Yaris Tire size and Fuel Economy

[77W]

Hi

I am wondering as if using P175/65/R14 would result in better fuel economy that P185/60/R15 tires on Yaris Sedans ? 10mm of lesser tire width should result in lesser friction between tires and road thus lesser (better) fuel burn.

Any experiences ?

Regards

77W

[Loren]

Makes a difference, but I'm presently running 215's and still easily getting 38-40 mpg average around town. More important is that they are properly inflated.

If you do a lot of highway driving, running a slightly larger diameter tire (like a 175/70-14) will effectively raise the final drive ratio, reduce engine rpm and save some fuel.

[Cosworth]

Punch in the tire sizes at: http://www.miata.net/garage/tirecalc.html

You'll notice the 14" tire spinning faster than the 15" tire at the same speed. This will result in the rpm being slightly higher at highway speed. So, any gain you might have in 10mm narrower tire will be wiped off.

[talnlnky]

they are right... for city 14 would be best... for hwy driving 15" would probably be best. I've often thought about upgrading from 15 to 16" since I do about 70% hwy.

[Yaryaryaris]

That tire size calculator just went to my favorites. Very helpfull.

So what is the stock tire size on Yaris HB's? I currently have 195/60/15's but believe they are larger than stock.

Brenton

[Loren]

Don't get too wrapped up in wheel size, guys. It's the diameter of the TIRE that is important here.

[YarisSedan]

I do know when i jumped to 205s my milage went down 1-2mpg so going down a size i would suspect you may gain 1mpg

[why?]

Also weight. Weight can vary quite a bit even in tires that are the same size. Unsprung weight effects everything more, and supposedly rotational mass of the tires effects it even more. I read somewhere that 1 lb on the tire is like 4 lbs above the suspension. Not sure if it is true or not.

[jonismyname]

Originally Posted by Loren

Don't get too wrapped up in wheel size, guys. It's the diameter of the TIRE that is important here.

my 14" wheels wear winter tires the same diameter (circumference) as my 15" summer wheels. circumference counts, not rim size.

larger tires will also display less fuel economy than is being achieved as the vehicle will travel further than will be displayed (unless using scangauge type tool to compensate).