Tire size effect on mileage...

[scott42]

does it have any? I know that a change in overall tire size/diameter/circum throws off the speedometer, but does it affect mileage?
How are the odometers set to read I guess would be the key?
Any Ideas?
This calculator shows speed changes...
but no reference to mileage
http://www.miata.net/garage/tirecalc.html

 

[SomaMP3]

Not sure about that....i have 15" winter tires on now but i can't notice a enormous change in speedometer readings...i did notice though that my odometer was kinda off while doing one of those odometer checks on the highway....it was off buy about.4 kms?

 

[andr3w]

I run 195/55/15's as snow tires which makes it look like I am going 4% faster than I really am, and I my odometer is reporting 4% more miles. Should have tried to get the aspect ratio closer but took a cheap package with decent looking alloys.

 

[Rogue]

A smaller tire will give you less gas mileage because it spins faster, but travels less distance:

Stock tire (195/50/16) = 74.35 in. Circumference [188.8 cm]
Winter tire (195/55/15) = 73.62 in. Circum. [187 cm]

Mileage = 350 mi/14.1 gal = @25 mpg [563.3 km/53.37 L = @10.55kmL]

1 Mile = 63,360 in
1 Mile = 1.609 km
1 km = 100,000 cm

Now in 350 miles your stock tire will have turned 298,264.96 times. Let's say winter tire turned that many times, you'd only have travelled 21,958,266.36 in. (346.56 mi) which is a 1% loss in mileage.

For the Canadians:
Now in 563.3 km your stock tire will have turned 298,358.05 times. Let's say winter tire turned that many times, you'd only have travelled 55,792,955.35 cm (557.92 km) which is a 1% loss in mileage.

**Note: I did these calculations at 1:30 AM. I'm also assumming that driving conditions were exact for both tires (including shift points, turns, etc.) PLEASE FEEL FREE TO CORRECT ME

(2thumbs)

 

[ACruzR]

Don't forget to factor in the power needed to turn the larger wheel. I owned a 4x4 for 15 years and switching back and forth from larger to smaller tires (225 to 31") definitely affected the gas mileage - (reduced). But that was a much larger increase than say going from a 205 to 215 or to 195. Pretty much you can look at it this way: larger tires=larger diameter to turn, less HP to the wheel, more HP needed to drive the vehicle, higher gas milage.
But who knows I typed this up at 12:30 am and very drunk. I don't even know why I'm here.

 

[cjstringer]

It also depends on if you drive highway or city most of the time. If you have a little larger diameter and drive on the highway all the time, you may improve your gas mileage if you are a cruis-control type driver.
Just a thought.