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37's to stock tires, mpg gains?

11K views 39 replies 16 participants last post by  Über Drunk 
#1 ·
Hey everyone, quick question I'm trying to estimate.
I currently have 37" mud grapplers in a 6" lift and get horrible mpg, to be expected haha.

How much mpg would I get back if I put stock size tires back on?

I'm moving from AK to OR and driving down and am putting some stock tires back on for the trip haha, it will look ugly but only for a week and it'll save my nice tires and I'll get way better mpg.
 
#3 ·
That's what I was thinking too but don't you lose some mpg from lifting your truck too?
 
#4 ·
Of course, the aero is not quite as good. And maybe the drivetrain angles add a bit. I would think it might lower it 10%. But by far, the 37"s (both the weight and the drive ratio change they represent) would be the biggest factor.
 
#5 ·
Awesome! Yeah I just bought some used "summer" tires for $200 for the set. Great condition so then I'll just sell them again when I get to Oregon. Totally worth the savings in gas for a 2500 mile trip
 
#7 ·
Haha definitely will! Just picked the tires up, I'll get them mounted tomorrow
 
#11 ·
I'll quote myself from another post I made on here after I put 37s on.


Running huge tires will destroy gas mileage

Meh, not really

Not to burst everyone’s bubble, but the actual number of miles your truck travels per every gallon of fuel burned is probably not significantly worse with larger tires. The reason your miles per gallon looks terrible is because the number of rotations per mile hasn’t been corrected. If you’ve corrected your speedometer, your mpg computer MAY be reading about right (depends on your solution to fixing the speedo), but here is the typical reaction:

“I put a lift and bigger tires on my truck and now I get terrible gas mileage! Eff you Toyota! Wah wah wah!”

When we replaced our 33s with 37s, our mileage did indeed drop to about 12 mpg from about 15mpg. “Oh my God, the sky is falling!!! How will we ever afford steak again?!?!” To see if we could still eat like royalty (or at least not have to survive on cat food) I did the maths…



Let’s look closer at those last three columns – they’re the important ones…



Basically, the truck thinks it has driven a mile for every 628.3 rotations of the tires (this is based on the stock tire size of 275/65-18 for a 2014 DC 4x4 SR5). 628.3 rotations of a 37” tire takes you farther than 628.3 rotations of a 32.1” tire. 1.15265 miles to be almost exact.

So, if I take the 12 mpg my truck says I’m getting, and multiply that by the 1.1526 miles we actually travel for every mile the truck ‘thinks’ we drove, I’m actually getting 13.8 miles per gallon – that is only 1.2 mpg worse than stock tires – on 37s (13.5 inches wide too, not 12.5). If I believed my trip computer I would think I lost 3 mpg, but really only lost 1.2.

Math is fun kids.

Here’s a cheat sheet for anyone interested but lazy. To find your actual mpg, take what the computer says (or you calculate by hand) and multiply it according to this list:

For 33” tires, multiply by 1.03
For 35” tires, multiply by 1.09
For 37” tires, multiply by 1.15

______________________________________________

I should note here that I'm not implying that you are whining about mpg as I implied above - I just quoted myself about general reactions to bad mpg due to bigger tires
 
#14 ·
@KevinK thanks for forwarding that info. Interesting points, I do realize my mpg is slightly skewed with the speedo not being corrected, but it sure does feel worse too. I watch my gas needle go down as I'm driving around haha
 
#19 ·
Yeah gas is about 2.50 here right now. Double that for while I'm driving through Canada haha.
@dudleyh transferring for work. I'll be back to Alaska someday, I love it here!
 
#21 ·
Some of us plan to drive from Arizona and Southern California up to Denali sometime next year. I assume our path will take us through Oregon - you could be our Alaskan tour guide!


Tapatalk - because smoke signals would be too easy.
 
#22 ·
I actually lived in Portland for 14 years before AK. Been in AK just over 4 years now heading back to OR. Bittersweet, I'll miss it here for sure but I love Portland too. So it's all good, I'm choosing to transfer =)
 
#23 ·
Alright, you guys ready for this!? Haha here ya go
 
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#25 ·
Make sure you flatten the bill on your hat while you're driving it like that.

I miss Alaska everyday, chilcoot Charlie's, Darwin's theory and humpys, oh and the last (fat) frontier were our spots.

Good luck in Oregon dude. Oh and watch out for the old man with the cane on the Alaskan highway.
 
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#28 ·
Hey! I just got to Oregon yesterday! And YES! I was quite surprised, with the smaller summer tires (275/55R20) AND pulling a 6x12 uhaul trailer, I averaged about 11.5 mpg. Which I'm super excited about. I get like 9-10 mpg with the 37's without pulling a trailer haha.

So it was definitely worth it
 
#30 ·
Did you run into the old man with the cane on the alcan anytime?
 
#32 ·
Haha nope didn't see him

Glad you made it!

If you multiply the 9-10 mpg you were seeing on the 37s by the corrected number of miles actually travelled, you were actually getting 10.35-11.5 mpg on the 37s.

Not great by any means, but better than 9-10.


Tapatalk - because smoke signals would be too easy.
Right, thanks for the clarification. Still totally worth it




Sent from my iPad using Tapatalk
 
#34 ·
*goes out and buys plywood*
 
#36 ·
Haha I'll probably get some hate on this one but not a big football fan. However, my older bro was a Beaver so I'd have to pick them
 
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