part of the weight/size difference or is there going to be a big hit to range still?

 

I didn't want to write in this thread about something else other than actual tests like in the video but probably I should clarify the current situation. @Agon's numbers a few messages ago are same as mine. The data on the EPA document shows 10.7% higher consumption with the 19" wheels compared to 18" at 70 mph. However, it is unclear whether 18" is with or without aero covers. There are two options:

Option 1: The 10.7% difference based on EPA data is between 18" wheels with aero covers and 19" wheels. In this case, the situation looks like this:

• 104.4% = 18" -aero vs 18" +aero
• 106.3% = 19" vs 18" -aero
• 110.7% = 19" vs 18" +aero

Option 2: The 10.7% difference based on EPA data is between 18" wheels without aero covers and 19" wheels. In this case, the situation looks like this:

• 104.4% = 18" -aero vs 18" +aero
• 110.7% = 19" vs 18" -aero
• 115.1% = 19" vs 18" +aero

I don't know which option is correct. We need to wait for somebody to test it.

 

Check out this thread on reddit



Some insight into the 18" aero design from the (former) head of aerodynamics at Tesla, Robert Palin

https://www.linkedin.com/in/robert-palin-2127ab6/

For the lazy:

Comment 1: I was the head of aero at Tesla for MS, MX, and M3, and I can confirm that wheel design & size can be the biggest influence of all on the aero efficiency of a road car. The aero, design, and chassis teams put a huge amount of effort into these wheels, and they do really work!

Comment 2:
With casting there's a minimum thickness of 10-12mm at the perimeter, making wheels like this obscenely heavy. With the cap approach they're the lightest wheel design Tesla has ever done, & with very low rotational inertia. A lot of effort went into the integration of the cap so that it sits flush at the rim, and not on the outside if it, as on all the other wheel caps you'll see. Having multi-part & multi-material wheels is the best way to satisfy multiple optimization goals. The thought with these wheels that having the latest tech on the latest car would be more appropriate than more traditional rims.

Comment 3: The 'skeleton' wheel underneath is still alloy, but the shape comes entirely from strength & mass optimization (the hard work of a talented Canadian engineer named Steve). The colour was also originally a bright silver, but the dark grey was preferred by the Powers-That-Be (not by me).

Comment 4: The aero benefit increases very strongly with speed, as the power requirement to overcome aero resistances increases with the cube of speed. I.e. if you go twice as fast, you use 8x the power. That said, aero is a small percentage at city speeds, where mass & rolling resistance dominate. The 2-part design of the aero wheels allowed the underlying rim to be super-light, which will also help in the lower speed stuff.

Other comment he posted in a group about Aero wheels on the S:

Likely never, I'm afraid. The original base 19" wheels for MS were supposed to have transparent plastic "flower petal" caps to close the larger gaps between the spokes. However, the tooling for those rims was the very first that was completed, and did not include provision for retaining the caps. That, plus concern over rattling, and yellowing of the plastic over time killed the idea. All that said, the "Slipstream" wheel design that became standard on MS (19s) & MX (20s) is aerodynamically excellent, & yielded >50% of the benefit of the original Aero wheels (RIP!) with lower mass & less controversial aesthetics!

 

Do we know definitively, whether the EPA Rating of 334 was with 18” wheels and the Aero covers? I have never seen anything that clearly states this.

 

@ng0 , you need to amend your poll question to define more precisely what you mean by "range difference".
I assume from the discussions so far, and some of the rudimentary testing vids seen, that we're talking about steady-speed highway driving where the only really significant factor is going to be the aero properties of the wheel (I exclude tire here as both sizes offered use the same width). However as has been noted in this and other threads, the weight will be a far more significant factor in lower speed stop-and-go driving. Based on the data I've seen so far the aero differences between the two sizes/styles offered are much more significant than the weight differences. There will also be some minor variables due to the rolling resistance properties of the two different tires, however as both are LRR designs I don't think that will play a huge factor.
But we need to know which type of range - city, highway, or a mix - we're talking about before we can offer any kind of valid guesses.

 

Good point. I can't update the poll, but for anyone confused about this, just assume a mixed/average range. I'm not really sure what that would mean, but I guess some combination of normal freeway/city driving.

 

There are numerous variables that will magnify the effect of the aero wheels. Obviously faster speed but smaller variables like colder temperature and lower altitude. Basically anything that increases air density will show more of a benefit from improving aerodynamics.

And low atmospheric density makes aerodynamics less important. That's why the Borg Cube shape is irrelevant in the vacuum of space.

 

Borg Cube....LOL, now it all makes sense, that's how Elon got to earth from Mars. Resistance is futile, you will all be assimilated to electric cars!

 

I saw that skit live and never laughed so hard in my life.