How bicycle gears are measured…
Bicycle gear calculations are based on the distance, in metres, that a bicycle travels for each turn of the pedals. This distance is commonly called 'metres development' – a rather odd name for a logical and useful way of measuring gears.
Low gears will move your bike a very short distance for each turn of the pedals – just what you need for tackling steep inclines at slow speed.
High gears will move you three or even four times as far – assistance from gravity or a tail wind will probably be needed!
For practical purposes, the extremes are:
- 2 metres : lowest gear
- 9 metres : highest gear
Unless you are riding a folding bike (I do!), the circumference of your wheels will be just over two metres. Later, I'll help you measure tyre circumference – accurately and without tears – but for now we'll assume that our bicycles roll forward 2.1 metres for each wheel rotation. |