50% of your EV energy consumption comes from wheels and tires

[Vekke]

I have been cracking some numbers related to my new wheels and tires and it seems that 50% of your electric cars energy consumption comes from wheels and tires. So saving potential is huge.



It is not wise to put 255/45R19 tires to your family car if your goal is to maximize the range. I have already proven that there is easily 10% savings potential in Model Y, but more accurate estimation suggest 12-15% savings when everything is done rigth.


Some manufacturers are running wiser tire sizes than others. but there is more to this than just tire size as aerodynamics are so important. I have seen good trends like in BMW IX1 205/65R17 size when taking measurements, also 205/55R19 from goodyear used in Renault looked very aerodynamic, but those I havent yet measured.

My plan is to prove you can have good driving characteristics even with tall and narrow tires.

[CapriRacer]

Vekke,

I think that is wrong. I've seen values of 17% total for tires, but that seems to be for the US EPA fuel economy test. Personally, I think 17% is too low.

But I don't think 50% is right either. If 50% were true, then changing tires should have drastic differences, and while they have differences, but it's more of the order of 10% change for fossil fueled cars. EV's would be better, but 50% sounds too high!

Plus there's the issue of not being able to eliminate a lot of the energy consumption tires contribute.

But if you're saying that tires contribute 50% of the energy consumption for a vehicle while it is traveling at a moderate speed, that might be true. But getting all that weight moving, then using regeneration braking as the only means for stopping the EV, there's losses in the braking that still makes that whole thing worse.

[Vekke]

It's not a easy puzzle. Some say 15% for wheel drag. That seems way too low.

Modern evs drag coefficient is under 0.25 so wheels impact is bigger than some time ago with fossil cars.

Weigth of them are generally also high so rolling plays bigger impact.

Then you add the fact most evs have very wide tires.

That 40% aero drag from wheels and tires I got by using 0.09 Cd increase to model y which is 0.23 car.

10% savings were reached easily without optimizing the tire deflectors, just with 195/60r18 tires, and the offset was also not optimal in first tests.

I have calculated 20% savings when optimizing deflectors for narrower tires.

[oil pan 4]

My leaf uses most of it's power to beat its way through the air.

[freebeard]

Why not not just have just three wheels?

[Vekke]

Weigth loss potential is so much that its actually running on 3 (weigth wise) compared to the stock 255/45R19 at least in the Tesla Model Y which one tire weigths 25kg with wheelcovers on.

Ofcourse that is not true if you have smaller wheels and tires from start.

[rmay635703]

It was always my assumption that

Tire+Rim/Wheel drag was RR + Aero drag

Tires have a compound effect where going from a small tire to larger tires may have lower RR but the dynamic drag and suspended weight might exceed RR gains.

If the article is saying RR + Aero resistance is 50% on 4 tires that may be accurate at higher speeds depending on the body design

[freebeard]

This is why both Buckminster Fuller (Dymaxion) and Jocko Johnson (Triple Nickel) proposed three-wheel vehicles that fly the rear wheel at high speeds.

Tail-draggers, if you will.

[j-c-c]

I put 295x35/18 on my 2nd gen rear wheel drive Tacoma PU, lost a bit under 2 mpg, but it cornered great, handled great, stopped great, and tolerated soft ground/grass rather well. I felt that was worthy bang for buck. The extra rolling resistance in rain/standing water seemed rather high and mpg plummeted.

[Phase]

the tire size on the new 2023 prius LE is P195/60R17

what are your estimates in fuel economy improvement if dropping those down to 15 inch wheels?