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I got to wondering about this (you know, "things that make you go hmmmmm?)....
What could possibly be the reason that tire manufacturers use the goofy formula of width x ratio = height? I mean, comeon, there's dozens of threads here on IMBOC alone, where people are either asking explanation of tire sizes, or are getting corrected due to incorrect math.
So why didn't they simply make the second number the actual height, instead of making you do the math?
Is this a conspiracy, to give the sleeveless guy at Discount the power to decipher tire sizes faster than the Average Joe, giving him Superior Intellect?
Or is there possibly a legit reasoning behind the goofy formula that I've not thought of?
 

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Hey, at least it's not some bizarre alpha-numeric system! At least this way we can do the math to get the sidewall height. I mean, what the heck is a G70-15?! :smile:
 

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Any system used would require a knowledge of math and what the numbers represent. Look at the OEM Bullitt tire size: 245/45/17

Ok, first off, tires are sold worldwide so do the manufacturers label by English or metric units? We could go metric and remember that 25.4 mm equals 1 inch, but this is America so we want inches, screw the French. Let the rest of the world do the conversion from inches to metric. So 245/45/17 becomes 9.6457/45/17. But the aspect ratio (profile) is confusing so we want a measure of tire height. Do we use the section height, 4.3406 inches? Now we have a 9.6457/4.3406/17 tire designation. Or do we double the section height to account for the top and botton of the tire section, giving us a 9.6457/8.6812/17 tire? Or do we add in the rim OD to the doubled section height to give a final OD of the mounted tire? That would give us a 9.6457/25.6812/17 tire designation. How many more people would have any concept of what a 9.6457/25.6812/17 tire designation would represent versus 245/45/17?

I think I'll vote to stick with 245/45/17.
 
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