Spent a nice saturday afternoon with alschnertz talkin' Volvos and drooling over his one owner (father to son, one family I guess is more accurate) 1968 Amazon Estate In BRG with a camel interior and admiring his 140 wagon and 544. I was there to pick up a full set (5) of 4 1/2" wheels dated '63. He was letting them go for what I thought was a very reasonable price. Right now they are sort of battleship grey but will be refinished, either with paint or powdercoating in something resembling volvo silver, then topped off with nos caps and beauty rims. That's pretty much decided. What isn't decided is which tires to buy, but more importantly what size tire is best. I know I've asked this before and since then I have done some research and have concluded, as did al, that a 185 was probably as wide a tire as could reasonably be put on a 4 1/2" rim. I also know that many have put bigger tires on and I actually have 195's on her now but that's beside the point.

So can anyone translate for me what 185 to get? IOW what 185 tire size would give me about the same overall diameter that the stock 6.40-15(referencing my old wagon's owners manual and roughly translates to a 165 80R15) had?

Mental laziness on my part but math was really not my thing. Thanks in advance.