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Discussion Starter · #1 ·
InsideEV's posted an interesting (at least to me) article about why more cars don't come with more aerodynamic wheels. And of course around town the benefit would be even less.

That said, I'm a little surprised that there aren't at least a few more aero options - even aftermarket (didn't see any on Tirerack). I quite like the Model 3 wheel used for illustration in the article. I'd be reluctant to slap a solid disc on my wheels as I'd worry about heat and debris, but an engineered wheel would get my attention.
 

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I'm a little surprised that there aren't at least a few more aero options.
My old Honda Civic Hybrid (2006 model) essentially had a solid disc wheel cover. But that was about the only place I have ever seen one. Again, as the article noted, they didn't choose to use that feature on other ICE Civics. I thought it was a nice differentiator.
The article was using percentage of benefit, but if it is thought about as reduction of total energy consumption, it should be the same, right?
 

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What is needed is a lighter tire and wheel, if you wanted aero you could use a clear plastic cover over your existing wheel, but I don't think it would help that much with drag.
 

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The Bolt is still a new car and there really haven't been very many of them sold yet.

I'd expect that in the next couple years a few manufacturers will be putting out some aerodynamic wheels, though I don't think we'll have a lot of choices, wheels aren't cheap and any well engineered lightweight aerodynamic wheels will be on the more expensive side of that. Your market is going to be rather limited to people willing to spend $1000+ for new wheels to give them very small boost in efficiency (I'd guess 5% would be a pipe dream)

Honestly I don't even think the Bolt is going to be that appealing to obsessive hypermilers, it's intrinsic aerodynamics are pretty abysmal.
Chevy Bolt: 0.308 Cd
Tesla Model 3: .23 Cd
Toyota Prius Prime: .25 Cd

Now you can argue that the Bolt has more usable passenger and cargo volume and being a hatchback makes it much more usable (all true in the case of the Model 3 at least) but comparing it to other similar sized plug-in vehicles:
Ford C-Max Energi: .30 Cd (The C-Max is larger and has even more room)
Toyota RAV4 EV: .30 Cd (also larger, taller and visually more boxy looking)

**** look at the fully ICE Toyota Sienna, a simply huge vehicle with oodles of extremely usable cargo and passenger volume (nearly 10x the Bolt), with almost enough room in the back to fit an entire Bolt it still almost matches the Bolt in the wind tunnel at .309 Cd.
 

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I think the Bolt is a car rushed into production with one thing on GM's mind, that was to beat Tesla at the 200 mile range game at a lower price point so more people could own a new electric car.

You could have bought a used Tesla with 50 or 100K miles for what we paid for our Bolts but what condition was the Tesla going to be in when and if you could have found one for sale at the price of a Bolt?

From what I saw over a lifetime of buying and selling used cars was many high end cars were beat to death or close to it, when they were offered for sale.
I often heard people say some wealthy guy owned this car this is the one I want, I would explain the way I found most of the cars I bought that were owned by the wealthy.

I would rather own a used car that belonged to someone who cared about getting the most out of their cars, not someone that just used them for a tax write off or having the latest toy.
 

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Discussion Starter · #6 ·
@raitchison - Don't forget that there is a difference between total drag and the coefficient. But yeah, I think my mid-eighties car had a Cd around the 0.3 mark so the Bolt ain't exactly earning prizes :)

As for hypermilers, function would only be part of the equation. There is an element of aesthetics too... some fools may be persuaded to part with their hard earned cash for a little visual differentiation. And I may be a member of that group.

While I was imagining the Bolt as the target vehicle, I don't suppose there's any reason a Sonic, etc couldn't also use an aero wheel, which might increase the potential market a bit.
 

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What is needed is a lighter tire and wheel, if you wanted aero you could use a clear plastic cover over your existing wheel, but I don't think it would help that much with drag.
You've got this backwards. The cover over the wheels does help drag significantly, which decreases energy consumption. The wheel/tire weight has an imperceptible effect on constant-speed power requirements.
I'd expect that in the next couple years a few manufacturers will be putting out some aerodynamic wheels, though I don't think we'll have a lot of choices, wheels aren't cheap and any well engineered lightweight aerodynamic wheels will be on the more expensive side of that. Your market is going to be rather limited to people willing to spend $1000+ for new wheels to give them very small boost in efficiency (I'd guess 5% would be a pipe dream)

Honestly I don't even think the Bolt is going to be that appealing to obsessive hypermilers, it's intrinsic aerodynamics are pretty abysmal.
Chevy Bolt: 0.308 Cd
Tesla Model 3: .23 Cd
Toyota Prius Prime: .25 Cd

Now you can argue that the Bolt has more usable passenger and cargo volume and being a hatchback makes it much more usable (all true in the case of the Model 3 at least) but comparing it to other similar sized plug-in vehicles:
Ford C-Max Energi: .30 Cd (The C-Max is larger and has even more room)
Toyota RAV4 EV: .30 Cd (also larger, taller and visually more boxy looking)

**** look at the fully ICE Toyota Sienna, a simply huge vehicle with oodles of extremely usable cargo and passenger volume (nearly 10x the Bolt), with almost enough room in the back to fit an entire Bolt it still almost matches the Bolt in the wind tunnel at .309 Cd.
I think you might be confusing Cd with CdA. Cd is a unitless coefficient that is shape, not size, dependent. A 747 has a Cd of around 0.03, ten times better than the Bolt EV.

I agree that hypermilers probably won't be too interested in the Bolt EV or new aftermarket wheels. Aftermarket wheels are made for 1) dedicated winter tires or 2) enthusiasts. There aren't many hypermiler enthusiasts that want to spend money on wheels. Financially, it doesn't make much sense to spend hundreds of dollars on wheels to save tens of dollars on electricity.
 

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...You could have bought a used Tesla with 50 or 100K miles for what we paid for our Bolts but what condition was the Tesla going to be in when and if you could have found one for sale at the price of a Bolt?
I bought a Certified Pre-Owned Tesla Model S directly from Tesla. It was a lease return with 33,000 miles on it. They gave me a four year/50,000 mile warranty on all non-drive train/battery components, so the car is covered through 83,000 miles. The car was delivered to me in immaculate shape, and, because of Tesla's OTA updates, it is in many respects a much newer car than the one that was leased in 2013. We subsequently bought a Bolt for my wife for about 80% of what we spent on the Tesla, so it's not exactly an apples-to-apples comparison for money spent.

The 85KW battery pack was originally rated for 265 miles of range. When I fully charge it 45,000 miles later, it shows 261 miles of range, a 2% degradation of the battery pack.

Moral of story (and this goes for Bolts, too) - EV's do not suffer the same deterioration issues that an ICE does. So long as the body and upholstery aren't beat to death, you get a car that performs like new. The battery pack/drive train will be good for hundreds of thousands of miles, assuming proper charging techniques are used to maximize battery life.
 

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I would still prefer having a new never used car over a whatever years old used Tesla, and I have no need for a car that is as big as a model S.

I have had enough used cars, I bought and sold used cars for nearly 40 years, I have owned and used hundreds of them.

I don't want a big car, the only reason I only bought big cars was if I had a customer that would buy it as soon as it was done.

I did much better selling smaller fast cars, only if I had a customer for a large car, I would buy one then do the needed service and repairs while driving it making sure my customer got what he was going to pay for.

A 4 year/50,000 mile warranty on all non-drive train/battery components,

Try using that warranty when the car stops, nothing that makes the car work is covered.
 

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You've got this backwards. The cover over the wheels does help drag significantly, which decreases energy consumption. The wheel/tire weight has an imperceptible effect on constant-speed power requirements.
Right, weight has to do with stop and go. Zero to do with steady state highway cruising. I agree a wheel cover could be worth while.. I mean it depends on what your idea of a worth while % gain is of course. But ecomodder has all your answers. And its not just down to the wheel cover design, how inset the wheel is relative to the body makes a big difference too.

Enjoy the headroom and ease of egress/ingress guys. That is what the Bolt design does well!
 

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Discussion Starter · #11 ·
A 4 year/50,000 mile warranty on all non-drive train/battery components,

Try using that warranty when the car stops, nothing that makes the car work is covered.
I believe the drivetrain warranty carries to the new owner, which I think is 8 years/125k miles from the original in service date. The "extended" warranty covers the other bits, which is nice. I'd like to have all those other bells and whistles covered - like the console, door handles, etc.

We were looking to spend ~$30k on a car, hence the Bolt (after incentives). But to be honest, if I had the wherewithal to afford a $60k car I'd be sorely tempted to buy a used Model S (ala NoMoPetrol). I really like the idea of free supercharging. I noticed on our trip down I-95 that there were no L3 chargers between Richmond, VA and Jacksonville, FL. But there are superchargers.
 

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Enjoy the headroom and ease of egress/ingress guys. That is what the Bolt design does well!
I'm pretty tall @ 6'5" and carry much of my height in my torso so both legroom and headroom are appreciated, though even my 6'8" son fits in the Bolt with 2" of headroom above him (seat width is a whole 'nother issue). The Bolt is simply taller than it needs to be for 99.997% (someone who is 6'9" is in the 99.997 percentile and taller than 1 in ~29,000 Americans) of people. If the car were 2" shorter most of us would not even notice the difference. For that matter I wonder how many people who are taller than 6'8" would fit in the extremely narrow seats, really tall people tend to be a fair amount larger in general than normal sized people.

IMO the extra height was added for one reason only, to enable GM to sell it as a "crossover". At least 1" of the ride height (which also hurts aerodynamics and by extension highway economy) is for the same reason.

Who knows what kind of efficiency we could have gained if GM built the car 1" lower to the ground and with a 2" shorter roof? I'm guessing more than a little.

Poor aerodynamics is actually more excusable to me in a shorter range EV like a Leaf or Fiat 500e, after all very few people are considering taking these on longer drives on highways. On the Bolt a 10% boost in efficiency means an additional ~25 miles in range which could make the difference between making a road trip doable or not.
 

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Discussion Starter · #13 ·
Hmmm, just stumbled on a discussion of the Volt's Cd which would intuitively be lower than the Bolt. Supposedly it's about 0.28. They noted that GM's EV-1 was lower than 0.2 and a Prius was ~0.25. HOWEVER: someone chimed in with the claim that GM had tested a Prius in the same tunnel used for the Volt and it clocked in at 0.3. Because of the hatchback styling and vents needed for the engine, etc, this doesn't seem unreasonable.

Still, I can see @raitchison point on making the car lower to present less frontal area for less overall drag. Maybe there's some advantage to the design - like wasn't the AMC Eagle raised to take advantage of the "light-duty truck" class it could fit into?
 

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Who knows what kind of efficiency we could have gained if GM built the car 1" lower to the ground and with a 2" shorter roof? I'm guessing more than a little.
I agree with that assessment. More height than ideal config for 99% of buyers. I will say this- If you jack the seat all the way up, you get better traffic vision than most small cars can do. Traffic vision (especially with all the huge tall vehicles on the road) can be a safety issue in low cars. Poor vision is an underappreciated contributor to accidents. Also for those transporting elders around, Bolt is better than most cars for not banging grandma's head into the pillar. Probably does cost 10% of range versus a 0.25 car.. but take the good with the bad. Back to the aero wheels, IIRC it is possible to get a percent or two back with them. Various user results are available on ecomodder.
 

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I believe the drivetrain warranty carries to the new owner, which I think is 8 years/125k miles from the original in service date.
I didn't mention that in the original post, but, yes, I still have four years and unlimited mileage on the battery pack/drive train.
 

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If you really want aero covers, the same people that started them still make them 60 years later.

http://www.mooneyesusa.com/Moon-Disc-Snap-On-p/md11-sn.htm

They don't have one that will fit the Bolt, but maybe with enough interest they could make some that fit the 16" Sonic steel wheels. Maybe call them and see if you could get some suggestions from them. In addition, I noticed to day that the Hyundai Ioniq comes with some sort of aero disc cover, maybe they can be adapted.

I think the reason they are not more wide spread in use on all cars is, at the speeds we typically drive, they don't make much difference. People prefer appearance over a .05% (or whatever the actual number is) improvement in fuel mileage/range. If it actually made a big difference, every car, truck and race car would have them. They don't. I believe that the reason some "Eco" cars have these aero covers on is mostly marketing. Some buyers want to see them and feel it makes the car more serious about saving energy.
 

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I think the reason they are not more wide spread in use on all cars is, at the speeds we typically drive, they don't make much difference. People prefer appearance over a .05% (or whatever the actual number is) improvement in fuel mileage/range. If it actually made a big difference, every car, truck and race car would have them. They don't. I believe that the reason some "Eco" cars have these aero covers on is mostly marketing. Some buyers want to see them and feel it makes the car more serious about saving energy.
It doesn't appear that you read the article linked by the original post in this thread. The Model 3 aero caps improve highway efficiency by 4%.
 

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It doesn't appear that you read the article linked by the original post in this thread. The Model 3 aero caps improve highway efficiency by 4%.
You got me. I didn't read the article, but I have now. My points still stand though. The improvements by whatever percentage aren't worth it and likely not noticeable to most people. BTW, the 4% number is a guess for the Tesla, what it would be on a Bolt, who knows?

Like I said though, where there is a will there is a way. If you really want aero covers bad enough they can be made, or adapted. If there were a market for them, they could be manufactured. Sadly, wheel covers, more commonly and incorrectly called "hub caps", are no longer vogue. Today people crave spindly conestoga wagon wheels. The bigger the better and the more brakes and suspension bits we can see through them the better.

Strange world, but it is what it is.
 

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Aero wheels do make a difference for ice and ev cars. You see less of a benefit on ice because of drivetrain loss is much higher. They also lose efficiency with braking. With ev the biggest loss is air resistance since drivetrain and braking is much more efficient. If you don't see them on Race cars is because the regulations doesn't permit them. Formula 1, Lemans, etc.... did use full aero caps in the past, but they were banned. It makes a much bigger difference at high speeds in those cars since they easily touch 300 km/h +. You do see some aero caps on some race cars like ABT Audi team in formula e , some teams in Lemans, but they can't cover more than 50% area of the wheel. Plus in a race car they really push the shape of the body and use winglets, louvers in the fenders to have the air go around the wheel wells so it is not affected by the turbulence of air around the wheels.


If you go on eco modder forum , there is a lot of information and numbers that confirms the improvements in mpg on the highway.
Like you said, most people don't care and are only interested in good looking wheels. Also fabricating an aero wheel in aluminum does take more material. So for a cast wheel which is the cheapest to manufacture makes the wheel much more heavy compared to a wheel with thin spokes. You can do forged, but it is a process that costs much more to do. I think the best method is what Tesla did. Do a regular spoke wheel and add a plastic cover on top. You get two wheels in one. Take off the covers if you are in the city and when you have to do a longer highway trip you put the caps on for better efficiency. With the increase of ev car sales, I'm sure many aftermarket wheel brands will start to sell that setup. ABT did make a proto wheel with an aero cover inspired from their formula e car which was installed on Jon Olssen's car and said they will start selling it soon. I attached some pics of the wheels. It is not a full cover, but its a start.


About the article for the model 3 aero caps, the owner in the video saw an increase of 4.5% over a 17.5 mile highway drive loop with the caps on. Over a 300 mile drive on the highway depending on speeds, winds, temperature you could easily have 20+ miles extra. Some will say its not a lot , but its still better than nothing. It could be the difference between reaching a charger or not. Even if you plan ahead, sometimes it doesn't always go as planned so its good to have extra miles from a simple mod. Tire width and compounds makes a big difference too. Also in the cold, air is denser than hot air so it can make a bigger difference.


For the Bolt, I think you could see the same or higher efficiency since the car is less aero compared to model 3. Lowering the suspension on the Bolt would also help aero. How much? Owners will have to test it to find out.
 

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I was hoping there were ready-made solutions that didn't require drilling or epoxying moon discs to wheels. If there were a set of moon discs that attached to the lug nuts somehow, I'd probably spring for a set if under $100 would buy me 5-10% increase in range.
 
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