Ahh but I believe you have it wrong Montoya32.
275 is the measurement of the width of the tire in mm and is not the height at all.
To calculate the height you use the other numbers.
Example Tire size 275-60-20
This means the width of the tire is 275 mm or 10.83 inches wide
The 60 means that the sidewall (black part from the rim to the of the tire thread) of the tire is 60% of the width of the tire.
Doing the math 60% of 275 mm or 10.83 inches is 165 mm or 6.50 inches respectively.
Now looking at the tire from top to bottom, you have a sidewall, then rim, then another sidewall.
So that gives you 6.5 + 20 + 6.5 where 20 is the size of the rim.
That comes up to an even 33 inches give or take.
Applying the same logic to the factory tire: 265-65-18
65% of 265 = 172.25 mm or 6.78 inches of sidewall.
Adding that to 18 inch wheel gives you 2(6.7
+ 18 = 31.56 inches tall tire give or take a few hundredths of an inch depending on the tire manufacturer.
Hope that clears the air for you.