What does a derailleur do?

Asked by: Sean Ramirez

A derailleur is a variable-ratio bicycle gearing system consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another.

How does a derailleur work?

They are used to correctly adjust the shifting between cogs on threading or turning the barrel adjuster counterclockwise effectively shortens the cable.

Do all bikes have derailleurs?

Most modern bikes are equipped with a derailleur gearing system – stay with me, we’ll get to the terminology – where the chain runs between many different cogs.

What are derailleurs on a bike?

The derailleur is the device that changes gears by moving the chain from one sprocket to another. There are two derailleurs: one on the rear and one on the front. The highest ratio (when the bike can go fastest) is produced when the chain is on the biggest sprocket in the front and the smallest in back.

What does a derailleur hanger do?

What is the purpose of derailleur hanger? Bicycle rear derailleur hanger is designed with purpose to break or bend in order to prevent or limit damage to bicycle frame or other drivetrain components in case of accident: crash, drivetrain failure an others.

When should I replace my derailleur?

Derailleurs will last almost indefinitely. The jockey wheels will wear out in time (tens of thousands of km) but the rest of the mechanism shouldn’t see significant wear. It could be that the spring will break at some point due to material fatigue, but that is also a relatively easy to replace part on most derailleurs.

How do you use a derailleur gear?

Left hand: Controls the front gears/front derailleur by moving the chain up and down the chain rings. These levers cause big jumps in gears for sudden changes in terrain. Right hand: Controls the rear gears/rear derailleur by moving the chain up and down the cassette.

Can you ride a bike without front derailleur?

Are Front Derailleurs Necessary? These days front derailleurs are essentially not necessary, on mountain bikes at least. Now even high-end road bikes are starting to lose their front derailleurs. With a larger rear cassette, it’s possible to get the same number of gears without the need for a front derailleur.

Why are bikes sold with only one gear in front?

Q: Why bikes are being sold with only one gear in front? These bikes are called 1X or OneBY drivelines. They have only a single chainring and a wider ratio rear cassette. Their advantage is that they don’t have a front derailleur or shifter.

What gear should I use on a flat road?

High Gear. This one is great for descending, accelerating, or for use when you want to go nice and fast on a flat road. In a high gear, you travel a long way for each turn of the pedal.

Is a derailleur hanger necessary?

Carrying a spare derailleur hanger will help you when you’re at a loose end. You wouldn’t think a derailleur hanger would be such a crucial and essential part on a bike. Not many people know how important they actually are, but they help protect your bike frame from being damaged by snapping.

Do all derailleurs need a hanger?

Currently, SRAM does not offer any direct mount rear derailleurs, and always need to be mounted to a standard derailleur hanger. If your frame has a direct mount hanger, and you are switching from Shimano direct mount to SRAM, you will need to replace your hanger with a standard mount version of your hanger.

Why does a derailleur break?

If your chain is too long, and you are in the ‘small-small’ combination, it is possible for the derailleur to sort of fold up on itself. Flip your bike over and put it in the smallest gear up front and the smallest gear in the rear and make sure the chain isn’t rubbing on the derailleur.

How much is a new derailleur?

There can be a range of prices for replacement derailleurs, starting around $20 and going all the way up to $700.

Can you fix a broken derailleur?

Some problems can be repaired trailside while others require parts and tools most riders don’t commonly carry. Your bike’s drivetrain is really a simple system, and if you know what to look for, you can easily repair your derailleur yourself.