Hi Mike,
I would normally post a good internet site, though just rebuilt my PC (diff story) and not re-imported my bookmarks yet.
Here it is manually:
With an aspect ratio of 75% of the width (285):
75% of 285mm is 213.75.
213.75 x 2 = 427.5
For "427.5 in inches", Google says 427.5 millimeters = 16.8307087 inches
On a 16" rim, 16 + 16.8 = almost 33" (1/4" short)
It's just a touch under 33", same equivalent size basically.
Though I bet if you measure the diameter of the 33 tyes, they're not exact anyway.