Ouch... Wheels don't fit...

[FETorino]

Originally Posted by BBC71Nova

THEY DON'T FIT! . I had thought and was led to believe that using a wheel with known size and backspace was best method of determining what size new wheels to get.

I have a set of 15" X 10" wheels with tires mounted. The wheel is listed as a 5" backspace wheel. That setup fits fine but could stand to be 1/8" further inboard.

With the new setup I went with an 18" X 11" wheel. Simple, right. Split the 1" difference in width yielding 5.5" backspace plus the extra 1/8" and voila new wheel needs to have 5 5/8th backspace to fit perfectly. NOPE. Apparently not.

I'm not sure I follow your logic here. If 5" bs is fine but it could be 1/8" more inboard then you want 5.125" bs. If you go from a 10 to an 11" width the BS doesn't change you still have only the 5.125" to work with inboard. The question is with the 10" wheel did you have the extra .875" outboard to allow for the wider width wheel? You didn't say but from your measurements I would guarantee that the wheel is hitting the tubs cuz you have .5" to much BS.