Rear Derailleurs

Mountain Bike Rear Derailleur Buyer's Guide

Arguably the most notorious component on a mountain bike, the rear derailleur is a triumph of ingenuity. They are complex in appearance, yet simple in function. The harmonious combination of spring, pulleys, parallelogram and cage allow the chain to cycle through up to eleven speeds by simply clicking the right shifter. All derailleurs follow this same recipe, with some minor technical differences. Upgrading a derailleur is a great way to improve shifting performance, reduce weight and enhance the appearance of any ride.

Types

There are two types of derailleurs: 2:1 ratio and 1:1. The numbers represent the amount of cable that is pulled by the shifter over the distance the derailleur moves to change gears. That being said, shifters and derailleurs designed for different ratios are not compatible with one another. It is the manufacturer who decides which ratio they believe works better, and different schools of thought exist on the matter with proponents for both ratios.

Another aspect of derailleurs to look into is the intended riding style. It has become common for companies to produce discipline-specific drivetrains and component groupos at many price levels. This makes choosing the right part even easier for consumers.

Sizes

Derailleurs come in three sizes that depend on the length of the cage. The cage is the section that houses the two pulleys (the part that hangs down vertically). The three cage sizes are short, medium, and long. Shorter cages offer more clearance for rocks and other trail obstacles that could bring a premature end to your derailleur. Short cages are usually used with compact cassettes with a small range of gear sizes. Longer cages can offer slightly smoother shifting, but are more exposed to obstacles. Long cages are usually used with large cassettes or on bikes with three chainrings up front. Regardless of cage length, a derailleur that is compatible with the shifter and cassette will fit in with your drivetrain. If you go from a short cage to a long cage derailleur, you may have to add a link or two to the chain, so as not to over tension it.

Materials

The materials used in a derailleur vary along with its price. Entry-level components use steel and some aluminum. More expensive versions incorporate more aluminum and plastics in order to save weight. Top of the line derailleurs use a combination of carbon fiber, aluminum and sometimes titanium to ensure maximum performance with minimum weight.

Things To Look For

When shopping around for a new derailleur there are only a few technical things that must be compatible with a derailleur in order to ensure proper shifting: the cable pull ratio of the shifter and the number of gears in your drivetrain. There are two standard ratios: 2:1 and 1:1. The ratio of the shifter and derailleur must be the same (these ratios are provided by the manufacturers). Once the possible choices have been narrowed by these requirements, choosing a component rests on riding style, personal taste and budget.

How Much To Spend

Rear derailleurs range in price from $20 to $250.

The $20-$50 range consists of derailleurs with between 7 and 9-speeds with value and dependability being the primary focus.

In the $65-$125 range, 10-speed and 11-speed derailleurs become available, and performance and lightweight materials become more prevalent. Derailleurs in this range use all aluminum and even carbon fiber or plastic parts to save weight.

Derailleurs in the $150-$250 range use only the lightest materials and precision construction techniques to provide unparalleled performance, weight and appearance. Derailleurs in this range may also have a clutch mechanism that helps reduce chainslap and improve shifting performance.

Product Reviews

Before buying, be sure to do your research and read product reviews. Reviews are a great way to find out specifics about a particular model, user impressions, and things to watch out for. After you've purchased a product and had enough time to thoroughly test it, we encourage you to leave a review for other people to see when they are researching bikes and parts on the web.

We hope you've found this information to be helpful. If you have a question that isn't answered in this guide, our mountain bike forums are a great place to get advice from knowledgeable riders. Your local bike shop is also a great resource.