Hey yall. Im driving a 06FX4 extended cab.......Has anyone gone from the stock to a 255/70/18 tire size? Im running E-rated 275/70/18 Duratracks right now and getting 12ish mpg. Wondering if the skinner smaller lighter tires will look terrible or if it will help alot. I know most guys are looking to upsize but the current economy is eating us alive and Im looking for ways to hang onto my truck through this. Any pics with that size would be amazing. Than ks for any help!

 

Best deal in wheels/tires IMO is buying a nice set of factory “takeoffs”, I can usually find complete set (wheels and tires) for less than what a full set of new tires (mounted balanced out door) would have cost.

just go back to factory sizing and factory rating (ie not load E) and make sure computer/pcm is set for sizing you are running. You should see ~ 25ish-% improvement (12ish to 15ish) if rest of truck setup is stock and running properly.

 

Going to a smaller diameter tire will decrease your mileage as your engine will be turning
more RPM's. It has the same effect as installing a lower gear ratio.

 

there are more factors than just diameter. If there weren’t, installing huge tires would be more efficient.

in general, the oem spec’d tires will run most efficiently.

 

The smaller tire is only 1" shorter. It won't look much different. The percent difference is only 3.5%. Not going to make the 12mpg become much better, maybe 14 if you are lucky, if you also get away from the heavy E-rated tire. A few pounds per tire and slightly smaller tire will show results, but not make it a remarkable change.

Are you basing your 12 mpg off of an incorrect speedometer. Again, only 3.5% off but enough to factor the MPG calculations by a little. You might be getting close to 14 now if you haven't calibrated the odometer. With that, if you are driving that truck around town getting 14mpg, you are doing as good as it gets.

In short, no it won't look terrible and no it will not help alot.

Next thought is you want to increase your mpg to reduce the price at the pump? Are you going to the tire store to spend $900+ on tires. You should do a years worth of calculation of how much you will spend in gas at today's mpg and if you add 2 mpg, say 14 mpg on your annual mileage vs 12 mpg at your annual mileage. Is the difference going to make $900 worth of tires an effective change? Are you going to replace with use tires -you need to be selective to find tires that are evenly worn and about 1/2 tread life or more. Less than half the tread life then you're compromising tire quality.

If you can get 300 miles out of a 24 gallon tank, that will increase to 350 miles per tank with a 2mpg increase. That is about 3 gallons worth of free fuel per tank, or 13-bucks at $4.50/gallon. You need about 70 tanks with a $13 savings per tank to equal $900. My math may be a bit wonky but I think I got it close (not considering rounding errors)

Do you have 2 vehicles? If so, I'm sure you are already parking the truck as much as possible. If it is a 1-vehicle family, yeah that eats up gas a lot more quickly. I have a 1-vehicle neighbor and that truck is always leaving the house. He's taking kids to/from school and who knows what else during the day when he leaves at odd times. It's the 5.4 model (I'm pretty sure).

 

Your stock size looks to be 275/65r18. I’d go with that size with some P Metric Michelin all seasons (or something similar) if you want good fuel economy. You’ll probably shed 15 lbs per tire dropping the LT load E.

 

Get a decent set of HT oem size tires, get the right foot a Pb removal kit and put an egg under the foot pedal.

stop driving like the road begins at the end of the hood and anticipate lights and other traffic issues.

 

275/65/18 is factory size. I had 275/70/18's for a few years, but went to 265/70/18's as a happy compromise. No real difference in fuel mileage with either of the 3 sizes, but the 275/70/18's are only available in a much more expensive LT tire. 265/70/18 was the largest non-LT tire I could find. Saved some money when buying them, none at the pump.

IME it isn't tire size or weight so much as tread pattern. The Duratracs are a pretty aggressive tire. Something with a milder tread may help a little. Around 14 mpg is about as much as you can expect with that truck with any tire. If you NEED new tires right now then choosing something a LITTLE smaller MIGHT help some. But don't go out and buy new tires when you don't need them expecting to save money. You'll spend way more on the tires than you'll save in gas.

Factoring for the odometer being off by such a tiny amount will only change fuel mileage by no more than 1/2 mpg. Probably only .1 or .2 mpg.

 

Thanks for the replies everyone. I guess I should have mentioned that the 275/70's will need replacing this year anyway. I wouldn't just switch out for MPG only that wouldn't make too much sense budget wise, like someone mentioned. Since I don't work on muddy mountainous jobsites anymore I figured Id go with a straight up street tire hoping to lighten the weight lessen the rolling resistance, and get some MPG back. Im not expecting anything miraculous but if I could get it to run 15-16MPG with a light foot it would be a big help.

Does anyone have a pic of a similar truck running 255/70/18's? Recommendations on a budget, good performing street tire or all season/HT? Also my brother in law was telling me some things to do mechanically to raise the MPG, like running seafoam in the intake and about 3 other things. Im not super mechanical at all so Im making a list of things to do to research heavily. Good luck out there to all of you struggling right now. Thanks everyone.

 

It will look stock with stock size tirtes. The shorter stock tires will enhance braking though you may very well NOT notice it. Stock size will also enhance acceleration, but again you may not notice it. Stock tires will be lighter than the over size tires with most weight out near the tread surface that is likely wider, longer around tire circumfrence, and depending on the tire, maybe just a heavier tread. Tires act like flywheels, they devour energy in the spin up from stop, they store energy thus take more effort to come back to rest. Being taller, they act like a longer wrench too. The weight of the tires is unsprung weight so that works on suspension more, wearing parts faster.