Originally Posted by
IGH_Only
Thanks, I understood the 622 but I've never seen the formula before and wasn't sure how to calculate how much tire part would add to it.
Tire width and tire height aren't the same thing... tires aren't cylinders. The same tire will have different dimensions when mounted on different rims. Different tires of the same nominal size will have different dimensions when mounted on the same rim. Many tires will not match their nominal dimensions when mounted on any rim.
To get the exact diameter by calculation, you'd need to measure the height of that tire, when mounted and inflated on that rim... at which point you could just measure the wheel diameter directly and skip the math.
What I'm not grokking is what you'd actually need the number for. The only reason I can come up with would be to calculate the circumference, to calibrate a magnetic-sensor bike computer, but that's always been in millimeters?
--Shannon