Wheel spacers, doesn't make sense??? Options

[retrotech]

Help.
I have been on this topic prior to fitting wheels, but the numbers don't make sense. I am using 17 x 7" 993 wheels with marked off set of 55mm. I have 205 tires mounted. I want to use 215, but everyone says they won't fit.
From the beginning I thought I would need 23mm spacers, but I just tried some 1/4" spacers that were laying around and they work.
On the front with 1/4" there is slight rub on full lock, at front of tire, with 1/2" none.
On the rear with 1/4" there is a closer fit 1/4 - 3/8" at the top inside, with tons by the fender lip, that has been rolled.
With 1/2", just the reverse as above. It almost looks like I could use 215's. But how can this work with only 1/4 & 1/2" spacers.
Anyone with a similar application to advise on there spacer size?

Retro

[Mueller]

55mm - 6.5mm = 48.5mm which is approx. what the 15x7 "R" rims are...(49mm I believe)

35mm offset (for a 7" rim) is what Revolution sells which fits under the stock fender.

the front can take a rim with less offset, that is why the 12.7mm spacer works better....you could get away with an even thicker spacer in the front if you want to.....

23mm is not the correct offset for 7" wide rims under stock fenders

for comparison, when I had the "ricer" rims mounted to my car, they have a 40mm offset and with a 205 tire, they fit perfect in the rear