## Gen II light weight wheels and tires

DaveinOlyWA
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### Re: Gen II light weight wheels and tires

watchdoc wrote: Fri Jan 14, 2022 11:45 am
DaveinOlyWA wrote: Fri Jan 14, 2022 9:22 am We are not looking at "unsprung weight" We need a rotational mass calculation to quantify the difference. An 8 lb difference is significant. The wheel size to efficiency effect I first discovered while perusing the 2010 Prius during its reveal at the 2009 Detroit Auto show. While looking the car over, we found the engineer's notebook in the car and started thumbing thru it. As you would expect; most of it was unreadable but the page stating a the mpg differences between tire sizes was unmistakable.

F = m*v^2/r
Summarize your point for me please. So you're saying skinnier tires has more effect than unsprung weight?

The combo I'm looking at would be greater than 10lbs per corner lighter but retain the stock 215 tire size.

This article seems to indicate that tire width is much less important than rolling resistance and wheel size.

https://www.greencarreports.com/news/11 ... icle-range

So here's my question. assuming everything else is the same (same tire, same width, same total diameter, same total weight) would a 16" wheel and tire combo be more efficient than a 17" wheel and tire combo? If so, why???
Question; its the weight. smaller wheel diameter simply means taller tire so overall diameter would be the same or very close to it. The reality is driving on low profile tires is well... I don't know. I don't know why people think they are cooler, look better or anything else for that matter.

The shorter sidewall means less flex so more beefing to be able to handle the degrading American infrastructure.

Looking at the formula and determine what changes. In your question, only the mass changes. If the wheel size actually did control the diameter, then yeah, efficiency would skyrocket but the difference is pretty small but a 25% difference in weight is significant.

As far as the article, its right only in that more efficiency is not a one shot deal. Its a lot of stuff; LRR tires, max safe tire pressure, smaller wheels which are almost always lighter than tires unless you get the super expensive alloys which I know some that have and they don't seem to hold up well over time but never really got many details on it simply because it wasn't possible to get a favorable ROI.

You want efficiency; use constant power, minimize sprints and regen and never use braking if possible. Now all that is a challenge but every second you make it is a bump on the range and also good for the battery as well. We all want the gentle life and your pack is no different.
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 25,047 mi, 92.12% SOH
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knightmb
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### Re: Gen II light weight wheels and tires

Skinny tires do have slightly less air resistance, but the energy savings is very small. Lighter wheels have less rotational energy, thus less energy to drive them *and* steer them. Basically you are replacing metal with air on smaller rims and bigger tires. The weight savings adds up over the long run and saves energy, which for an electric vehicle can be a lot of miles. Bigger tires also means less chance of damaging the rim in a deep pothole and better shock absorption for a smooth ride.
On a Tesla Model 3 for example, just changing from 20" rims to 18" rims (same wheel diameter while traveling at 75 mph) gains you 39 miles in range. It's no magic, just lighter wheels that take less energy to drive.
watchdoc wrote: Fri Jan 14, 2022 11:45 am
DaveinOlyWA wrote: Fri Jan 14, 2022 9:22 am We are not looking at "unsprung weight" We need a rotational mass calculation to quantify the difference. An 8 lb difference is significant. The wheel size to efficiency effect I first discovered while perusing the 2010 Prius during its reveal at the 2009 Detroit Auto show. While looking the car over, we found the engineer's notebook in the car and started thumbing thru it. As you would expect; most of it was unreadable but the page stating a the mpg differences between tire sizes was unmistakable.

F = m*v^2/r
Summarize your point for me please. So you're saying skinnier tires has more effect than unsprung weight?

The combo I'm looking at would be greater than 10lbs per corner lighter but retain the stock 215 tire size.

This article seems to indicate that tire width is much less important than rolling resistance and wheel size.

https://www.greencarreports.com/news/11 ... icle-range

So here's my question. assuming everything else is the same (same tire, same width, same total diameter, same total weight) would a 16" wheel and tire combo be more efficient than a 17" wheel and tire combo? If so, why???
2020 Leaf SL Plus - (Manufacture Date March 2020)
2018 Leaf SL - (Manufacture Date February 2018)
2013 Leaf SV - (8 faithful years of service before trade in at 75,679 miles LeafSpy-Data)
Timekoin - The World's Most Energy Efficient Encrypted Digital Currency
DougWantsALeaf
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### Re: Gen II light weight wheels and tires

Smaller wheels also tend to move more mass to the center of the wheel and away from the edge, which is more efficient.
2019 S Plus (93.1% SOH) & 2019 SV Plus (90.7% SOH) Both Silver
2013 Leaf SV sold 2019 with 11 bars
100 Mile Club Member (Number 87)
Max Miles on 13 Leaf: 120 miles
Max Miles on 19 SV+: 242 Highway miles @ 4.5 miles/kWh
sreidvt
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Joined: Mon Nov 22, 2021 12:03 pm
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### Re: Gen II light weight wheels and tires

HerdingElectrons wrote: Wed Jan 12, 2022 10:36 am
The wheels are 16x7 and supposedly weigh 18.92# each. I ended up using Ecopia 422+ tires and the combined weight measured by me holding the mounted combo on my personal scale & then weighing myself was 39.8#'s

Last March I paid \$965 before tax for the wheel/tire combo.

http://www.veloxwheels.com/wheels/mantra
38mm offset and IIRC 114.3 bolt pattern

I typically see a 3-10% improvement in consumption & the car felt more lively under initial acceleration.
Where did you order that tire combination from? Thanks.
HerdingElectrons
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### Re: Gen II light weight wheels and tires

sreidvt wrote: Sat Jan 22, 2022 12:21 pm
HerdingElectrons wrote: Wed Jan 12, 2022 10:36 am
The wheels are 16x7 and supposedly weigh 18.92# each. I ended up using Ecopia 422+ tires and the combined weight measured by me holding the mounted combo on my personal scale & then weighing myself was 39.8#'s

Last March I paid \$965 before tax for the wheel/tire combo.

http://www.veloxwheels.com/wheels/mantra
38mm offset and IIRC 114.3 bolt pattern

I typically see a 3-10% improvement in consumption & the car felt more lively under initial acceleration.
Where did you order that tire combination from? Thanks.
Costco Tire Center & I edited the original post I made to reflect that.
2018 SL Pearl White 4.5/3.9; 5.0/4.6 with 205/65/16 tires)

09/18-01K Mi: 114.52AHr / SOH= 99.20%
04/19-10K Mi: 111.45AHr / SOH= 96.54%
11/19-20K Mi: 107.44AHr / SOH= 93.07%
12/20-33K Mi: 105.39Ahr / SOH= 91.29%
04/21-35K Mi: 104.32Ahr / SOH= 90.37%
Ital74
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### Re: Gen II light weight wheels and tires

I am thinking the same. Basically keeping same tire size and just getting lighter rims with better offset for a wider flush stance. I've been using on tire rack a 2003 nissan 300z for some low et wheels.
I think 17x8 et 35 is what I would want
I found cheap ones around \$150 each. I might give it a try... anyway i don't think it can make it worse.

Thanks
Ital74
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Location: Connecticut

### Re: Gen II light weight wheels and tires

Found a very interesting article that pretty much states that lighter wheels really do not affect range noticeably.

https://allev.info/2020/03/does-wheel-weight-matter/
GerryAZ
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### Re: Gen II light weight wheels and tires

I am on the second set of replacement tires with my 2019 (OEM 17-inch alloy wheels). The OEM Michelins were the lightest weight and smallest size at 215/50 R17. The first replacements were Bridgestone DriveGuard run flat capable tires that were one size larger at 215/55 R17. They were by far the heaviest and had a noticeable negative impact on acceleration. There was a small reduction in range (efficiency) at highway speeds after a few thousand miles break in, but a larger reduction in efficiency during stop/go driving due to the increased rotational mass.

I am really happy with the current tires which are Michelin Cross Climate 2's in the same size as the DriveGuards at 215/55 R17. Their weight is higher than the OEM Michelins, but significantly lower than the DriveGuards. Acceleration returned to normal with the Cross Climate 2's even though they are larger diameter than the OEM Michelins. Efficiency is better than with the DriveGuards, especially during stop/go driving.

I prefer the slightly larger 215/55 R17 size and plan to stay with the Cross Climate 2's unless something happens to change my mind. My experience convinces me that the main impact of rotating mass reduction is to improve acceleration and efficiency during stop/go driving. There is very little benefit to efficiency at constant speed such as during highway driving. This is consistent with results noted in the linked article.
Gerry
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Ital74
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### Re: Gen II light weight wheels and tires

I too am considering larger tires but 225/50R17
DaveinOlyWA
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### Re: Gen II light weight wheels and tires

rlmalisz wrote: Wed Jan 12, 2022 8:22 am FWIW, I did a longish "ugly weather" test drive i my S+ a month or so back. What I found with the S+ was that the speedometer over-reported speed by about 5%, and that the odometer over-reported distance by 3%. This was just over 120 miles each direction, results were consistent both ways. Pouring rain, nasty winds, about 40F outside, 70mph (ambient traffic speed was probably 75+)...so efficiency was nothing to write home about. But distance is distance, and this was nearly all freeway, straight-line driving. I assumed this was because Nissan calibrated the odo/speedo for the larger rim/tire combo, and didn't bother to change anything for the 16" setups.

Anyway, when I calculate M/kWh, I am reducing the reported values by multiplying them by 0.97. Not a big deal. But may be a factor in your numbers. You say the SV+ under-reported distance. Might be worth taking a longer spin in one vehicle or the other (or both) to double-check.

--Richard

PS: Really wish this was a correction that could be made without changing tire sizes!
How did you check your odometer? I haven't looked at the Plus but my 2013 and 2016 (both S both 16" Ecopias) were pretty close when using Google maps for a guide. I also tried 3 different GPS apps to check speedo and all gave the same results but expected as Speedo tend to brag about speed anyway but didn't see a 3 mph difference until I hit 70. In all cases, the app only provided whole mph readings so don't know if 70 was a true 3 mph differences or simply 2.51 mph?
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 25,047 mi, 92.12% SOH
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;