Gearing Up

If your biking experience goes back as far as ours does, to when you climbed onto a tricycle for the first time and pedaled off to conquer the world, you may remember what it was like to ride with one gear. Cruising down the sidewalk at your parent’s side was pretty easy — at least until it started sloping uphill. You had to apply more and more force to keep your bike moving, until finally your little legs gave out and your parents had to turn around to head home.

Why was riding a tricycle uphill an impossible task? When a bicycle has no gears, each time you rotate the pedals, the rear wheel also rotates one turn. You rotation of your pedals will move your wheel one rotation (the full cir­cumference of that wheel.) The force required to move that one rotation is much greater if you’re pedaling uphill. The idea behind gears is that the dis­tance the wheel travels for each rotation of the pedals can be lengthened or shortened, allowing you to apply a consistent amount of force, regardless of whether you’re on an incline or decline.

Gears rely on the combination of the size of the front chainrings and the sprockets on the rear wheel of a bike. By switching between different sizes of chainrings and sprockets, gears allow you to use the same amount of

force when pedaling, regardless of the terrain. Most bikes have two or three chainrings with 22 to 52 teeth between the largest and smallest chainring.

On the rear cluster of sprockets, they have 11 to 32 teeth. Based on where the chain sits on the chainrings and sprockets, the rotation of the pedals will cause the rear wheel to have a different number of rotations.

For example, if the chain sits on a chainring with 44 teeth and a sprocket with 11 teeth, the gear ratio is 4 (44 * 11), which means that, for every rota­tion of the chainring, the rear wheel will rotate 4 times. A higher ratio is ideal for going downhill or pedaling with the wind at your back. If the chain is on a chainring with 22 teeth and a sprocket with 32 teeth, the ratio is 0.69 (22 * 32). A low ratio such as this is needed for climbing up a steep hill. (Is your head spinning as fast as your gears yet?)

The total number of gears on a bike is calculated by multiplying the number of chainrings by the number of sprockets. If your bike has 3 chainrings and 9 sprockets, you’re riding a 27-speed bike. On a bike with more gears, you’ll have a wider range of lower gears for going uphill and higher gears for going downhill. This also makes the changes in gear ratios much smaller, allowing you to more easily find a comfortable gear in which to pedal. Dennis’s tour­ing bike has 27 gears and gives him great flexibility whether he’s huffing and puffing going up the side of a mountain or screaming down the other side at 50 mph.

When you’re buying a bike, keep in mind the following gear tips:

✓ Choose a bike that has high enough gears to support faster speeds with­out your legs spinning at an uncontrollably fast number of revolutions.

✓ Choose a bike that has low enough gears to enable you to climb hills.

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