Beginner's Guide: Detailed Explanation of Front Derailleur Types, Installation, and Compatibility
Many road bikes, dirt bikes, and even e-bikes depend on the front derailleur as a crucial part. Its primary task sounds really simple—moving the chain between chainrings. Don't undervalue it, though; the front derailleur performs more than first seems possible.
More riders are choosing 1x configurations these days; hence the front chainring only exists once. The question then is: in this arrangement, what part does the front derailleur play?
What Is a Front Derailleur?
Early in the 20th century, the front derailleur first emerged, and its name fairly sums up its purpose—shifting the chain from one chainring to another. The front derailleur is a quite basic drivetrain component when compared to the rear derailleur. Whereas the front derailleur only interacts with the chain during shifting and stays out of the way the rest of the time, the rear derailleur must control shifting over several cogs on the cassette and maintain chain tension.
Though less complicated than the rear derailleur, the front derailleur comes in a variety of shapes, each accomplishing the same goal in somewhat different ways.
What About 1x Systems?
Many mountain bikes and gravel bikes these days are adopting 1x systems—single chainring configurations combined with a wide-range cassette that provide gear ratios comparable to those of multi-chainring configurations.
The main advantage is you can cut out the front derailleur completely. A 1x drivetrain theoretically streamlines things, lowers the risk of mechanical problems, removes the complexity of front derailleur setup, minimizes clogging with mud, and even helps to somewhat offset weight.
Most 1x chainrings have a narrow-width tooth design, which meshes well with the chain and greatly lowers the chance of dropping it. Install a chain guide on the frame for extra security to bring even more peace of mind. Back derailleurs in 1x configurations usually have a clutch mechanism to assist in chain stability.
Nowadays, off-road bikes go with 1x drives; some road riders are beginning to value their simplicity. That said, the trade-off is more significant gear changes that could throw off your rhythm on a road ride.
Front Derailleur Installation: Direct Mount vs Clamp-On?
Mount a front derailleur on a bike mostly in two methods.
Among the more often used kinds are clamp-on front derailleurs. They have a hinged clamp secured with a bolt that hooks straight to the seat tube. Should you have to change the position, you may easily release the bolt and slide the derailleur up or down. Though most include additional shims to match typical widths like 34.9mm, 31.8mm, and 28.6mm, clamp-on front derailleurs are available in several sizes to meet different seat tube diameters.
Attached right to a bracket on the bike frame, direct-mount front derailleurs are Typically, screws or rivets fasten this bracket. Loosening the bolt and sliding it up or down on the mount will help you to change the derailleur's height.
Separate clamp adapters are typically sold to make your front derailleur compatible even if it is a direct-mount type and you want to put it on a frame built for clamp-on derailleurs.
How Does a Front Derailleur Work?
Comprising two long plates known as guide plates, which sit on either side of the chain and are joined at the top and bottom, the front derailleur is
If it's positioned correctly most of the time, the guide plates won't touch the chain unless you're shifting. Attached to a pair of lever arms set atop the bike frame are these plates. The shifter in mechanical shifting systems pulls a wire attached to the derailleur via an actuator arm extending from the side of the derailleur, therefore moving the derailleur.
Usually, the left shifter handles the front derailleur and the right shifter the rear derailleur. Electronic groupsets let one personalize this arrangement. For instance, SRAM eTap AXS pushes both shifters simultaneously to default as front derailleur control.
Pulling the shifter tightens the cable and drives the guide plates outward. This movement features less up-and-down action because of a well-designed structure. The plates move, pushing the chain from the smaller chainring to the larger one. The derailleur disengages after the chain sets on the next ring, allowing you to ride without incident until your next shift.
The derailleur contains a spring. The spring pulls the derailleur inward when you release the shifter cable, therefore shifting the chain from the bigger chainring back to the smaller one.
To change gears, keep pedaling, as the chain under tension is what is being moved. You might have to relax your pedaling force slightly for better shifting—especially when switching to a bigger chainring.
Front Derailleur Limit Screws
Just like the rear derailleur, the front derailleur also has "high" and "low" limit screws that control how far it can move at either end of its range.
These screws, marked with "H" (for high) and "L" (for low), are built into the derailleur body. They let you fine-tune how far the derailleur can shift inward or outward. The "L" screw sets the limit for inward travel, while the "H" screw controls the outward travel.
Limit screws play a crucial role in preventing the chain from falling off, making them an essential part of learning how to adjust your bike's shifting properly.
Electronic Groupset
Apart from cable-actuated shifting, electronic shifting is the most often used alternative available presently. Motors move the front derailleur in systems such as Campagnolo Super Record Wireless, SRAM Red AXS, and Shimano Dura-Ace Di2 R9200.
Strong motors included in electronic front derailleurs let you shift under load. Still, this strains the bike frame, more specifically on the front derailleur mount. SRAM AXS front derailleurs feature an extra support block built in the box to solve this.
Chainring Design
Modern chainrings are meticulously crafted to run effortlessly with front derailleurs, therefore guaranteeing better shifting. Along with varied tooth forms across different sections of the ring, large chainrings can have ramps and small metal pins to enable the chain to slide up from the smaller chainring more readily.
Since the chain just lowers down, it is really easy to switch from the big chainring to the smaller one. Moving from the smaller chainring to the bigger one is more difficult, though. Designed with an "overshift," front derailleurs push the chain somewhat further to the right before settling it back into place once the shift is over. This overshift technique also finds use in electronic shifting systems.
Front Derailleur Trim
Your rear derailleur modulates the chain's angle between the cassette and chainrings. Using some gear combinations, such as the largest cog on the cassette matched with the largest chainring, this angle—known as the "chainline"—can get extreme. Under these circumstances, the chain may scrape against the guide plates of the front derailleur, producing a displeasing noise as you ride.
Many front derailleurs enable you gently nudge the guide plates slightly to one side without actually changing the chain between chainrings to correct this. As long as the front derailleur is set up correctly, this trimming function helps keep the drivetrain quiet and free-running.
The "yaw" design of SRAM's mechanical front derailleurs causes the guide plates to revolve somewhat around a vertical axis. Without a trim feature, this helps stop chain rubbing. To operate at its optimum, this design, meanwhile, calls for extremely exact setup.
Electronic shifting systems take care of trimming automatically, therefore maintaining the drivetrain free from rubbing, as long as the height and angle of the front derailleur are properly adjusted.
Cable Routing
Cable routing refers to the direction in which the derailleur cable is pulled, and it depends on the frame design and how the cables are routed.
Top Pull: This setup routes the cable from the top tube down to the front derailleur.
Bottom Pull: In this case, the cable runs along the down tube and passes under the bottom bracket to reach the derailleur.
Dual Pull: A more versatile solution, dual-pull front derailleurs can accept cable routing from either the top or bottom, making them compatible with a wider range of frame designs.
Front Derailleur Compatibility
Front derailleurs made for triple chainrings cannot be swapped out for those made for double chainrings. Their guide plates are sized and shaped to accommodate particular chainring configurations.
Divergent brand derailleurs are not always compatible with one another. Like rear derailleurs, they frequently use variable cable pull ratios; hence the guide plates will move varying distances when you shift. This variance can occur between earlier and newer models from the same brand, not just different brands. Since they rely not on cables, electronic front derailleurs avoid this problem.
Additionally developed for specific drivetrain speeds are front derailleurs. Because the chain width and cassette spacing vary, you cannot use an 11-speed front derailleur with a 10-speed drivetrain. The guiding plates must keep the right distance to enable seamless shifting.
The biggest chainring size a front derailleur can manage is another factor to take into account. Additionally limited is the variation in size between the two chainrings. Usually, manufacturers offer sensible recommendations for these figures. Following their advice is a terrific notion if you wish for the best performance.
Mixed Compatibility
For best compatibility, it is usually advised to use the same brand and series for the front and rear derailleurs. On 9-speed or lesser systems, however, it usually works great if you want to mix and match for any reason.
Brands started adopting varying cable pull ratios to increase shifting speed and lower the effort required as 10-speed, 11-speed, and 12-speed drivetrains gained popularity. For more recent drivetrain models, keep to the same brand and series. If you wish to explore, there is naturally some flexibility, but, should problems arise, you will have to troubleshoot them on your own.
When Should I Replace or Maintain My Front Derailleur?
Regarding routine maintenance, the front derailleur is sometimes disregarded.
Like any other component of your bike, the front derailleur should be kept nice and degreased sometimes. Regularly adding a few drops of oil to the pivots will help them to stay free from sticking and run as intended.
As with your rear derailleur and brake cables, ensure the front derailleur cable housing is in good shape and replace it on occasion. Dirt and grime build up and influence shifting performance. Check also whether the derailleur's guide plates are straight. While a big curve could result in poor shifting or even damage to your bike, a small bend might produce noisy, erratic movements.
Check the derailleur arms for play as well. They can eventually loosen at the pivot points. Should excessive play exist, the derailleur may rub against the chain and fail to shift correctly. Finally, since the front derailleur interacts closely with your chainrings, it's a good idea to monitor their condition to make sure everything stays in top shape.
What Types of Front Derailleurs Are There?
Road and Gravel Bike Front Derailleurs
With much fewer possibilities than mountain bikes, front derailleurs for road and gravel bikes are still somewhat basic. However, this is not much of a problem now since 1x drivetrains have evolved as the standard for mountain bikes.
Nearly all cable routing on road and dirt bikes is bottom-pull, in which case the cable travels under the bottom bracket and pulls the front derailleur from below.
Mountain Bike Front Derailleurs
Mountain bikes need more mounting options, as front suspension exists, while road cycle front derailleurs are simple and restricted in variety.
That said, the uncertainty about selecting a front derailleur is essentially a thing of the past since 1x drivetrains now rule mountain riding.
In its most recent mountain bike models, SRAM has totally abandoned front derailleurs; Shimano is the only brand still carrying them. Front derailleur choices abound with Shimano's latest XTR M9100 and XT M8100 12-speed groupsets.
Shimano Side-Swing Front Derailleur
The side-swing design of Shimano's front derailleur lets the cable pull the derailleur arm laterally rather than up or down. First shown on the 11-speed XTR M9000 and XT M8000 groupsets, this design Developed to fit a front derailleur, the side-swing design solved the sacrifices frame builders sometimes had to make with chainline length, chainline, and tire clearance to meet expanding wheel and tire sizes.
The side-swing derailleur has a special cable routing method that draws the cable in from the front. Although this arrangement may call for zip ties to hold the cable on more modern bikes, let's be honest—it's not the most attractive or neat approach.
To suit varying frame designs, Shimano provides side-swing derailleurs with direct-mount, E-mount, and clamp-on choices.
Classic Mountain Bike Designs
Older mountain bikes with front derailleurs can have more complicated installation procedures because of variances in suspension systems. Some e-bikes and entry-level models still incorporate these more antiquated designs today.
Let's quickly review the several designs, even if these configurations are already essentially extinct.
Low Clamp (Also Known as Top Swing)
This type of front derailleur is mounted lower on the clamp, with the clamp positioned near the bottom bracket and the derailleur body sitting higher up, which is why it’s also called a "top-swing" front derailleur.
Be sure to check your seat tube diameter. Typically, this design supports 34.9mm tubes and includes shims to fit smaller diameters like 31.8mm and 28.6mm.
High Clamp (Also Known as Bottom Swing)
Popular for full-suspension systems and designs with limited room around the bottom bracket, high-clamp front derailleurs sit much higher on the frame than low-clamp ones. This type is sometimes referred to as a "bottom swing" derailleur since the clamp is above the derailleur pivot.
The approach of installation is somewhat comparable to the top-swing technique. Usually measuring 34.9mm, the normal clamp diameter can be adjusted using shims for smaller measurements.
Top-swing and bottom-swing derailleurs are commonly interchangeable on bicycles when the seat tube diameter runs consistently top to bottom. Generally speaking, top-swing derailleurs provide more room for water bottle cages, a better appearance, and, if they suit your bike, they often are somewhat lighter.
Direct Mount
Just before 1x drivetrains really took off, direct-mount front derailleurs became a popular choice. They use a single fixing bolt and have a groove on the back to align properly with the frame mount.
To install these derailleurs, the bike frame must have a compatible mounting bracket. SRAM refers to this as "High Direct Mount," while Shimano simply calls it "Direct Mount."
E-Type (Also Known as Low Direct Mount, E2, S3)
Shimano's E-Type front derailleurs typically included a backplate mounted to the bottom bracket. This design predates the direct-mount style and served as a transitional option when brands started moving away from traditional clamp designs.
Modern versions of the "E-Type" no longer feature the backplate and are sometimes referred to as "Low Direct Mount" or "E2-Type" front derailleurs.
SRAM also offers front derailleurs compatible with this mounting style, calling it "S3" or "Spec3." This method became popular because it’s easier to hide when using a 1x drivetrain.
Direct Mount S2
In addition to the common E-Type/S3 Low Direct Mount, SRAM provides two other visually similar but incompatible options.
SRAM S2 (or Spec2) is probably the most easily confused with S3 (or E-Type). It has the same 22.1mm bolt spacing but is positioned further out and lacks the 5mm offset. S2 derailleurs are relatively uncommon.
Direct Mount S1
Lastly, SRAM also offers the Low Direct Mount "S1" (Spec1) derailleur. It features a bolt spacing of 42.7mm, making it distinctively wider. This design is quite niche, and as far as we know, it was only used by Specialized in the past.
Recommended Reading:
- Beginner's Guide: Everything You Need to Know About Cassettes
- A Comprehensive Guide to Rear Derailleurs
- Super Boost Plus 157 Rear Axle Standard: Is It Here to Stay?
- Beginner's Guide: How to Find the Optimal Tire Pressure for a Road Bike
- Is the Single Chainring Drivetrain the New Trend for Road Bikes?