New Prius

[aerohead]

Originally Posted by Phase

Smaller wheels usually give better mpg. Even Toyotas website and teslas websites show range and mpg being improved with smaller tires.

1) You, Wayne, and the Prius forum are not identifying any mechanisms which can be attributed to the alleged improvement in mpg. 'Smaller' wheels is meaningless unless you provide conditional specifics.
2) EPA HWY ratings are meaningless within the context of the 'real world.' This value is 'fudged' from data obtained in a way which is impossible for us, unless it's done in a test cell, on a dyno, exactly like EPA Mobile Sources does.
3) At 70-mph, I can get anywhere from 43-mpg, to 99-mpg in a Gen-2 Prius, 'depending' on 'conditions.' My neighbor, with the 2022 Prius saw up to 80-mpg between Denton, TX and Oshkosh, Wisconsin. These kinds of data have value 'ONLY' if all the accompanying conditions are captured for the event.
4) For your 'small wheel' argument you've introduced:
A) a frontal area unknown
B) a rolling force coefficient unknown
C) a polar moment of inertia unknown
D) a wheel offset unknown
E) a wheel-arch gap unknown
F) a wheel porosity ventilation drag unknown
That's six unknowns that aren't accounted for, and until they are, your just 'throwing ---- at the wall, and looking to see if anything sticks'.
You guys need to put your heads together, and get into the 'weeds'.

[Phase]

Originally Posted by aerohead

1) You, Wayne, and the Prius forum are not identifying any mechanisms which can be attributed to the alleged improvement in mpg. 'Smaller' wheels is meaningless unless you provide conditional specifics.
2) EPA HWY ratings are meaningless within the context of the 'real world.' This value is 'fudged' from data obtained in a way which is impossible for us, unless it's done in a test cell, on a dyno, exactly like EPA Mobile Sources does.
3) At 70-mph, I can get anywhere from 43-mpg, to 99-mpg in a Gen-2 Prius, 'depending' on 'conditions.' My neighbor, with the 2022 Prius saw up to 80-mpg between Denton, TX and Oshkosh, Wisconsin. These kinds of data have value 'ONLY' if all the accompanying conditions are captured for the event.
4) For your 'small wheel' argument you've introduced:
A) a frontal area unknown
B) a rolling force coefficient unknown
C) a polar moment of inertia unknown
D) a wheel offset unknown
E) a wheel-arch gap unknown
F) a wheel porosity ventilation drag unknown
That's six unknowns that aren't accounted for, and until they are, your just 'throwing ---- at the wall, and looking to see if anything sticks'.
You guys need to put your heads together, and get into the 'weeds'.

Idk why you’re putting me in the same category as Wayne. He’s the one claiming big wheels rob fuel. I’m
The one who’s been asking why. I even made a dedicated thread asking why.

He did two identical steady state tests with the new Prius. No wind. Flat roads. Almost same temps outside. The smaller wheels gave better mpg. This isn’t the only time it’s happened. He’s compared countless cars with the same tests. From the Ioniq hybrid with 17 versus 15 inch wheels. Electric car range tester in Kia and Audi EVs. Also niro hybrid. The list goes on of him testing the same car models with different wheel sizes. You can’t deny the evidence. There hasn’t been a single case tested with bigger tires giving better gas mileage.

[Piotrsko]

How about we define tire size by the outside diameter and possibly installed weight of the assembly? Stops most arguments about effects of RIM size.

[aerohead]

Originally Posted by Phase

Idk why you’re putting me in the same category as Wayne. He’s the one claiming big wheels rob fuel. I’m
The one who’s been asking why. I even made a dedicated thread asking why.

He did two identical steady state tests with the new Prius. No wind. Flat roads. Almost same temps outside. The smaller wheels gave better mpg. This isn’t the only time it’s happened. He’s compared countless cars with the same tests. From the Ioniq hybrid with 17 versus 15 inch wheels. Electric car range tester in Kia and Audi EVs. Also niro hybrid. The list goes on of him testing the same car models with different wheel sizes. You can’t deny the evidence. There hasn’t been a single case tested with bigger tires giving better gas mileage.

You still don't understand that, when you refer to 'smaller' wheels being the only criteria for the observed improvement in fuel economy that, you're tasked with answering the 'six' questions related to the 'smaller' wheels which would be necessary to 'explain' the observed phenomena.
You could not be over-simplifying the comparison any more than if it had been your intention to do so.

[cRiPpLe_rOoStEr]

A bigger-diameter tire may improve fuel economy under certain circumstances, yet the weight might become an issue. But usually, a narrower tread may sort of compensate that. And the weight of the vehicle increasing the pressure between the tire tread and the pavement may not be so bad when it comes to grip. Just look at how some snow tires are noticeably narrower than all-weather tires. I remember seeing charts mentioning snow tires with a 135 tread being suitable to cars which often resort to 185 or 205 treads on all-season tires.