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.

What does a derailleur do on a bike?

The rear derailleur is the mechanism that shifts the chain at the rear sprockets. There are many different models but they all share the same basic design and functionality. Derailleurs are secured to the bike with a mounting bolt to the frame's derailleur hanger.

Does every bike have a derailleur?

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.

How much does it cost to fix a derailleur?

If you take your MTB into a local bike shop the average price to replace a rear derailleur is going to be $110. If you DIY replacing a derailleur will cost about $50 (plus your time) This price will depend a lot on the actual derailleur needed. Usually a bike shop will also take care of other problems.

Can you use a bike without a front derailleur?

These days front derailleurs are essentially not necessary, on mountain bikes at least. ... With a larger rear cassette, it's possible to get the same number of gears without the need for a front derailleur. Therefore the arguments that a lack of derailleur means less range are no longer valid.

How a Rear Derailleur Works

Is it hard to install a derailleur?

It's relatively easy, and if you haven't done it before, you'll learn the procedure of tuning a rear derailleur <i>from scratch</i>, which can be invaluable out on the trail. Are you planning on installing a new cable? It's not required, but this would be the time to do it. If so, you'll need cable cutters.

Can you ride a mountain bike without a derailleur?

Technically, a mountain bike can work without a derailleur. If your derailleur stops working, you can rig it to keep the bike working. However, you also have the option to ditch it completely and make it a single speed, if you wish.

Are derailleurs universal?

A derailleur for your mountain bike should match the specifications on the original derailleur. That is, while it doesn't need to be the same model of derailleur, it does need to be the same brand, in almost every case. It also needs to match the number of gears, or have more intended.

Do derailleurs wear out?

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.

Do derailleurs have speeds?

The spacing between 9 speed and 10 speed is controlled at the shift lever. A 10 speed rear dérailleur will work with a 9 or 10 speed cassette and shifter. A 9 speed rear dérailleur is not compatible with 10 speed. The width of the chain and the cogs is the biggest issue.

What is front derailleur?

The front derailleur is the mechanism that shifts the chain on bike with more than one front chainring. There are many different makes and models, but they all share the same basic design and functionality. Front derailleurs are attached to the bike with either a clamp or bracket.

Why do you need a derailleur?

A rear derailleur (often referred to as a 'rear mech') is the mechanism that moves the chain from cog-to-cog on the cassette at the rear of the bike. ... You need to ensure it's compatible with the rest of your bike's components and in good shape.

Can you put a derailleur on a single speed?

The installation of the derailleur will necessitate the purchase of a special hanger which puts the derailleur in a position from which it can encompass all rear cogs. Most dedicated single-speed frames do not have a built-in derailleur hanger or special bosses where you can install one.

Why does my derailleur keep breaking?

This can be the result of a crash, mis-shift or most usually simply being in the wrong gear when the chain and derailleur are under the most load either when the road goes upwards sharply or setting off from a standing/stationary start.

Can I replace my own derailleur?

Believe it or not, it's not difficult to replace the rear derailleur yourself. Before replacing a "bent derailleur" make sure it's not just the derailleur hanger! ... If you can't (or don't want to) remove the idler pulley from your new derailleur, you'll need to break the chain. See our section on chain repair.

How do you take off a bike chain without a chain tool?

Take a punch tool and place it over one of the rivets in the chain. Use a hammer to push the rivet out and separate the chain to remove it. This method can also be used to shorten a new chain if necessary.