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Hey redpoint5, unless I have misunderstood your point, you make an interesting case for perpetual motion. I would rather not start discussing a comparison between the motion of a rocket travelling to the moon and the motion of a car travelling on earth, as I don't believe they are comparable. But if I take your interpretation of the physical world, then I might ask why a spinning top will eventually come to rest?
Friction. Both through air resistance and through the top's point of contact with the surface below. In space, with no resistance, the top would spin forever, and that would be true whether it was light as a feather or as heavy as an ocean liner.

The same is true of the wheels on a car. Once they're up to speed, their mass is irrelevant in terms of maintaining their angular momentum - the only thing that matters is bearing friction, air resistance, rolling resistance, and other frictional losses.

Now I suppose you can argue that on a rough surface where the suspension is being given a workout, the lower mass of the wheels might translate to a lower rolling resistance because the wheels would conform more easily to the undulating road surface. But even if that was true it would be pretty negligible compared to the other losses.
 

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I had 10 pounds wheels on my little 90hp track car back in the day. The stock wheels were 17 pounds. I could feel a big difference both in acceleration and suspension control.

I agree with what has been said, for performance/looks yes, for efficiency no.

The stock wheels/tires are pretty heavy IMO and there is not yet any other 'mod' you can do to these cars to improve the performance.. I would think light wheels would sell for those reasons alone if somebody were to have a batch made up in 105mm. IMO the sweet spot would be a little cheaper&heavier than $800. Some good looking inexpensive cast 18 pounders should sell great.
I'll admit it. I'd like to change the wheels on my Bolt just because I don't like the looks of the stock wheel. I have no illusions of performance gains and since I'm usually a cheap *******, I fully intend to get all the mileage I paid for out of the stock tires as well as the range I paid for. When I get around to swapping wheels, the new wheels need to be able to use the stock tires.
 

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Im actually looking to go minus 1, 16x7, 5x105 offset 38 getting me to 13lbs.
If I were to get in on this, it would be for better handling and looks. Range is sufficient for my uses.

What I don't know (and am way too lazy to research) is what changing wheel size accomplishes.
Why would I want a wheel that the OEM tires don't fit on?
Are there more choices in non-OEM tires in the minus 1 size?
Do those tires offer better performance?

Thanks.
 

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My hunch is, that if there is an improvement, it is very subtle.
Exactly so.
One of the auto mags (Grassroots Motorsports) ran some tests a few years ago. Tested various wheel sizes, and concluded that the biggest measured acceleration difference was about .1 second to 60.
 

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Discussion Starter #25
Hey Bill,
It wouldn’t necessarily have to be the 16 we could go 17. The 16 is 13.7lbs and the 17 just under 15lbs. So performance wise the 16 would be optimal and pairing is a non issue. The guy from Enkei I spoke with took offset in consideration for the standard reasons scrub but also drag. We wanna keep that wheel in the wheel well. I’ll tell ya my research all started with an attempt to lower rolling weight and resistance during the winter months. I drive my bolt 150miles daily. Syracuse is atrocious in the winter so I’ll decided to buy hakkapalietta R2 205/60/16. If your not familiar its a premier Winter tire not to mention LRR. Easily 4lbs lighter than stock tire. I originally was gonna put them on steels, but decided decreasing rolling mass could only help. Short of it there’s nothing quality out there at this weight and price point. This is as blue collar as it gets for serious light wheel performance. outside of $1500 or greater forged wheel which may only get you a cpl lbs lighter. I guess in see this wheel as a nice extension of the pragmatic sexiness that is the bolt. Good chatting
 

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Initially I was going to use a top as my example of inertia, but as you point out, it does eventually come to rest. This is due to friction. A top spun in the vacuum of space would never cease to spin.

One thing I like to imagine is a bicycle on a perfectly smooth road on the moon, with an infinitely variable gear ratio. A person could pedal up to hundreds or even thousands of miles per hour on the moon if such a bike could be made with very low rolling resistance tires.

Back to the topic of wheel weight and how it has little to do with efficiency; weight does not affect aerodynamics at all (the biggest force to overcome, and by far the largest consumer of battery energy "range"), and almost nothing to do with rolling resistance (how much do those extra 44 lbs deform the tires compared to the 3,500 lb vehicle weight?). In other words, weight has next to nothing to do with frictional energy losses. Accelerating the weight of the wheels (rotational and linear) is the only other energy consideration, and it's a very minor one, especially on a vehicle capable of recapturing a good portion of the rotational and linear momentum.

We could put together some scenarios of different wheel weights and acceleration/deceleration events to calculate an approximate amount of energy saved by the lower weight wheels, but it would only confirm how vanishingly insignificant wheel weight is with regard to efficiency and range.
Friction. Both through air resistance and through the top's point of contact with the surface below. In space, with no resistance, the top would spin forever, and that would be true whether it was light as a feather or as heavy as an ocean liner.

The same is true of the wheels on a car. Once they're up to speed, their mass is irrelevant in terms of maintaining their angular momentum - the only thing that matters is bearing friction, air resistance, rolling resistance, and other frictional losses.

Now I suppose you can argue that on a rough surface where the suspension is being given a workout, the lower mass of the wheels might translate to a lower rolling resistance because the wheels would conform more easily to the undulating road surface. But even if that was true it would be pretty negligible compared to the other losses.
I think the comparison between the two points of reference might be the misunderstanding between us. The OP was asking the forum if anyone was interested in a wheel change here on earth, not on the moon. Even though it is not a statement I made before, it is possible for weight to affect aerodynamics in the way that when you consider the common materials used to make a car body, more weight usually means a larger body and more drag. As well, weight does affect frictional loss, just ask any truck driver about the energy cost of running a full load compared to an empty one. Same road, same truck/trailer dimensions with the same aerodynamic characteristics, different energy consumption. Load your Bolt with as much weight as you can get in it and see if it doesn't affect your range. Energy is required to keep an object moving here on earth because of the cumulative resistances encountered, of which weight is a factor. I don't see the relevance of redpoint5's comments about motion in the vacuum of space when the discussion was about motion here on earth. An increase in acceleration due to weight loss is not isolated to the decrease in weight alone. The energy cost due to frictional forces(resistance) of keeping a lighter object in motion is usually less then keeping a heavier object in motion. I think we would agree that the major energy loss with an ICE is in its transfer to the wheel contacting the road surface. Which is why a carbon fiber driveshaft can have such a positive effect on an ICE, it reduces energy transfer loss to the wheel. Practically speaking, take any form of road racing, and reducing the vehicle weight by 44lbs would be significant. To improve traction, racing cars use high friction contact tires. Add weight to that friction force and see what happens with energy consumption. With EV's, a greater portion of energy loss results from drag and rolling resistance(friction). My original point was that if the wheel change was capable of generating a noticeable improvement in acceleration, its also possible to offer an improvement in range as the car would be 44lbs lighter. Handling gains due to lower inertial mass are likely to be the most noticeable, but if low rolling resistance tires can add a 3% boost in fuel economy, how hard is it to believe that coupling that with wheels that weigh 44lbs less wouldn't add to that boost. But as I have already said, this is hard to say, and would have to be tested. One thing for sure is that it will not hurt your range. The enthusiast, and maybe that is the category I fall in, would try to find the best tire/wheel/aero cover combination possible, especially in the EV world where range and DCFC infrastructure seem to be questions of the day. I think we are mostly all here to make the Bolt, and maybe even EV's in general better. I think the OP offered a good suggestion toward that direction. Of course the cost of the upgrade will not appeal to everyone, even if it does yield a boost in fuel economy. But it might also translate into the convenience of having a few extra miles when you need it most, even if it does make driving the Bolt more fun.
 

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The OP was asking the forum if anyone was interested in a wheel change here on earth, not on the moon.
The laws of motion apply equally on earth, the moon, and in all the empty space in between- just as the rules for math apply regardless of location.

it is possible for weight to affect aerodynamics in the way that when you consider the common materials used to make a car body, more weight usually means a larger body and more drag.
For sure. Heavier objects are usually (but not always) larger. In this instance we are considering the shape of a wheel, which doesn't change very much with weight.

As well, weight does affect frictional loss, just ask any truck driver about the energy cost of running a full load compared to an empty one. Same road, same truck/trailer dimensions with the same aerodynamic characteristics, different energy consumption. Load your Bolt with as much weight as you can get in it and see if it doesn't affect your range.
Agreed, weight does affect frictional loss, but it's very, very small. We're talking about the minuscule energy lost due to the extra microscopic deformation of the steel bearings, and the extra deformation (flattening) of the tires due to that weight. When that extra weight is only 44lbs, these minute losses are not measurable.

Truckers traveling the same flat roads at the same constant speed (no braking) will observe little to no difference in fuel consumption full or empty when pulling their box trailers.

I don't own a Bolt, but I have observed no difference in fuel economy heavily loaded or empty on highway (constant speed) trips. In fact, it may be possible to get slightly better fuel economy in a fully loaded vehicle at constant speeds due to the compressed suspension and resulting lower ride height, which reduces frontal area.

... and to quote our physics experts of the internet :p, the truck drivers themselves:

2015 T680 76in
Mx-13 455 (possibly 485 the shop has been tinkering with it may have changed it)
13 speed

Bobtailing up to 9-11mpg @60-67 mph
Empty Trailer on flat terrain 8-9 mpg @ 62-66
on Hilly Terrain 7.8-8.6 @ 62-66
Loaded 60k On flat 7.8-8.8 @62-66
60k on hilly 7.4 -8.2 @62-66
This is a 2% loss in fuel economy adding about 40,000 lbs in weight.

2015 Prostar 73in
Cummins ISX450
10 SP Ultrashift+
Reefer

Hills/PA mountains at 19k: 7-8 mpg @68-70 MPH
Plains at 19k: 9 mpg @70 mph
Empty on flat lands: 9.4 [email protected] 60 mph
Here the guy shows 4% worse fuel economy hauling 19,000 lbs, but on second glance notice that he is also traveling 10 MPH slower empty, which would naturally account for better fuel economy.

"I drive 18 wheelers for a living and I have never seen a truck get much better than ~8 MPG. There does not seem to be a noticible difference loaded or empty in my experience."
"There shouldn't be. On a long haul at highway speeds, nearly all the power exerted goes to counteract air friction, which is dependent on the size and shape of the truck, not the weight."
Energy is required to keep an object moving here on earth because of the cumulative resistances encountered, of which weight is a factor.
Weight is not a direct factor with regards to resistances encountered. It indirectly affects friction due to deforming objects such as bearings and tires, but this is very minor.

The energy cost due to frictional forces(resistance) of keeping a lighter object in motion is usually less then keeping a heavier object in motion. I think we would agree that the major energy loss with an ICE is in its transfer to the wheel contacting the road surface. Which is why a carbon fiber driveshaft can have such a positive effect on an ICE, it reduces energy transfer loss to the wheel.
I may be misunderstanding what you are saying, but I would not agree that the major energy loss with an ICE is in transfer to the wheels. The primary loss of energy is heat going out the tailpipe, and through the radiator and engine. The conversion of the stored chemical energy of gasoline into engine power is only about 30% efficient, meaning about 70% is lost as heat. Of the remaining 30%, most of that is lost due to aerodynamic drag, followed by rolling resistance.

Carbon fiber driveshafts are used not to reduce frictional losses, but instead to reduce the weight of an object that takes considerable energy to spin up and which drastically changes RPM as it accelerates and decelerates. It's this constant changing speed that makes this an important area to reduce weight.

Practically speaking, take any form of road racing, and reducing the vehicle weight by 44lbs would be significant.
Agreed, but racing is not similar to commuting (for most people), and it's a sport where hundredths of a second matter. Speed is constantly changing and the brakes are used very frequently and at maximum capabilities. If the race was on a straight road across America, the weight would hardly matter.

My original point was that if the wheel change was capable of generating a noticeable improvement in acceleration, its also possible to offer an improvement in range as the car would be 44lbs lighter.
Also agreed. That increase in range would be imperceptible for most people unless they were racing their vehicle. I haven't done any math, but my guesstimate is the typical driver would see a few tenths of a mile more range, which would likely be more than offset by the less aerodynamic design of the wheel. The spokes would chop at the air more, rather than cleanly slice through.

Handling gains due to lower inertial mass are likely to be the most noticeable, but if low rolling resistance tires can add a 3% boost in fuel economy, how hard is it to believe that coupling that with wheels that weigh 44lbs less wouldn't add to that boost.
Bending the rubber in a tire so that it smashes into a flat contact patch on the asphalt takes considerable energy. Take a rubber-band and rapidly stretch and compress it for a while and notice the heat generated. That's wasted energy. The 4 tires are all undergoing this stretch / relax process and resisting the change in shape, which is why engineering them to not heat up so much while being deformed can save significant energy. If the wheels could be made of steel like a train, there would be drastically less rolling resistance, but also drastically less traction and a drastically harsher ride.

One thing for sure is that it will not hurt your range.
For sure (concerning weight). My only point is that it would be unreasonable to expect a 5 mile improvement in range, especially given the more likely probability of slightly less range due to poor aerodynamic design. From the EPA: "An extra 100 pounds in your vehicle could reduce your MPG by about 1%"

...it might also translate into the convenience of having a few extra miles when you need it most, even if it does make driving the Bolt more fun.
It's more probable that range would be slightly decreased due to aerodynamic drag unless wheel covers were added. The gains in range would likely be measured in tenths of a mile. In other words, range can be improved more easily by adding wheel covers to the stock Bolt wheels, than by reducing wheel weight alone.

Buy lightweight wheels to improve handling characteristics and quarter mile drag times, but don't expect to see any range improvement.
 

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http://www.motegiracing.com/wheel/23456/mr131-traklite/

Street price on these 17x7 wheels is $110 and they are 18 pounds. This is the sweet spot I think market wise. If you could drill up something @ 15 pounds and sell for double that price, that could work too, but you would be limiting your customer base with that step up. Personally I'd prefer 15x7 or 16" over the 17" size, but I'm sure we are the minority.
 

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We could put together some scenarios of different wheel weights and acceleration/deceleration events to calculate an approximate amount of energy saved by the lower weight wheels, but it would only confirm how vanishingly insignificant wheel weight is with regard to efficiency and range.
Hmm...my ideal weight is about 40lbs below current. How about I go on a diet and see how things change?
 

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Rotational mass weight saving is equal to twice that of static weight. So if you lose 12 lbs per corner, it would be 48 lbs for the set in rotational mass. So it would actually be like saving 96 lbs in static weight. You will feel the difference in suspension control, handling, acceleration, braking. It might help efficiency a bit in city driving . How much? Each car model is different so it would have to be tested. On the highway it makes no difference. Aero makes a bigger difference and putting full covers on the wheels should reduce overall consumptions around 5% easily.


I installed 17x8 fastwheels fc04 on my Volt which are 5 lbs less than stock wheels and I can feel the difference in how the suspension handles bumps, etc... Much better. I've lost about 7% when the tires were new , but after about 4000km on the tires the range came back to where it was pretty much. I installed Conti DWS 06. Very good balanced tire.


People who want to lose weight and keep the stock tires you can fit them to the FC04. 215mm is pretty much the same width of the wheel. I have 215mm on my car and it is not stretched. FC04 in 17x8 weigh 16.2 lbs so it is pretty lightweight and is not expensive. I think in the US they go for around 130$ each. Pretty cheap for a flow formed 17inch wheel. They also come in 5x105mm.


Here are pics of Fc04 on a Bolt with stock tire size.
 

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Discussion Starter #35
Hi Hatchy,
For clarity im not selling anything. I just wanted access to factory drilled 5x105 ENKEI RPF1's on my bolt. In order for ENKEI to do that they request 5sets ordered, and then would coordinate with OAKOS.com. All communication is btwn whomever is interested and [email protected]. Im just trying get this going so fellow bolt drivers will access to this classic ultra light wheel. The 16 which they will Factory Drilled for us would be a 16x7 5x105 ET43 @13.7lbs or 17x7, [email protected]. Im willing to go either way just up to what 4other people would prefer.
I actually looked at that motegis you end stuck with the mr116 since the mr131 doesn't come in 5x105. The MR116 is 19lbs @17inch. No [email protected] 5X105. You just cant compare the RPF1 its legendary in comparison. Hopefully we be able to make it happen. It will be a fun day to clock thee old girl. Cheers!
 

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Discussion Starter #36
Hey EVOLT,
Yeah the fellas at Fast Wheels are nice. Its a decent light wheel and TUV certified I believe. I actually almost bought it but didn't like the 8inch width. Glad you enjoy. AWSIDE has good pricing on them. Defn one of few decent lightwheel choices.
 

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GRM did a miata test where the lighter wheels dropped 0.43 seconds from the 0-60 time. That jives with timetoy's results. 6 second to 60mph is wonderful. Puts a Bolt right up there in some great company.

https://grassrootsmotorsports.com/articles/are-lighter-wheels-really-better/

Hi Hatchy,
For clarity im not selling anything. I just wanted access to factory drilled 5x105 ENKEI RPF1's on my bolt. In order for ENKEI to do that they request 5sets ordered, and then would coordinate with OAKOS.com. All communication is btwn whomever is interested and [email protected]. Im just trying get this going so fellow bolt drivers will access to this classic ultra light wheel. The 16 which they will Factory Drilled for us would be a 16x7 5x105 ET43 @13.7lbs or 17x7, [email protected] Im willing to go either way just up to what 4other people would prefer.
I actually looked at that motegis you end stuck with the mr116 since the mr131 doesn't come in 5x105. The MR116 is 19lbs @17inch. No [email protected] 5X105. You just cant compare the RPF1 its legendary in comparison. Hopefully we be able to make it happen. It will be a fun day to clock thee old girl. Cheers!
Gotcha. Right def would prefer the lighter 16 if it were my money. Inertia wise even a 15 pound 16 would out perform a 15 pound 17.. you've got to remember hardly any mass in the face of the wheel. Smaller wheels move a lot of mass towards the center of rotation which is a good thing.
 

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Aero makes a bigger difference and putting full covers on the wheels should reduce overall consumptions around 5% easily.
I'd bet serious money against that assertion. If there were 5% range increase in full wheel covers, no EV would ever be sold without them.

jack vines
 

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I'd bet serious money against that assertion. If there were 5% range increase in full wheel covers, no EV would ever be sold without them.

jack vines
Well, marketing is also important. All engineering is a compromise and trade offs. Generally, public consensus is, wheel covers are hideous and ugly. Spindly, spidery looking wheels like those pictured in this thread are vogue. Manufacturers know all too well that "curb appeal" matters if you want to make the sale.

Having said all that, I'm surprised that manufacturers haven't offered wheels that accept aero wheel covers as an extra cost option. Even if they only worked to extend range the tiniest bit, some people would pay extra to get them.
 

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...Again, once they are up to speed, no further energy is required ever again...
Hey redpoint5 great post. You, DaV8or, and others here are right, I may be over-projecting the effect of weight on resistance. But I don't normally think of fuel economy here on earth using space travel as the example. It puts things in a loop, but admittedly I get that a lot from discussions with you. It is at times hard to figure out which direction you are going, and sometimes it appears that you have more than one at the same time. Your statement quoted above is not true, and does not apply to moving objects on earth. Energy must be continually expended if you expect to remain in motion. You can coast for a while, but will ultimately need an energy input unless you plan on stopping. I think the flat drive, put your tranny in neutral example was pretty self explanatory. So no, energy will be required again, and again, and again... as long as you expect to keep moving, or unless you are on the moon.

...Heavier objects are usually (but not always) larger. In this instance we are considering the shape of a wheel, which doesn't change very much with weight...


...The primary loss of energy is heat going out the tailpipe, and through the radiator and engine. The conversion of the stored chemical energy of gasoline into engine power is only about 30% efficient, meaning about 70% is lost as heat. Of the remaining 30%, most of that is lost due to aerodynamic drag, followed by rolling resistance.
Regarding aerodynamics, no I wasn't considering the shape of the wheel. You brought up aerodynamics. Aerodynamics was never part of my consideration concerning wheel weight. I was discussing the effects of total weight reduction related to resistance at steady speed. This is just another of the many directions you seem to take in a single discussion, so I was trying to answer to your comment that weight has no relationship with aerodynamics. There is in fact a strong relationship between aerodynamics and the size of a cars body/weight. So I would maintain that weight does affect aerodynamics of a car as it relates to size.

Regarding energy loss, my bad, I maybe should have used "POWER" to make it more readable for you. If we were on the moon, gas exhaust from the tail pipe might have an effect, but I was trying to get at a cars motion here on earth. Skipping over all the in between, the loss in power between the flywheel and the drive-wheel is reduced with a lighter weight drive-shaft. And, I never gave an estimate as to possible gains. If you go back and read my posts, I tipped my hat to you for doing that exact thing. I said that it would be hard to tell and that I would add aero wheels to maximize the gain.

You point about loading weight and fuel economy is a good one. It seems reasonable that modding the suspension to lower the car would help maximize the benefit of lighter wheels, since drag effects count so much more with EV's. I think the take-away for me if the object was to maximize cornering ability, acceleration, and range would be to use lighter wheels, least resistance-best grip tires, aero-wheels along with lowering the suspension.
 
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