<font face="Comic Sans MS">The example I used is a 215/75r15.
First number in metric is width of the tire (in MM). Second is aspect ratio. This is the ratio between the width (the first number) sidewall height. If you multiply width (first number) by the decimal version of the second number (in this example, it's .75), you will get the sidewall height from rim to tread.
Now the calculations go like this:
1" = 25.4mm
So, 15" = (15" * 25.4mm/1") = 381mm.
Now take the width (215mm) and do the following:
(215mm *.75) and multiply by 2 (one for each side of the rim), and add the rim width.
215mm *.75= 161.25mm *2 = 322.5mm (plus) 381mm = 703.5mm
To get that back to inches, use:
703.5mm * (1"/25.4mm)
In other words, either multiply by (1/25.4) or divide by 25.4 which does the exact same thing.
So the tire height in this example in inches is approximately 27.697 inches. Keep in mind that the tires typically don't measure exactly as stamped.
And to get the width of the tire is just take the width and multiply by 1/25.4, which ends up being 8.465".
Not only what to do, but how to do it...
On the other hand 205/75r15's are about 8" wide and total height of around 27.1 inches. Keep in mind that they probably won't measure quite that much on the vehicle... [img]/wwwthreads_images/icons/crazy.gif[/img] </font>
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