20-ish mile range difference between 5 seat and 7 seat Gravity?

[illopp00]

If you can find a selection of summer performance tire sets that will fit the 22/23" wheels, I'd certainly like to know about it. As I said, the Michelin Pilot Sport 4S will fit if you are okay with different speed ratings and an EV/nonEV tire split between the axles.

I'm not being sarcastic. I really would like to get comfortable that tires won't be exceptionally tricky to find for those wheels.

I did have to manually plug in the sizes, but it looks like Aston Martin spec summer Pirelli PZero PZ4 summers? It's a little sketch, they may be similar to DBX tires, but the load rating may not be sufficient, we don't know the Gravity curb weight, although I have optimism that it might actually just be under 6000 lbs (Touring being 400 lbs less than GT). Otherwise putting summers on the 21/22 would be significantly easier since JLR seems to use them on performance SUVs. It's like mutant of Land Rover fronts and Aston Martin Fronts. Seems too early to speculate and find this stuff. Only thing I can see is that the 22/23 are going to be seriously expensive replacement rubber relative to standard Hankook EV stuff....

 

[flarbear]

Pure speculation here, but I'm guessing it's some kind of rack and pinion device driven by a motor placed between the floorboard and the bottom of the seat cushion. It wouldn't require a large motor, and there should be room for it there.

A better picture of the mechanism in this photo from reddit: https://www.reddit.com/media?url=ht...bp&s=92b7d46b4b47b487f57c52ff703a0de94355fe5d

That looks like a fairly deep mechanism, requiring at least an inch of floor space, maybe 2?

 

[Kirby]

The 130# seat weighs 500#
In post 112 it mentions:
https://www.epa.gov/system/files/documents/2022-12/420r22029.pdf

Worth noting is that the dynamometer testing is in 500 pound increments. The extra seat weighs something like 130# in real life, but I heard that it puts the Gravity over a 500# boundary. The five seat car weighs 500 pounds less as far as the dyno is concerned, not 130. I've seen the Gravity weight as just under 6k for 5 seats and just over 6k pounds with seven. One version of the car is getting a bonus or the other is getting screwed, take your pick. In real life, they should be close in actual range.

Page 26:
"All vehicle weight data in this report are based on inertia weight classes. Each inertia weightclass represents a range of loaded vehicle weights, or vehicle curb weights7 plus 300pounds. Vehicle inertia weight classes are in 250-pound increments for classes below 3,000pounds, while inertia weight classes over 3,000 pounds are divided into 500-poundincrements."

 

[AnthonySF]

Remember, the range difference has nothing to do with the size of the wheels. It has to do with the type of tires. If they have a larger contact patch or made of a stickier material, they create a little bit more resistance and therefore exact a range penalty.

That’s incorrect. Wheel size most certainly plays a part in efficiency regardless if it’s a EV or ICE. So, Lucid is clearly lying here, with the 21/23 and 22/23 setup getting the same range.
I put non ev tires on 20’s on my Rivian and they were 7% more efficient than the 21’s with an ev tire on my Rivian.

 

[037]

That’s incorrect. Wheel size most certainly plays a part in efficiency regardless if it’s a EV or ICE. So, Lucid is clearly lying here, with the 21/23 and 22/23 setup getting the same range.
I put non ev tires on 20’s on my Rivian and they were 7% more efficient than the 21’s with an ev tire on my Rivian.

It’s not just tire size but also wheel weight. And friction from tires. Guessing they are just being cautious with 21/22 as opposed to lying.

 

[AnthonySF]

It’s not just tire size but also wheel weight. And friction from tires. Guessing they are just being cautious with 21/22 as opposed to lying.

I did not say tire size is the only thing that matters. I responded to another post stating wheel size is irrelevant. It’s not, watch the video in my post and you will learn why.
Obviously weight plays a part in this too. And larger wheels weigh more than smaller wheels. So your point?
Cautious would not be the word I would use as something is incorrect. The 22/23 setup is heavier and less aerodynamic than the 21/22 setup, which will make it less efficient. Why would Lucid be the only EV manufacturer that when you change the wheel size on their website, you can get the same range. Why doesn’t Tesla do that? Or Mercedes? No tire can makeup for physics.

 

[hmp10]

So, Lucid is clearly lying here, with the 21/23 and 22/23 setup getting the same range.

This is not uncommon. Tom Moloughney discussed this in his recent range test of the Cadillac Optiq which gives the same range rating on its Monroney stickers for all trims of the Optiq even though they have varying wheel and tire sizes. He added that some other manufacturers do the same thing.

So if Lucid is "lying" here, they have a good bit of company.

 

[Elfin]

And of course EPA range is not a very useful metric for most of us who only care about range when driving on the highway.
Normally I like Engineering Explained videos but he doesn't actually present any explanation for why larger diameter wheels are less efficient!
The primary reasons for the range difference on the Tesla Model 3 is that the 19" wheels don't have aero covers and the 20" wheels have sticky tires. I do agree that super low profile tires are dumb for other reasons...

 

[AnthonySF]

And of course EPA range is not a very useful metric for most of us who only care about range when driving on the highway.
Normally I like Engineering Explained videos but he doesn't actually present any explanation for why larger diameter wheels are less efficient!
The primary reasons for the range difference on the Tesla Model 3 is that the 19" wheels don't have aero covers and the 20" wheels have sticky tires. I do agree that super low profile tires are dumb for other reasons...

Yes, he does explain why…the whole video is about it. No, the primary difference is not aero caps. Smaller wheels are more efficient applies to ICE cars as well, go look up for yourself. Tire size the same, a 19 inch wheel will be more efficient than a 20 inch wheel of same design. A smaller wheel has thicker sidewall, which is more aerodynamic than a wheel with openings for aesthetics or brake cooling.

 

[hmp10]

And of course EPA range is not a very useful metric for most of us who only care about range when driving on the highway.

Yes. Publishing 75mph range test results such as "Car & Driver" does would be far more useful for most EV drivers when doing comparison shopping. (I like the "Car & Driver" tests better than Tom Moloughney's 70mph tests because DOT studies have shown that highway speeds on U.S. interstates are around 78mph.)

 

[hmp10]

A smaller wheel has thicker sidewall . . . .

Huh?

 

[AnthonySF]

Huh?

Guys and gals, it’s not that hard. Tire size the same, smaller wheels are more efficient. Smaller wheels are lighter and more aerodynamic because with a smaller wheel, you need a thicker sidewall. What is more aerodynamic cutting through the air? The flat sidewall of a tire or the various openings of a wheel?

 

[Adnillien]

Normally I like Engineering Explained videos but he doesn't actually present any explanation for why larger diameter wheels are less efficient!

Yes, he does explain why…the whole video is about it. No, the primary difference is not aero caps. Smaller wheels are more efficient applies to ICE cars as well, go look up for yourself. Tire size the same, a 19 inch wheel will be more efficient than a 20 inch wheel of same design. A smaller wheel has thicker sidewall, which is more aerodynamic than a wheel with openings for aesthetics or brake cooling.

Actually he does NOT present any physics based reason for the difference with wheel diameter. He presents three quadratic equations provided by Tesla and uses the resulting math to show a difference in efficiency. I would prefer a physics based explanation.

 

[Elfin]

Yes, he does explain why…the whole video is about it. No, the primary difference is not aero caps. Smaller wheels are more efficient applies to ICE cars as well, go look up for yourself. Tire size the same, a 19 inch wheel will be more efficient than a 20 inch wheel of same design. A smaller wheel has thicker sidewall, which is more aerodynamic than a wheel with openings for aesthetics or brake cooling.

What is the primary difference other than aero wheels and tire compound? It is possible to make larger diameter aero wheels...
Obviously if the smaller diameter wheels have tires with a narrower section width that will help with aero but then it's not an apples to apples comparison.

 

[hmp10]

Guys and gals, it’s not that hard. Tire size the same, smaller wheels are more efficient. Smaller wheels are lighter and more aerodynamic because with a smaller wheel, you need a thicker sidewall. What is more aerodynamic cutting through the air? The flat sidewall of a tire or the various openings of a wheel.

Tire sidewall thickness might affect sidewall stiffness and therefore rolling resistance. It has nothing to do with aerodynamics.

If you meant sidewall height, that also does not affect aerodynamics. In either case, you should master the subject matter over which you’re being so condescending to other posters.

 

[hmp10]

Sidewall height, taken alone, does not affect aerodynamics. It does in conjunction with wheel diameter if rolling diameter remains the same as increasing sidewall height offsets diminishing wheel diameter, but even then only to the extent of the difference in the surface characteristics of the sidewall and the wheel. In practical terms, the small difference in wheel diameter between a 22” and a 23” wheel is going to be overwhelmed by other factors at play: tire rolling resistance, wheel design, tire cross section, etc.

 

[Elfin]

Tire sidewall thickness might affect sidewall stiffness and therefore rolling resistance. It has nothing to do with aerodynamics.

If you meant sidewall height, that also does not affect aerodynamics. In either case, you should master the subject matter over which you’re being so condescending to other posters.

Something I noticed about the factory tires on the Model 3 18" aero wheels is that the tread width is narrow relative to the wheel width which probably gives it a more aerodynamic profile. The tread width is actually 1.3" narrower. I think the real conclusion is that manufacturers optimize the small wheel/tire combination for efficiency and the large wheel/tire combination for maximum traction. If both were optimized for efficiency I bet they would be very close.

 

[Knucklehead]

Actually he does NOT present any physics based reason for the difference with wheel diameter. He presents three quadratic equations provided by Tesla and uses the resulting math to show a difference in efficiency. I would prefer a physics based explanation.

Yeah, that video annoys the crap out of me.

He has a good start with the analysis of the aerodynamic impacts of tire width. That seems like a solid analysis. Then it goes downhill.

The rolling resistance analysis is pretty good, but then he makes it sound like the average tire has good rolling resistance so there is little room for improvement there. That is BS. Maybe if you have a stock Tesla tire the rolling resistance is good, and hard to improve on, but a standard non EV specific tire does NOT have good rolling resistance. And it is very difficult to know without testing how good rolling resistance is.

And finally, he totally craps the bed with the wheel size analysis. He compares three different tire and rim combinations and concludes smaller wheels are better. All three wheels have different tires, different wheel widths and different designs that greatly impact aerodynamics. But he just says smaller is better. Which is not true. And he does not explain why larger wheels are less efficient.

And then he tells us we hate the environment if we have big wheels. So annoying.

The fact is bigger rims with tires that have smaller sidewalls usually perform worse because of aerodynamic losses due to the wheel rotating and moving forward. Two different factors. The sidewall of a tire is smooth, so it has a less rotational resistance at high speeds when compared to a rim that has open areas to catch the air. But you can design a rim that has minimal aerodynamic losses and is better than a smaller wheel that isn't as aerodynamic. It is aerodynamics that matter, not wheel size.

By the way, he also misses the correlation of wheel width and rolling resistance. I agree width has a minimal impact on aerodynamics, but 50% more rubber on the road would reasonably have a significant impact on rolling resistance.

I wish people would top posting the video like it is some great analysis that provides real answers. It isn't.

And, by the way, my Rivian has 22 inch rims which are more efficient than the 20 inch options provided by Rivian. So obviously rim/wheel size isn't the most important criteria.

 

[037]

Yeah, that video annoys the crap out of me.

He has a good start with the analysis of the aerodynamic impacts of tire width. That seems like a solid analysis. Then it goes downhill.

The rolling resistance analysis is pretty good, but then he makes it sound like the average tire has good rolling resistance so there is little room for improvement there. That is BS. Maybe if you have a stock Tesla tire the rolling resistance is good, and hard to improve on, but a standard non EV specific tire does NOT have good rolling resistance. And it is very difficult to know without testing how good rolling resistance is.

And finally, he totally craps the bed with the wheel size analysis. He compares three different tire and rim combinations and concludes smaller wheels are better. All three wheels have different tires, different wheel widths and different designs that greatly impact aerodynamics. But he just says smaller is better. Which is not true. And he does not explain why larger wheels are less efficient.

And then he tells us we hate the environment if we have big wheels. So annoying.

The fact is bigger rims with tires that have smaller sidewalls usually perform worse because of aerodynamic losses due to the wheel rotating and moving forward. Two different factors. The sidewall of a tire is smooth, so it has a less rotational resistance at high speeds when compared to a rim that has open areas to catch the air. But you can design a rim that has minimal aerodynamic losses and is better than a smaller wheel that isn't as aerodynamic. It is aerodynamics that matter, not wheel size.

By the way, he also misses the correlation of wheel width and rolling resistance. I agree width has a minimal impact on aerodynamics, but 50% more rubber on the road would reasonably have a significant impact on rolling resistance.

I wish people would top posting the video like it is some great analysis that provides real answers. It isn't.

And, by the way, my Rivian has 22 inch rims which are more efficient than the 20 inch options provided by Rivian. So obviously rim/wheel size isn't the most important criteria.

Wheel weight is generally the biggest factor, the road contact patch, rolling resistance, wind resistance, kind of in that order.

Lucid Gravity 21” rear is 8.6” contact patch to road, rear 23” is 10” contact, both tires 285 wide.

Food for thought.

 

[AnthonySF]

And, by the way, my Rivian has 22 inch rims which are more efficient than the 20 inch options provided by Rivian. So obviously rim/wheel size isn't the most important criteria.

No shi* your 22” wheels on 33” summer tires are more efficient than the 20” wheel on larger, 34” all terrain tires. It’s not that complicated to switch out the all terrain tires for a 33” 275/60/20 all season tire.
I had the 21” setup with the aerocaps in and averaged 2.31mi/kwh at average speed of 34mph over 5500 miles. Then put on the Rivian 20” AT brights, on 275/60/20 Pirelli AS plus 3 AS tire (not an EV tire) and averaged 2.49mi/kWh at average speed of 36mph over 6k miles. Wow, weird how the smaller wheel with a non ev tire and no aero cap was more efficient than the larger wheel with a ev tire and aero cap. I guess it’s like a tootsie pop, this world may never know.