I have an ’08 F450 with the 6.4L with a 4.30 rear end. I am going to need tires soon and the 225/70R19.5 is not the most common size out there. If I go up to a 20” or 22” wheel, I will have a larger selection of tires. I do want to keep the G rating, so I cannot go to a smaller wheel. I know the larger wheel will in effect change my gear ratio, but the question is- will the larger wheel help or hurt my mileage? The 450 has more horsepower and torque than I need, I just want to make sure that I don’t hurt the little mileage I have. I get around 12 – 13 mpg on the highway (empty) and 9 – 10 mpg with my camper loaded (see photo). I am still under warranty and therefore won’t add a programmer yet. I am aware that the wheel change may also raise red flags at Ford, and yes, I know all about the Magnuson-Moss Act, but I don’t want to take on FOMOCO in my spare time.

Sorry- I rambled here. Thanks for any input.

 

It might not be that easy. You can buy light wheels in 20 or bigger size and match the tire to have the same rolling circumference than the original one.
The manufacturers use rpm, what means rounds per mile to determinate rolling size of the tires, so get familiar with that term.
But those fancy oversized rims are not design for superduty pickups. Do you have an idea about the prices.
I do have 19.5 wheels on my Ford and I do have 22.5 commercial wheels on my motorhome.
Trust me -there is no way you can fit 190 lb wheel on the Ford.
Go to local tire shop for better advise. I am using a shop that was recommended to me by a friend 12 years ago and the same owner runs it for like 40 years.
They offered me the best prices and services -not something what Less Swab, or American Tire with HS dropouts working there can match.
BTW the 22.5 Michelin cost me $550 few years ago. A piece.

 

Gearing is a funny thing with these trucks. In the old days, you used to be able to swap a 3.42 gear set for something like a 2.87 set and get better mileage. Today, it just isn't that easy.

You already know that a larger circumference tire will raise the effective gear ratio of your vehicle. But you want to know what that will do to fuel consumption.

There is no easy answer.

First, if you do a lot of city driving (especially while towing or hauling heavy loads) you might see a decrease in mileage. These trucks are not lightweights, it takes some torque to get them moving. if you lower the torque multiplication of the effective ratio, you have to make up for that by leaning on the throttle a little more to get your rig moving.

Second, an increase in ride height from the larger tires usually means more wind resistance. This will be noticeable if you do a lot of highway miles.

Third, lowering your cruising RPM on the highway should be a good thing, and should decrease fuel consumption.

Fourth, will the new wheel/tire combination be lighter or heavier. More weight = less mileage.

Lastly, will the new tires have more or less rolling resistance? Any gains in highways miles due to lower cruising RPMs may be negated by a higher rolling resistance.

There are companies that make custom wheels for DRW trucks that will be built specifically for your vehicle, so fitting should not be an issue. Off the top of my head I can name Dima Custom Wheels (you see them on a lot of DRW show trucks) but can't recommend them over any other shop.

Custom Wheels by Dima

 

You'll want to make sure that the wheels are actually rated for the load you're carrying.

 

Thanks Kajtek1, redford, and smlford, I appreciate all your input.