Wider Tires = Lower MPG?

[X~FACTOR]

After upgrading my wife's Rav4 wheel/Tire combo from 215/75-16 to 255/55-17, the MPG went from steady 26-27 mpg to 21-22 after 5 full tank. Will I experience the same result if I did this to my X, going from stock 235 to 255, or worse, 275?

 

[Doug]

I would imagine a wider tire could cause lower gas mileage. Mostly due to the fact the tire is heavier and needs more power to get it moving. And you'll most likely experience the same thing with your explorer though it may not be as drastic.

 

[Hokie]

F = ma

The friction force of the tires is based on the coefficient of friction of the tire times the weight of the vehicle

What does this mean?

You increase the tire width, you increase rolling resistance, and no doubt you went to a sticker, better handling tire.

This is why you see economy tires on these skinny little donuts inflated to 50 psi.

Yeup, you just caused yourself to use more gas by making it handle better

Ain't this game fun?

 

[Hokie]

Yes, your Explorer's mileage will drop. Its an omen.

If its gonna drop regardless, that is your Explorers way of saying "I'm a 4x4 dumba$$, lift me and get me dirty!" The crystal ball says you will have bad kharma until you do so.

 

[Alec]

That's still a huge drop on the other truck. Hmm....

EDIT: Oh, sorry: car

 

[aldive]

Wider tires will definately cause a drop in mileage.

 

[X~FACTOR]

Yea, Alec, 5 mpg drop is too much. Some Rav4 cars come with 235 tires standard so, basically, I just went 2 plus sizes ONLY.

Hokie- guess what? I'm thinking of lowering that Rav4. Eibach Springs are only $198 per set.

 

[zensius]

I can't do the math...but are those two tires the same diameter? If not. A larger tire has to turn fewer times to go the same distance. So you speedo is reading less for the same distance. Thus your computations would show lower mpg.

 

[X~FACTOR]

Good question- I THINK the tires were 215/75 or it could've been 215/70. But either way I remember doing the math at the time when I bought them and they came in within 0.1 of each other. So that part is fine.

 

[Alec]

Actually, you went from 28.7 x 8.5 to
28 x 10

My brain isn't working right, so let me type this through: your tires will spin faster, your speedo and odo will go faster....Thus it should appear that you're going more miles per gas used.

Something's fishy. Either my brain is totally fubared (I'm sick), or your Rav4 is screwy

 

[bipolarbob]

Originally posted by Hokie



Yeup, you just caused yourself to use more gas by making it handle better

Ain't this game fun?

Ha Ha ! That is funny! Sad but true.

 

[X~FACTOR]

Originally posted by Alec
Actually, you went from 28.7 x 8.5 to
28 x 10

I got it. The tires before were 215/70-16 (not 75 series) and that equaled 27.9" tall. Now I am running 28.0". So 0.1" is all the difference. So I figured its all about the width and not the height that is the problem.

 

[410Fortune]

also the correct tire pressure has ALOT to do with mileage...

PLus new tires need to be broken in a little, mileage will improve.

You can also test the tire pressure and make sure they are filled to a point where you will still get even wear and have as much pressure as possible.......

 

[X~FACTOR]

You are right. I haven't checked that at all since they were delivered a month or so ago.

 

[james t]

your new tire/wheel package is alot heavier than the old. a may-pop 215 weighs nothing compared to a sport truck 255/17.

 

[Hokie]

did you get new wheels too? tire size is not the verdict here. rolling resistance by both friction and the increased polar moment of inertia (resistance to rolling) are.

My mileage on my truck 'appears' 1 mpg lower b/c on a 300 mile trip, my odo reads 19 miles low ~ due to 32" tires. My actual mileage dropped b/c of what I just stated.

 

[410Fortune]

okay well anytime you cahnge tire rolling diameter the speedometer/odometer must be corrected, otherwise the computer will be FUbared on these newer cars.

Since you changed rolling diameter dont use the cars computer to calculate your mileage, and you cant rely on the odometer until it is calibrated.

 

[Alec]

.1" won't make a **** a difference in the speedo or odo.

I guess it's the mass and friction. Welcome to car modding!

 

[james t]

really, it is just the added weight. if you've ever picked up a little cheapo 215/70/16 or a rigid/thick sport truck type 255/55/17 you would realize the 17" sport truck tire weighs considerably more. add that to the fact that a wider 17" wheel weighs more than a stock 16x7, and there is your issue.

nothing new Xfactor, we all go through it to varying degrees.

 

[jjue]

Although 5 mpg is on the extreme side of milage drop, I believe it since the tires weigh more, and the Rav4 doesn't have the umph to turn those tires without working a whole lot harder, using more gas. On our explorers, especially the V8, adding accessories and larger tires don't affect us since we have the low end torque to begin with.