Bicycle riders are sometimes challenged by the steep elevation of public roads in mountainous areas. Cyclists participating in a group tour that covers steep road terrains can improve the gear ratio of their bicycle by replacing their original rear-wheel cassette.

The rear-wheel cassette of a road bike contains several sprockets of different sizes that rotate the wheel when propelled by the chain. The original cassette on most road bikes is designed to accommodate the majority of routine hill elevations. However, some group tours are routed through particular sections of road that are exceptionally steep.

When climbing a hill, a bike rider appears to be pedaling fast while actually moving rather slowly. For hills that are especially steep, the lowest gear on your bicycle may simply be inadequate. After installing larger sprockets on the cassette, you are likely to experience the steeper portions of a mountainous tour as less daunting.

Gear ratios

Sprocket size determines the ratio between pedal revolutions and wheel revolutions. On level terrain, a smaller rear sprocket is adequate to easily move your bike along faster. On a steep hill, a larger rear sprocket becomes necessary, requiring more pedal revolutions. Replacing your cassette effectively results in the addition of one or more lower gears.

Cassette removal and dismantling

Rear-wheel cassettes are typically replaced in their entirety. Although the smaller sprockets can be removed individually, the larger sprockets are usually bonded together on the cassette. Removal of the cassette from the wheel requires a special tool referred to as a chain whip.

If necessary, two chain whips can be used together to remove the smaller sprockets from a cassette. The second chain whip is needed to turn the smaller sprocket counterclockwise, while the remainder of the cassette is held steady with the other chain whip. When reinstalled on a bicycle, the complete cassette is on the right side and is pulled clockwise by the chain. The clockwise pulling motion keeps the cassette sprockets tightened.

Related adjustments

Your bicycle chain is always held fairly taut by the derailleur, which is the arm underneath the cassette that moves the chain from sprocket to sprocket. The use of a larger sprocket may require an adjustment of the derailleur. If your derailleur cannot accommodate a larger sprocket, you may need a slightly longer chain.

Steep climbing on a mountainous road is inspiring, but touring with a group is possibly a temporary activity. Many cyclists who replace a rear-wheel cassette for a specific bike ride often have their original cassette reinstalled after the event. Contact a bicycle shop such as Sarasota Cyclery Inc for more information about bicycle repairs.