According to the tire size calculators there should be about 0.30" height difference.

Right.

 

both brand new tires?

inflated same amount?

I'm reaching here, but yeah the calculator I used says a .46" difference, which is still way less than what your pic shows.

weird.

 

yeah - .46 for me too. so what is the difference - it looks like more. But depending on how close the camera is the bigger the gap looks. exactly how much difference is there? maybe take a pic with a ruler.

 

are the tires leaning are you sure of the side wall heights and inflation thats a huge difference dam.

 

i thought about it and it makes sense the rim is 3 inches taller, and the side wall only 15 mm shorter so the total height of the tire will be about 2.5 inches taller. If i lost you il break it down some more jsut rims the wheel is 3 inches taller. the tires have a side wall of 30 mm for the20 and 45 for 17.the sidewallfor the 17 would have tomake up that 3 inch difference to be equal the calcis wrong, 3 in sidewall is 75 mm about. Thats why there is the gap. if you guys need any more ill do stupid 5th grage math, thus i am smarterthen a 5th grader

 

if you plug the two sizes in HERE it tells you that the 20" wheel will have a .46(inch) taller stance than the 17"

 

225/30/20 wouuld be the ideal size

 

something not right there I would fit 245/25/20
http://www.miata.net/garage/tirecalc.html

 

i get a difference of 1.4 inches when i did it, running 17 to 20

 

245/30/20 = 25.8 inches tall
235/25/17 = 25.3 inches tall

now there is some math for a 5th grader