Is there a difference in size of the wheel wells from the R60 to the F60?

I think the standard wheel size on the R60 started at 17" and the F60 starts at 18".

Thanks. What I was trying to get at is if there was any difference all around for bigger tires. There are threads for the R60 on the biggest tire but not the F60, I'm in the middle of getting certain sizes of a single tire mounted one size at a time then fitting to see which way I'm going.