15x8 w/3.75" backspace question

Maybe you can help blue.
I'm having trouble finding 431.8mm tires for my truck, 45.72 centimeter wheels for my BMW, and 508mm tires for my camaro. Where should I look?
I know where I can get 390s for my fox, I just don't want to spend that much.....

Cute. But tire width is already listed in mm’s as the standard. As is offset. Pretty much all 5x4.5” pattern wheels are cross listed as 5x114.3mm. So diameter and width are still inches, so what? But are they really?

Have you checked to make sure those 18’s on your Beemer are 18.000”? Like, there’s no chance at all that they’re 17.992’s right? Or, you know 457mm :p

It’s moot what you call it anyway, all the machines that make that stuff are digital and can read out and reference in either set of units. We all just take for granted that 18’s are actually 18’s, and if we actually measure them it’s with a tape measure that sure as hell can’t pull off a reading down to .008”. Soooooo