They don't make tires and axles like they used to! I was talking to an old prospector once, and asked him how the (assembled) Huntington centrifugal roller mills on my gold mine had been moved into place in the late 1940's, from the rail siding about 2 miles away. If you've never seen a Huntington roller mill, I can tell you they are a pile of massive castings that weigh around 6 tons when assembled.
He replied, "Oh, they used that old 1929 Ford AA (single rear wheels) tray truck, that is a now a stripped wreck over there!"
I said, "But the AA Ford truck is only a 1-ton truck! - and it has wooden-spoked wheels! You mean to tell me they put 6 ton roller mills on a 1 ton truck with wooden wheels, to haul the mills in here?!"
"Yep", he replied. "But when I saw those back tires on the AA Ford, with the roller mill on there, I was sure they was gonna bust!!! But they made it!!"
I guess the fact they only had to go 2 miles, and they probably only travelled at walking pace was the reason they made it.
Regardless, imagine sitting 6 tons on one of todays 1-tonners? The rear axle would buckle within a minute.
https://www.flickr.com/photos/42220226@N07/44829708091