Re: Holsclaw and 9" wheels/tires
That size is rare but not impossible to find. They were far more common in the 40's and 50's. Duro and Towmaster both still make the tire. Figure on about $55 each plus shipping. Some farm tire dealers might still keep them as might some motorcycle shops that deal in bike trailers. I've had a few older Holsclaw bike trailers with them on it.
They are still somewhat common overseas. I've seen various lug patterns and several type of rims, especially foreign made wheels. I've seen a few alloy two piece rims which bolt together in two halves, and a few monohub rims.
If you walk into a tire dealer, if they even try to look it up, most will assume it to be an industrial tire or fork lift size.
I have also seen a few really old pop up campers with that size tire.
The tire is also used on a few older, larger riding mowers as front wheels as well. I have a set on a super duty handtruck I built years ago after converting a boat trailer over to a more common size.
I have one boat trailer here now with them, a single axle Dilks trailer, with 5 lugs on each wheel. The bearings are standard 1" on this one, but I've seen some odd bearings as well.
From what I can see of your trailer, Holsclaw doesn't particularly come to mind. Is there any reason you think it might be made by them?
There were many trailer companies over the years, it's often nearly impossible to determine the maker of a particular trailer without some sort of badge or plate. It could also be completely homemade as well.
They most likely chose the smallest tire size which could handle the weight.
What type of suspension does it have? Any numbers or tags on the frame?