I have a 2005 6.0 F350 club cab, long bed not a dually, 4wd.  It came with 18 inch wheels.

I am considering putting smaller wheels on it.  I am interested in opinions about this.  Will it increase the mileage?  Will it be a better tow vehicle for my 3 horse steel gn (I think about 5600 pounds)?  Will it be more stable on snow? Can the related computer things - mileage calculators, speedometer, odometer be easily recalibrated?

It does well with the 18" but I wonder if it wouldn't be better with smaller wheels. 

Thanks.

It's just an idea that came up.  I will need tire sometime not too far into the future.  It came with the 18 inch wheels and that was OK, but I tend to think that it does make it less stable on bad dirt roads, and to a lesser extent snow and ice.  Now, it's perfectly acceptable on snow and ice, maybe a little less so on some seriously bad dirt road.  Still no real issue. 

It is very high - again, not a real issue.  It would be nicer to have it lowered a little bit - not necessarily a lot.

Recently, my son bought  Jeep Wrangler.  It's basically stock right now and he's figuring out what he wants to do with it for off-road use.  The discussion about wheels has come up and apparently on Jeeps, when tire size in increased, the gas mileage goes down substantially.

So, when I added that last bit of information, it lead to the question of whether I should actually decrease the tire size on my truck.

Another thing I will mention is that when I last bought tires the selection was extremely limited, too.  That may have changed, as I see a lot more vehicles with 18 inch wheels now. 

eta:  Oh the Jeep people say that Jeeps with smaller wheels have more power.

Again, the truck is perfectly fine as it is, but just wondering...

Bhill, it's not a dually and it is a four wheel drive.

If I'm on a deeper dirt, dirt road I have to drive more slowly than I think I should.  I noticed it when I first got it, and have noticed it a couple of times since.  I haven't noticed the issue in ice and snow, really - just on bad dirt roads. It's not a major issue - just a very small one.  I have a very old  f350 (same club cab, four wheel drive, single back wheels) and there is a difference on loose, deep dirt roads. 

You can not use the 16" wheels on a 2005 or newer Ford Superduty. They increased the Brake size in 2005 and increased the wheels to a 17" minimum to fit the larger brakes.

By going with a smaller tire size( overall diameter) you will effectively lower your final drive ratio. Which will give you a little more ummph of the line, but you will run higher RPMs on the highway.  It's a trade off that probably won't improve your overall fuel mileage. But would help if you are having trouble getting loads moving.

If you have squeezed wider tires on your factory rims, That could cause the tires to be a little squirrely in handling. You would have better handling with tires that are spec'd for your OEM 7.5" wheel width. A taller sidewall offers more ability to assorb shocks to the tire (like hitting a rock) than a lower profile tire. But a taller sidewall does give up a little in handling. That's why you see race cars with low profile sidewalls and trucks with taller sidewalls.

For your truck, Better mileage is best achieved with the proper sized tires as spec'd on the door label, Hiway treads will be better than AT tread pattern which are much better than Mud or Floatation tread patterns.

Thanks for the excellent information.  So, I'll stay with what I have and replace the tires when necessary, keeping in mind what I learned in this thread.  I am still running the exact size that came on the truck.  Hopefully, when I change again, there will be more options in 18 truck tires. 

I appreciate the responses.  Thanks!