8N reverse drive

[Jim.ME]

The second one is an AC D14, gasoline. From owning a D14 tractor, I am going to say it has the standard 13.6 - 26 tires. From having operated some of these, I am also going to say the newer ones are likely running 14.9 or 16.9 x 24, 26, or 28" tires, depending on the machine and capacity.

Forklifts are commonly rated for capacity at a 24" load center (for common handling of 48" pallets). Using the load center rating the size of the wheels and tires has been accounted for. Big wheels or little wheels, a little wheel 4000 pound rated forklift has the same capacity has a big wheel 4000 pound forklift.

The biggest differences are the terrain they can safely carry their rated load on and the physical restraints of the operating area needed for the forklift's size. Your small tires warehouse forklift won't be productive on an unpaved site and the RT forklift won't do well in most warehouses.

Edited to correct spelling

 

[Sean in PA]

The length of the tractor matters as well. The stadics factors are not hard to set up. What I was saying is the size of the wheels matter because they factor into how much the leverage the load exerts on the axle pivot point, which must be opposed by leverage produced by the length of the tractor times it's added counterweight.

Notice most of those shown above are large diesel machines designed with modest sized tractor tires, which suggests their manufacturers tended to the wheel size problem I'm talking about.

However the first two are smaller machines, look homemade. The first looks like a Ford 600 series with standard full sized field wheels, I don't think it could lift an 8 foot bunk of lumber off of a truck without tipping when it tried to back away from the truck with the lumber.

The second an International, a diesel with undersized smaller wheels than it came with. It's larger than the 600 and it looks like it would do alright, it could unload an 8 foot bunk, but it wouldn't be able to lift a 16 foot bunk of lumber without tipping forward.

They usually added a lot of ballast weight at the end of the machine opposite the forklift.