Fun fact about bike wheels

Bike wheels come in two main flavors for road bikes: 27 inches and 700c. I've been putting together my project bike and I bought a new rear wheel. I tried to put my 27 inch tire and tube on the back, and it was too big. So then I went to google and searched for 27 inches in millimeters and discovered that 27 inches = 685.8 millimeters, and thus my tire was not a 700c, right? Wrong. 27 inches is an inner diameter measure. 700c was originally an outer-diameter measure of .7 meters, but has since changed and has almost no relation to 700 anything.

So, for bike tires, 700 millimeter tires are smaller than 27 inch (685 mm) tires.

Now you know, and knowing is half the battle.