How tire pressure impacts range - insight into impact of 245/50 R19 tires on stock 19 wheels?

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mkhuffman

mkhuffman

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Here is my follow up note I installed a set of Vredestein Hypertrac 245/50/19 104V tires on a aftermarket set of rims. Rims are 19x8.5 +20 offset.i have noticed very little to no impact on range on the highway. The load range is so close to factory 225/55/19 103h I just left the pressure the same. My wheel / tire combo is 6lbs lighter than factory and this seems to make the car feel like it accelerates faster and positively impacts range around town.i think aerodynamics is negatively affecting my highway performance but it's almost counteracted by the weight being less hence no noticeable difference in range
The weight difference should not have an impact on highway range. The only significant factors are rolling resistance and aerodynamics when driving at a steady speed. Weight will have an impact when accelerating, but less so when slowing down, since you can use regen breaking to capture some of that extra inertia from heavier wheels.
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I found this article that tested the impact of tire pressure on BEV range.

https://www.sae.org/news/2020/10/tire-pressure-impact-on-ev-driving-range

I am trying to determine if I want to change out the tires with 245/50 R19 tires to give the car a more aggressive look, and to improve handling. But I do not want to significantly impact highway range. It seems to me that adding width may be similar to low tie pressure, and maybe increasing tire pressure before a highway trip could offset the impact of getting wider tires.

According to the article, proper (and high) air pressure in the tires can improve range:
"Over the vehicle’s life, a variable tire RRC could account for up to 4% battery-charge difference. Reducing IPLR and “in-use” RRC creates the potential for Tier-1 suppliers and OEMs to consider a lighter and/or less-expensive battery. And ExxonMobil Chemical road testing has demonstrated that EV range can be improved from 3-7% with optimized tire IPLR. "

It seems a 5% hit to range is possible due to the wider and stickier tires. However, I bet if you crank up the air pressure in the tires, that can be mitigated significantly. My guess is with 32 psi, you probably will see close to a 5% range hit with the wider tires. I guess that raising the pressure to 40 will reduce that impact, so a good guestimate is 2-3%. I will go with 3% for a worst case analysis. 210 miles of highway range (on a full charge) will become 204 miles. So I guess you will loose 6 miles of range with 245 tires. If that is true, it is worth it to me to replace the tires. I hope someone will test this. Or maybe I will...

On a side note, it is interesting how significantly tire pressure impacts range. I bet a lot of EV owners do not monitor tire pressure and are getting less range just because their tire pressure is low.
Good post and tire pressure impact on range is not new or isolated to only EV's. Force of friction is weight x a coefficient of friction (varies). When your tires are low that coefficient may increase but should be independent of contact area. Force of friction is only dependent on normal weight and not contact area. The lose I think is also dependent on the power required to spin the larger heavier wheel. Something about the mass moment of inertia?

Someone bought larger tires on the forum as they felt the stock did not make them feel safe. Maybe tracking them down and a PM may help. If you can not locate them PM me maybe I can.
 

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The weight difference should not have an impact on highway range. The only significant factors are rolling resistance and aerodynamics when driving at a steady speed. Weight will have an impact when accelerating, but less so when slowing down, since you can use regen breaking to capture some of that extra inertia from heavier wheels.
I think this is both correct and not, everything is affected by weight. That being said it may not be very much and in most cases not worth spending a ton of money to get a set of uber lightweight wheels. I would consider it something to look at if you are buying aftermarket wheels.

The biggest place you would notice wheel weight reduction is handling/cornering and acceleration. My winter wheel tire combo is 13lbs per wheel less than the factory or 52lbs less total I bet it will make a difference you can feel

I have attached an article from TR where they test both heavy and lightweight wheels with the same tire and they do find a MPG benefit.

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=108

The bigger improvement was in the factory low rolling resistance tire about 6%, the lightweight wheel is about a 2% increase in MPG. imagine

This is my point the lighter weight wheels seem to make up for the inefficiency of the wider tire in my case. I expect the even lighter winter combo should do better yet.
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