there's race wheels in 5.5, 5.75 & 6.0 widths. The 6.0" width fits the 190/50 section tyre better and should have no probs fitting in. I'm guessing that a 5.5" wheel weighs less than a 6.0" wheel and subsequently, probably, a 180 section tyre weighs less than a 190 section tyre. So there must be a trade off somewhere between weight and contact patch but I don't have the money to find out
The race 916 used 19/67 race tyre which equates to 190/60 section tyre but not sure what rim width it was on. Seem to remember Shazaam talking all about this before.