The smallest category for our little racers of tomorrow. These 12 inch wheels are perfect for soap boxes. Quality cycling wheels from Taylor Wheels. Most bicyclist begin riding at some point in their childhood with a 12” bicycle. The right 12” bike is then needed. Whereas the large 12” ( 12.5” or 12 1/2”) is only an approximate diameter size of the outside of the tyres. You can get the exact size of the wheel or tyre through the ETRTO- Dimension. The inside diameter of the tyre as well as the tyre width in millimeters. At Taylor Wheels you will find 12” bike wheels with the inside measurement of 203mm. This designation you will find on the side of your tyre wall. The most widely used size is presumably 47-203 (12 1/2 x 1.75).