Thanks that's exactly what I needed to know and meant by dished center

, except the fact that 17' is as far as you'll go on a dished/concaved center with a fat lip rim, no chance of making them in 18s or 19. Is the limiting factor that with the larger diameter sizes that the taper of the spokes continues too much where it meets the rim exaggerating the backspace limitations ? Hope that ,makes sense

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A Fontana dish on a 17 Fat lip would be nice and a standard rim 18 if possible.
Just to clarify something are Fat lip wheel centers a full inch larger in diameter than a standard wheel center of the same size outer diameter ?