Front Derailleurs

Mountain Bike Front Derailleur Buyer's Guide

Front derailleurs are amazing devices. One second you're grinding up towards the crest of a hill, and a few seconds later, thanks to a push with your left thumb, you're gaining speed on flat ground, motoring towards a glorious downhill section. Once the necessary speed to graduate to the big ring has been reached, that second thumb push puts a smile on your face and some wind in your sails. Trail riders and cross-country racers know these feelings well, and they owe it all to the front derailleur. A well adjusted, smooth-shifting one will make any ride more enjoyable.

Types

There are two main types of front derailleurs: top pull and bottom pull. They are identifiable by how the shifter cable is routed on the frame to the front derailleur. If the cable comes from underneath the bottom bracket, it is a bottom pull model. If it is routed down the seat tube, a top pull design is required. Most derailleurs are designed to work only with one routing style, but there are such things as dual pull derailleurs capable of working with both top and bottom pull cable routings. There are also two swing types: top swing and bottom swing. Bottom swing designs are the most common and work well on most frame styles. Top swing derailleurs, however, are designed to work with frames that may not allow for proper installation of a bottom swing component.

Sizes

There are two sizes to take into account for front derailleurs: the frame clamp diameter and the compatible gearing ratio.

Front derailleurs come in three frame clamp diameters: 31.8, 34.9 and 38.2mm. This is the measurement of the outside of the frame's seat-tube, and are the most common mounting style. "E-type" and direct mount derailleurs also exist that are secured to the frame by the bottom bracket or with bolts directly to the frame, respectively.

Choosing a derailleur that works with your gearing ratio is equally important. Derailleurs can be designed for either 3x9, 3x10 or 2x10 gears where the first number indicates how many front gears there are, and the second how many rear gears.

Materials

Front derailleurs use steel cages to move the chain from one ring to the other. Many companies use aluminum for the body of their high-end components to save weight.

Things To Look For

There are three things to look for when purchasing a new front derailleur: the cable pull ratio of your current shifter, the number of gears in your drivetrain and the required mounting style for your frame.

There are only two pull ratios, 1:1 and 2:1, which depend on the brand and design of your shifter, so be sure to choose a derailleur that is compatible with your shifter's pull ratio.

The gearing of your bike also determines the style of derailleur you need. Derailleurs are made to work with a specific number of gears, so be sure to select the appropriate component based on these ratios.

The final thing to look into is the mounting style your frame requires, as discussed in the Sizes section.

How Much To Spend

Front derailleurs range in price from $15 to $125. The $15 to $50 range offers all of the available sizes and designs, but the emphasis in this collection is on value rather than performance. Derailleurs between $60 and $125 are top of the line components designed to deliver optimal performance at minimal weight.

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.