Fixed Gear Skid Marks
The number of skid patches is determined by the given gear ratio and is easy to calculate. Assuming you skid with the same foot forward each time, it is the denominator of the reduced fraction of the gear ratio, starting with the number of chainring teeth as the numerator. In other words, a 48×18 ratio would be 48/18, reduced to 8/3, yielding 3 skid patches. 48×17 doesn’t reduce further, and has 17 skid spots. The rare rider who skids equally often with either foot forward can double their skid patches with ratios that reduce to fractions with odd numbers in both slots.