Tire width impact on fuel economy / MPG

[ksa8907]

What about commercial truck tires, duals vs single? Don't they claim rolling resistance reduction?

[aerohead]

Originally Posted by ksa8907

What about commercial truck tires, duals vs single? Don't they claim rolling resistance reduction?

Originally,in the 1980s,the super-single,'floatation' tires were credited with a 20% reduction in rolling resistance.

[freebeard]

Given the depth being brought out in this discussion, perhaps I should pose this question:



OEM on the Dasher was 13", there is a rusty dry-rotted example in the spare tire well. Current fitment is 14x~6.5" Ronal R-8s with 195-60/14s. What I choose as a goal is to have a summer and winter set of wheels, to spread out wear and replacement (yeah, right). The summer wheels at 14" locks in the 195/60 size circumference. I can't afford to lose the current overall ratio.

For winter what I would like is 15" steelies. What I understand is that mud, snow and ice all require difference treads and compounds. Sidewalls that virtue signal battlecar status is probably more important than actual off-road performance.

Hydroplaning resistance is right up there.

[aerohead]

Living in basically a 3-season clime,I've never had to face a 'real' winter at home.Snow is pretty rare.
I have driven in the snows of Texas,New Mexico,Colorado,Utah,Wyoming,........... up into southern Canada.All on all-season radials.
They weren't perfect but they did get me there and home okay.
I suspect that there are some really killer ice and snow tires out there.
Subaru's appear to be undaunted in ice driving.

[westygo]

Well I just found 4 brand new Civic SI rims at a dealership, removed from a '18 civic at a good price. Dealership offers Michelin defender t & h tires and BF Goodrich Advantage TA's in the size I need.
Going to look up RR on those and investigate a couple others too. The rims are pretty flat with moderate size holes, but overall pretty aero.

[westygo]

[westygo]

They are going to look pretty swank on my 20 year old beige dad van...

[California98Civic]

Originally Posted by aerohead

Some other reports which confirmed a direct correlation between tire width and aero drag were found with the:
*Pontiac Trans Am
*Subaru XT
Also,many of the lowest drag concept cars ran narrow tires as a low-drag strategy,including:
*GM Aero 2000
*GM Aero 2002
*GM Aero 2003
*Renault Vesta-II
*Ford Probe-IV
*LOREMO
*Daihatsu UFE I,II,III
*VW 1-Liter 2002
*VW 1L c 2009
*VW XL1 2016

Thx aeohead. If it was part of the plan for the XL1, then that settles it for me. But Capriracer's point above that tires have less air flow exposure than we might assume because they are mostly in the wheel well... How significant, do you think that is?

[freebeard]

...because they are mostly in the wheel well... How significant, do you think that is?

Wheels are actually pretty generic, wheel wells vary as much as people's belly buttons.

[Vman455]

Originally Posted by California98Civic

Thx aeohead. If it was part of the plan for the XL1, then that settles it for me. But Capriracer's point above that tires have less air flow exposure than we might assume because they are mostly in the wheel well... How significant, do you think that is?

Well (ha ha!), Hucho cites two researchers who found that "the flow around the lower part of a wheel remains very much the same as for a free wheel, and according to A. Morelli a wheel's drag coefficient (referenced to its own exposed frontal area) remains almost constant." The effect here seems clear: smaller tire=less drag. And in yaw, which front tires typically experience ~15 degrees, the drag increases 3x, so any reduction in area would have more effect as well.

However, since we're working with production cars, there is another consideration, wheel housing volume to wheel volume ratio. As that ratio increases (as you would get fitting a narrower, lower volume tire in an existing wheel housing), drag goes up too, about ten counts for every doubling of the ratio. And lift coefficient increases 5x as fast, 50 counts for every doubling. But, it's unclear what effect a smaller volume, narrow tire that still fills the area of the wheel opening would have; Hucho doesn't cite any data on that, and while I think I have a PDF or two on that, they're on my other computer. I'll see if I can find them tomorrow.