Fuel savings 165/80/r14 175/70/r14

[Somerandombeing]

Good morning,

I would like to know roughly how much fuel would i save from going from a 175/70/r14 tire champiro vp1 to a 165/80/r14 highfly hf201 tire. Both tires have same rolling resistance / fuel efficiency level "E" according to eu tire rating scale from "a" most efficient to "g" less efficient? Both tires have same rolling resistance the highflys have a 10mm thinner width so that is a smaller contact patch and the highflys have a larger circunference so at highwat speeds the tire rotates less to cover same distance which means less rpms equals less fuel, correct me please if i am wrong.

thanks

[Draigflag]

I'm no expert, but seeing as the tyres have identical fuel economy ratings, I doubt you'll notice any significant difference. You'd be looking at fractions of fractions.

[Somerandombeing]

Why do vehicles in fuel economy competitions have skinny narrow tires though?

[Draigflag]

Yea they are super narrow, but you're talking about a 1cm difference between tyres, and that's the width, the comparable contact patch is even smaller than that.

[JockoT]

Even identical to the tyres replaced, new tyres return poorer mpg for about 3 - 4,000 miles. The best economy comes from worn-out tyres, just before you replace them.

[trollbait]

The skinny narrow tires in competitions are for reduced aero drag. They are also likely at pressures you don't want for every day driving. There is too slight of a difference here between the tires to really change this.

Contact patch size depends on the tire pressure, load weight, and tire design, in addition to tire size. Narrower tires do have a thinner contact patch, but the patch size also gets longer. There may not be much change in the area between them.

The change in revolutions per mile changes the effect final gear ratio, so the engine can work less per mile. Be sure to factor in the speedometer adjustment to the odometer reading to get the correct fuel economy results.

Some tire size calculators.
https://tiresize.com/comparison/
This one goes in depth.
BND TechSource - Tire Data Calculator

[accelrok]

Thanks for the information regarding the fuel economy of tires. I think choosing a lighter wheel can help with the fuel mileage as well. I got a set of HD wheels at the start of the year which is significantly lighter than my previous wheels. There's an improvement with the mileage compared to running with steel wheels.