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Discussion Starter · #1 ·
Hey folks, bolt owner here in Syracuse ny and couldn't be happier! I read some early posts on decreasing wheel weight and feel this should be a much hotter topic. Seeing as decreasing unsprung weight is one of the most important efficiency mods we can make. For the last cpl months I have been researching light-weight wheel options. As many of you know they are far and few in the 5x105 bolt pattern. I initiated the standard search of tirerack and discount tire direct which had limited lightweight options. I personally felt forged wheels were cost prohibitive. MotegiMR116 and EnkeiEV5 are in the 19lb range at 17inch. Fast wheels out of Canada makes a nice 16lb FCO4 17x8 wheel but I wanted to keep my stock tires. I then found a bunch of sites in Europe which opened up a lot of styles but limited weight reduction. There is a good wheel out of Europe called " team dynamics pro race 1.2" and it comes in at 16lbs. Massively improved from the oem 24lb wheel. I kept making phone calls and ran across Oakos.com. These guys specifically, nick were interested in tackling this challenge. He actually carries the team dynamics pro race 1.2, but more interesting they do a great deal of business with Enkei. He brought up the famously light Enkei RPF1, which depending on wheel size can get you in the 13lb range! Nick from Oakos said he has close contact to Enkei and could have blanks drilled to 5x105. If 5 or more fellow bolters contact him with interest he said he could make order. I would love to see this option open for all of us. Im actually looking to go minus 1, 16x7, 5x105 offset 38 getting me to 13lbs. I will get nicks email/phone for those who are interested in creating this avenue. Look forward to getting something started!
 

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Nick from Oakos said he has close contact to Enkei and could have blanks drilled to 5x105. If 5 or more fellow bolters contact him with interest he said he could make order.


Enkei RPF1 (17x8)

Drilling 5x105 or any other bolt pattern using blanks isn't really rocket science. Every other fitment shop around does it. These are $225 wheels (you didn't mention price). Cost $40 to drill any pattern at most shops, and if one buys a decent set, typically the drilling is done for free. If they can sell 20 Enkei blanks, why can't they sell you 4?

Perhaps this post is better positioned in Chevy Bolt EV Parts And Accessories For Sale?
 

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Wheel weight has little to do with efficiency, especially on a vehicle that recaptures a good portion of that rotational energy when decelerating. That said, reducing wheel weight is a good way to improve acceleration and handling. With regard to acceleration; it's not just the weight that is a concern, but also where the weight is located. Reducing weight toward the center of the wheel will have little impact on acceleration, but reducing weight further out towards the tire will have a greater impact, which brings up the topic of lighter weight tires.

Good topic though, and I'm surprised I haven't seen a general weight reduction thread for this car yet.
 

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Discussion Starter · #4 ·
Shotel,
That was my introduction post. I will move it to accessories. I agree drilling is not rocket science. Try calling Enkei for 4 blank 17inchx7 wheels. You need to be doing business with them. Oakos is not the only outfit that could do this but they are open to accommodating a niche to Bolters to cut weight. Of course its in there interest but that's capitalism. We would have these wheels drilled direct from Enkei, oakos would not be drilling or redrilling. Its essentially a point of contact to get the blanks, ie wheels made. Futhermore, if you to try searching blanks for the the Enkei RPF1 17x7 you wont find anything. Ive seen no where on this blog or the internet where you can capture a 13ish pound wheel. Your right this is not a expensive wheel. Hence why I found it to be the best lightweight option. Of course its also a classic durable wheel. Your next option is forged which is gonna be minimum $1500 a wheel. Hi redpoint, so I would like to combine this with a lower weight LRR wheel. So hoping to decrease my unsprung wheel weight by about 13lbs a corner wheels and tires. Fun stuff, cheers!
 

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I think if you want to improve performance of your Bolt, it's not a bad idea. A 44lb reduction in total wheel weight is a very decent savings. Racers upgrading to a carbon fibre driveshaft shave off about half that weight to gain a couple tenths in the quarter-mile. More importantly to the EV user, I can't see why it wouldn't improve range too. If less power needed to move the car means better acceleration, then it should also translate to increased range. If lighter weight wheels decrease the regen of an EV, it is only because the car will stop a little quicker.

I would be with you if I already had my Bolt.
 

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Or you could settle for the 17lb. Cruze Eco wheel, which is forged, IIRC.
I think some here have used this wheel. Can anyone tell is they saw any measurable difference in some sort of performance metric? My hunch is, that if there is an improvement, it is very subtle.
 

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More importantly to the EV user, I can't see why it wouldn't improve range too. If less power needed to move the car means better acceleration, then it should also translate to increased range. If lighter weight wheels decrease the regen of an EV, it is only because the car will stop a little quicker.
Reducing rotational energy (lighter wheels) will improve range, but the impact is so small as to not be noticable / measurable. The only time rotational energy is wasted is when regen or braking occurs, and the Bolt recaptures a good portion of that energy. Most energy is spent overcoming aerodynamic drag, followed by rolling resistance. The amount of energy spent accelerating wheels up to speed is proportionally much smaller since aero and rolling drag is more constant, while braking (should) only accounts for a small amount of driving.

Lighter wheels will spin up to speed faster, and with less energy required. They therefore slightly reduce the amount of recaptured energy during regen braking since less energy was required to get them up to speed in the first place. This should result in slightly faster deceleration under full regen conditions.

As I say, performance and handling will noticeably improve, but efficiency will be imperceptible. Just the fact that the wheels aren't built with aerodynamics as a top priority will likely more than offset any efficiency gains. I like the idea of lighter wheels, but people should not be under the impression they will get several more miles of range.
 

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...The amount of energy spent accelerating wheels up to speed is proportionally much smaller since aero and rolling drag is more constant...

Lighter wheels will spin up to speed faster, and with less energy required. They therefore slightly reduce the amount of recaptured energy during regen braking since less energy was required to get them up to speed in the first place...

...I like the idea of lighter wheels, but people should not be under the impression they will get several more miles of range.
Hey redpoint5. I get part of what you are saying, you can't recapture energy you have not spent, which should translate into a range increase. I wonder if the point being missed is that the decreased energy expenditure is not only experienced during acceleration, but is also present at steady speed as the amount of energy needed to maintain any given speed is reduced. So the decrease in energy consumption therefore becomes in part a function of time (mph). Whether a 44lb reduction in total wheel weight can translate into a noticeable gain in range for the Bolt would have to be tested. It may be that the energy needed to overcome the drag effect of its frontal area and body shape is high enough that it will obscure any net gain from reduced wheel weight, but I would like to think that it should still show some difference, and would make a good starting point for anyone interested in eking out as much performance from their Bolt as possible. What I would add to the OP's suggestion, which IMO were decent looking rims, would be an aero wheel cover. I have heard of as much as a 10% gain in range with other EV models. Devising a clear plastic vented cover that can show-off the sexy rims behind shouldn't be that big of a stretch. And a 10%+ gain in range for the Bolt would be a roll in the right direction.
 

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...the decreased energy expenditure is not only experienced during acceleration, but is also present at steady speed as the amount of energy needed to maintain any given speed is reduced. So the decrease in energy consumption therefore becomes in part a function of time (mph). Whether a 44lb reduction in total wheel weight can translate into a noticeable gain in range for the Bolt would have to be tested. It may be that the energy needed to overcome the drag effect of its frontal area and body shape is high enough that it will obscure any net gain from reduced wheel weight, but I would like to think that it should still show some difference, and would make a good starting point for anyone interested in eking out as much performance from their Bolt as possible. What I would add to the OP's suggestion, which IMO were decent looking rims, would be an aero wheel cover. I have heard of as much as a 10% gain in range with other EV models. Devising a clear plastic vented cover that can show-off the sexy rims behind shouldn't be that big of a stretch. And a 10%+ gain in range for the Bolt would be a roll in the right direction.
As you likely know Joule, but for the sake of clarity to the larger audience, momentum and rotational energy are preserved indefinitely. That is to say, an object in motion stays in motion, so once the energy is expended to bring something up to speed, such as the wheel rotation, or the vehicles overall speed, no further energy expenditure is needed. At that point, the only energy expenditure required is that to overcome drag (or that to overcome gravity if going uphill). To visualize this concept, consider that no energy is required to keep the earth spinning on its axis, or to rotate around the sun for millions of years.

The biggest energy cost with regards to wheel weight is spinning them up to speed. There is a secondary cost, which is the energy required to accelerate the weight of the wheels up to vehicle speed (rotational acceleration vs linear acceleration). Again, once they are up to speed, no further energy is required ever again, unless they are slowed down with braking and are required to be accelerated again.

It does take energy to move vehicle weight (including the weight of wheels) up a hill, but this energy is returned when going back down. If the hill is too steep, you might have to use regen to bleed off some speed, but that energy is largely recaptured.

As you point out, improving the aerodynamics of the wheel has much more impact on efficiency than weight. From what I've read, I expect wheel covers to give a 1-3% efficiency improvement, which is within the range of "noise" the average person would experience if attempting to test the modification. I'd expect the range improvement from reduced weight to be less than 1% under typical driving conditions, which would make measuring the effect extremely difficult.

Those interested in improving range should start with driving slower, followed by increasing tire pressure, followed by avoiding brakes/regen as much as possible, followed by aerodynamic improvements, and lastly, weight reduction.
 

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Shotel,
That was my introduction post.
I didn't mean to offend in any sense, however a new members first post that seems to be selling something was cause for my response.

I guess I am missing the point of attempting to get more efficiency from a 238 Mile range EV. It's not like the Bolt is a Gen1 Leaf or Spark. If, as redpoint5 suggest,; "driving slower, followed by increasing tire pressure, followed by avoiding brakes/regen as much as possible, followed by aerodynamic improvements..." are best first step practices to increased efficiency, all of which are free except any aero improvements, what is the justification for spending $800+ for wheels in terms of ROI?

I may spend $1,000 on 18" wheels + performance tires for far improved handling, but that expense would only go to my driving enjoyment. I may indeed get less range with this kit, but for my driving habits it will work. Help me understand the need and expense for such a seemingly minor efficiency increase.
 

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First of all, thanks for your efforts in researching lighter wheels. I'd like a set of lighter wheels for lighter summer tires and then use the OEM wheels for winter tires. Reducing unsprung weight by 10-15# per corner has a significant improvement in ride and handling.

I guess I am missing the point of attempting to get more efficiency from a 238 Mile range EV.
For true, you're totally missing the point. As has been patiently explained by those who understand how and why, lighter wheels add very little measurable range efficiency to an EV.

jack vines
 

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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.
 

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It does take energy to move vehicle weight (including the weight of wheels) up a hill, but this energy is returned when going back down...
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? For the sake of this discussion, I might even more appropriately ask why when we drive a car(bike) over a completely flat surface, EV, pedal or otherwise, do we have to continually apply power in order for the car(bike) to stay in motion? I will give you a hint, resistance. If you have never experienced this, just take your car or bike for a drive over a completely flat stretch of road, or dried out lake bed, and once you are at your desired speed, take your hand or foot off the accelerator and place the transmission in neutral. I am hoping you will notice a gradual slow down in your speed, and I am guessing that you should eventually stop without braking, no hill required. Unless of course there is an object in your path, then I would encourage you to brake. From you explanation, I get the impression that you think the wheels are part of the car, but somehow a separate entity at the same time, and that the amount of energy needed to make them move is somehow isolated to the wheels alone. Even if this were true, the resistance encountered at the connecting point between the chassis and wheel (bearing) would require a constant power to overcome this resistance in order for motion to continue. But the wheel is not an object unto itself. It has a mass, which is a part of the cars total mass. You mention momentum and weight, so I get the feeling that you are half-way to another part of this story. Inertia. But enough of that, I couldn't even begin to guess at a percent increase in efficiency so hats off to you. But I expect the number would vary between cars depending on differences in resistance around the wheel well of each car. The more resistance in that area, the greater the chance that you have at recuperating efficiency by streamlining it. Just my 44lbs worth.
 

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Discussion Starter · #18 ·
Great talk guys. Not a fan of the Chevy Cruze option forged option because of look or weight, but thanks for thought. This is certainly a multifactorial situation with weight being a player. How much is the question. It would be nice to have metric feedback. How one drives further complicates things. Quite frankly, this blog has been soft on extended range modifications. So it’s nice to have this dialogue. I plan on moving forward with the addition of wheel cover augments and lower weight LRR tires. At minimum there will be mild improvement plus, drive quality, acceleration and look. Where talkin potential 14lbs off each corner. Those interested fire me a message. I actually spoke with Enkei today and they willbe sending me optimal parameters at 16 or 17 inch diameter. [email protected] is his email. Chris highly recommend coordinating with the previously mentioned outfit at Oakes.com. The previously coordinated custom Enkei orders for other groups. Those interested can email [email protected]. We’ve talked so he is ready and expecting to answer questions. We would need 10-orders for Enkei to proceed with custom order of the RPF1.
Unrelated, just had my car ceramic pro coated, and highly recommend!
 

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Discussion Starter · #19 ·
Shotel,
I don't want to give this much attention since the dialogue has been so great. The title of my post was CO-OP, co-operative. I actually cant answer why anyone wouldn't want more efficiency and performance. To each there own, of course. Your ROI is enjoyment,. Cars are not an investment. This is supposed to be fun.
Cheers nonetheless!
 

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...why a spinning top will eventually come to rest? For the sake of this discussion, I might even more appropriately ask why when we drive a car(bike) over a completely flat surface, EV, pedal or otherwise, do we have to continually apply power in order for the car(bike) to stay in motion? I will give you a hint, resistance. ...the resistance encountered at the connecting point between the chassis and wheel (bearing) would require a constant power to overcome this resistance in order for motion to continue.
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.
 
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