Rear Derailleur – Definition & Detailed Explanation – Bicycle Components Glossary

I. What is a Rear Derailleur?

A rear derailleur is a key component of a bicycle’s drivetrain system that is responsible for moving the chain across the different gears on the rear cassette. It is a mechanical device that is attached to the rear dropout of the frame and is controlled by the rider through the shifters on the handlebars. The rear derailleur plays a crucial role in determining the bike’s gear ratio, which affects the speed and efficiency of pedaling.

II. How does a Rear Derailleur work?

The rear derailleur works by using a system of springs, pulleys, and cables to move the chain from one gear to another on the rear cassette. When the rider shifts gears using the shifters, the derailleur moves laterally, guiding the chain onto a different sprocket. The tension in the derailleur’s springs keeps the chain in place and ensures smooth shifting between gears. The pulleys on the derailleur help to maintain tension in the chain and keep it aligned with the sprockets.

III. What are the different types of Rear Derailleurs?

There are several different types of rear derailleurs available on the market, each designed for specific types of bikes and riding styles. Some common types include:
– Road rear derailleurs: These are designed for road bikes and have a more compact design for smoother shifting on paved surfaces.
– Mountain bike rear derailleurs: These are built to withstand rough terrain and have a longer cage to accommodate larger gear ranges.
– Gravel bike rear derailleurs: These are a hybrid between road and mountain bike derailleurs, designed for off-road and mixed-terrain riding.

IV. How to adjust a Rear Derailleur?

Adjusting a rear derailleur is a crucial maintenance task that ensures smooth and precise shifting. To adjust a rear derailleur, follow these steps:
1. Shift the chain onto the smallest sprocket on the rear cassette.
2. Loosen the cable tension by turning the barrel adjuster on the derailleur or the shifter.
3. Align the derailleur hanger so that the pulleys are parallel to the sprockets.
4. Adjust the high and low limit screws to prevent the chain from falling off the cassette.
5. Increase the cable tension by turning the barrel adjuster until the chain shifts smoothly across all gears.

V. What are common issues with Rear Derailleurs and how to fix them?

Some common issues with rear derailleurs include:
– Chain skipping or slipping: This can be caused by a worn chain or cassette, misaligned derailleur hanger, or cable tension issues. To fix this, replace the chain and cassette, realign the derailleur hanger, or adjust the cable tension.
– Poor shifting: This can be caused by cable stretch, worn pulleys, or dirty components. To fix this, replace the cables, pulleys, or clean and lubricate the derailleur.
– Bent derailleur hanger: This can cause shifting problems and should be straightened or replaced to ensure proper alignment.

VI. How to choose the right Rear Derailleur for your bike?

When choosing a rear derailleur for your bike, consider the following factors:
– Compatibility: Make sure the derailleur is compatible with your bike’s drivetrain system, including the number of speeds and gear ratios.
– Riding style: Choose a derailleur that is suited to your riding style, whether it be road cycling, mountain biking, or gravel riding.
– Weight: Consider the weight of the derailleur, as lighter options may improve performance but could be less durable.
– Budget: Determine your budget and choose a derailleur that offers the best value for your money.

Overall, the rear derailleur is a crucial component of a bike’s drivetrain system that plays a significant role in shifting gears and determining the bike’s performance. By understanding how it works, how to adjust it, and how to choose the right one for your bike, you can ensure smooth and efficient riding experiences.