OK. So I braved the cold, the snow, the wind, the long hike out to the shed (up hill, both ways) and after moving the lawn fertilizer/seed spreader thingy, the lawn mower, the lawn chairs and digging threw the copper mesh, various parts and a Challenger gas tank and mounting straps, I finally got to my 16" Patriot rims! (The previous garbage was for entertainment purposes only!)
I went looking around to find a good description to help others understand what the heck we would be talking about with Backspacing and Offset and how to measure this stuff. I'm happy to say that I found a very good description of this that even I could understand. It's at Rimz One
. Mike Mashburn, the Pres wrote the article, his lovely wife, Emily, put me in touch with Scott Campbell, Director of Strategic Marketing, who sent me a direct link to the write up so that I didn't have to use second hand sourcing. All nice helpful people! You may want to click on the Home page icon to see what they've got. Added info on OFFSET
16" Patriot steel wheels are 7 1/2" wide, 5.3125 Backspacing and a + 39.75mm offset.
17" Steel Full Size Spare is 7 1/2" wide, 5.375 Backspacing with a + 41.275mm offset
Since back spacing is measured in mm and 1mm = 0.039" let's use +40mm as a standard. And since 1" = 25.4mm, if you want 1" of more backspacing then it's +40 - 25.4 = +14.6mm (+15), the new backspacing.