I'll play along, since it's Saturday night and I'm staring at the pager so it doesn't go off.
215/55-16
Facts The Section width of the tire is 215mm, the wheel diameter is 16" and the aspect ratio is 55%. That means, the section height of the tire (or the measurement from the bead to the tread surface) is 55% of the section width.
Note to all following along, the section width is NOT the tread width, but rather the width of the tire at it's widest point. I don't believe this includes any raised lettering, but rather the widest sidewall to sidewall measurement.
So, using the FACT that one inch is 25.4mm we get the diameter of the wheel is the product of 16 and 25.4 or 406.4mm
Using the what we know about the section height listed above, the section height of a 215/55 tire is 225*0.55 = 118.25mm. We also know that you have to multiply this number by two, because each tire, properly inflated, has this section height above and below the wheel.
So the height of a 215/55-16 is the sum of 406.4mm + 118.25mm + 118.25mm or 642.9 mm or in inches, 25.31" in diameter.
Now for the 225/50, since we are mounting on the same wheel, the wheel is still 406.4mm
However, our tire has a section height of 225mm*0.50=
112.5mm.
You can already see that 112.5mm roughly 6mm shorter than 118.25. If you are really anal about this, the difference is 5.75mm
So our properly mounted and inflated 225/50-16 tire will have a diameter of 406.4+112.5+112.5= 631.4mm or 24.85"
Just under 1/2 shorter than the 215/55.
So now that I've done the math, why don't you show us pictures of the two tires in question (same make and model of tire, in the two sizes you list, with a fully visible yard stick or some other measuring device, so we can see you demonstrate your point.
It's only fair, right, I had to show my work, so you show yours, LOL.
TB
