Biggest Sized Tire On These Rims

[Speedy1210]

What's the biggest size tire I can fit on these rims?

 

[Mustang Bob]

What size rim is it 18?19?20? 9 inch 9.5 inch 10 inch?
I have been told that with the rims I have which look very similar, my rims are 19X9.5, I can go as wide as 275/40R.
Currently I am running 255X40R19

 

[1 Alibi 2]

What size are the rims ? ( dia. & width )