MB4runner

Hi, I have a 3.0 v6 auto, 4.88s, I want to maximize city driving fuel mileage. Currently I have 31 x 10.5 tires. Should I go to 235/75/15
or what do you suggest?

charliestoytruck

im not an expert at all but the bigger tires would do the same speed at a lower rpm, just works harder to get there, if all your driving is in city then small tires are better, if you run open roads then im not sure. . .

Swimmerboy2112

iTrader: (2)

For what it's worth,

with my 4.10 gears and 2" lift, running 30's got me 20-22mpg and when i went back to 28's i get 19-20mpgs granted this is about a 50/50 mix of city and highway but something to think about.

MB4runner

Thanks guys thats what i think too, if taller is better for highway, so im assuming shorter is better for stop and go city driving.

And I do 100% city driving

pinoaktwh

Are you guys compensating your calculations for the tire size difference. Meaning your miles driven will be different on your odometer with smaller to bigger tires.

When you put bigger tires on your truck your odometer will show less miles driven(worse mileage), smaller tires will show more miles driven(better mileage).

Now granted bigger tires Will get you less miles per gallon because you have to get them going.

Just asking, most people I have found never adjusted for that change, making thier mileage math "off".

charliestoytruck

good point i didnt do any ,math just thought of principle's at play. my mud truck is off road only so i measure the gallons to the mile lol

JJ'89

lightest, skinniest, highest pressure; wider means more aero drag, and more rubber scrubbing in anything but straight-ahead...heavier means more rotational inertia...

T_F_E

definetly go back to stock if you want mpg.

MB4runner

Thanks guys. This truck is new to me, I'm going to finish this tank on the 31s and then switch to smaller tires and compare the mileage. Then I'm going to due a tuneup and compare again. Ill post the results in a week or so!

Swimmerboy2112

iTrader: (2)

Yes i compensated for the speedo being off.

peow130

Skinny, light tires.
30x9.5 is a good size, and better in the snow than a 31x10.5.

4Crawler

iTrader: (3)

With that engine/trans/gear combo, 31x10.50 was the stock tire size.

InvaderTrax

Yeah I wouldn't go with a smaller tire for those gears. If you don't care about having big tires, you could always find someone to swap their 4.10's and small tires for your stuff plus a decent amount of cash

MB4runner

Yeah I figured the 31's were stock, I guess my main question is: If I do 100% city driving, and I go down to 29" tires with the 4.88s will I get better MPG? Yes or no?

I think I will because it will use way less throttle and gas to stop and go all day long.

If I ever plan a long trip, I will put the old 31's back on for better highway mileage.

coops2k

since you are talking about using this tire for just street, guessing that you will have a 2nd set for fun, I would go with a good passenger car or light truck tire in a 225/75/15 that is designed for improved MPG.

here is a good read on how tire sizes can affect a car
http://www.caranddriver.com/features...sted-tech_dept