Tire size?

The 270X70r22.5 is a popular size for steering axle. It is 3 to 4 inches lower than a 275X80R22.5, a popular tire size. Also a 295X70R225 is almost the same, so close they will run side by side if necessary. The 270X70R22.5 is usually a 16 ply or H rated tire that can carry more weight, another reason they work good on car haulers.

 

Those two are very close to the same diameter. But the 255's aren't up to holding up a steer, they're only rated ~5000#. Carhaulers normally have a 5" drop front axle, not sure what standard axles are.

 

Do yourself a favor and stay away from the smaller tires.
You will thank me when you don't tear up your hood from blowing one of them.
295/75/22.5 or 275/80/22.5 is what you have now I'm guessing?
Like Hammer said the "car haul" axle is like a 5 inch drop.

 

The question I have is WHY you'd want your bumper dragging on the ground? Shipper/receiver/truck stop has a speed bump and you tear it up. Break down and need a tow, you're being charged anywhere from $100 to $400 per hour, and that wrecker driver has to spend time removing the bumper...and then has to find someplace to put it while you're on the hook. Waste of both time and money. Not only that, but those tiny little tires will look ridiculous inside the wheel wells designed for "normal" tires, with a HUGE gap between the tire and fender...but I realize that having a tire "fit" inside the wheel well is a personal preference, so to each his own.

The smaller tires could be problematic due to lower weight ratings, lower speed ratings, and faster rotations at speed which causes more heat and more wear. Your tires, bearings, seals, etc. just won't last as long...leading to increased maintenance costs.

What you're trying to do makes absolutely no sense to me...going to be expensive to do, then will do nothing but increase your cost of ownership and decrease the price somebody else is willing to pay to take it off your hands. If you've got piles of money laying around, have at it. If you're building a "show truck" that won't be pulling many loads, do what you want with it. However, if it's going to be a working truck that you need to depend on to earn a paycheck, do yourself a favor and don't do what you're thinking about doing...it won't end well. Spending a bunch of money to increase your costs has never been a wise business model.

 

Go to the tire websites and look
uo the loaded radius of the tires you have now and potential lower profile tires. The difference in the loaded radius is the actual drop in height you'll see. Make sure to check get at least the weight rating you have now as well.