Derailleur hangers and city bike derailleurs

Derailleur or internal gear hub: what does your bike have?

Many city bikes change gear inside the rear hub, without a derailleur: the chain stays lined up on a single sprocket. Hybrids, touring bikes and a large share of e-bikes, on the other hand, use a rear derailleur. Its parallelogram, pulled by the shifter cable and returned by a spring, moves the chain along the cassette, while the cage and its two jockey wheels keep the chain under tension. On a bike with two or three chainrings, a front derailleur moves the chain from one chainring to another.

Choosing a city bike derailleur: speeds, cage and compatibility

The derailleur must be designed for the same number of speeds as the shifter and the cassette, and for the same make of shifter: the ratio between the length of cable pulled and the movement of the derailleur varies from one manufacturer and one generation to another. Then check the largest sprocket it accepts and its total capacity, that is, the difference in teeth the cage can take up between the smallest and the largest combination. A long cage suits wide-range cassettes and triple chainsets, a short cage close-ratio gearing.

Some families require their own ecosystem. Shimano Cues derailleurs work with the Linkglide cassettes and shifters from the same range, and not with another system. Models with a clutch reduce chain slap on cobbles and tracks.

A derailleur for an e-bike?

On an e-bike, the drivetrain takes both the rider's effort and the motor's, and gear changes are often made under load. Several manufacturers offer derailleurs, cassettes and chains designed for this use, such as the E-Bike version of the Box One Prime. Whatever the equipment, ease off the pressure on the pedals for a moment as you change sprocket: the chain shifts more cleanly and the drivetrain wears less quickly.

The derailleur hanger, a sacrificial part

Between the frame and the rear derailleur, the hanger acts as a fuse: designed to give way first, it bends or breaks in a crash and spares the frame. You can recognise a bent hanger by gears that skip despite correct adjustment, or by a derailleur that moves closer to the spokes at the bottom of the cassette. There are hundreds of shapes, each specific to a frame: start from the make, model and model year of your bike, then compare the shape and holes with the original hanger.

On many recent frames, the UDH universal derailleur hanger launched by Sram replaces specific models and makes roadside repairs easier. On a cycling trip, a spare hanger takes up almost no room in a pannier.

Derailleur adjustment and maintenance

Two limit screws restrict the derailleur's travel towards the top and bottom of the cassette, and the barrel adjuster where the outer casing enters sets the cable tension. A chain that hesitates to shift up or down can usually be corrected with a quarter turn of this barrel adjuster. A frayed cable, dirty outer casing or seized jockey wheels also spoil shifting: clean the jockey wheels and replace the cable and outer casing as soon as they drag.

The other parts of a city bike drivetrain

The derailleur works as a unit with the gear cables and outers that control it and the cassettes and chains it moves. To switch to a double or triple chainset, also see city bike chainsets. Performance-oriented derailleurs have their own pages: road bike derailleurs, MTB derailleurs and gravel derailleurs.

Which derailleur and hanger brands should you choose?

Marwi, a company based in Rotterdam, specialises in derailleur hangers: its GH references, in forged aluminium, are each matched to the frames they fit, from Focus to Haibike by way of Cube, and part of the range is sold under the Union name.

Box Components, founded in California by Toby Henderson, a former BMX and mountain bike racer, offers wide-range nine-speed Prime rear derailleurs, with a long or extra-long cage and in an E-Bike version.

XLC, part of the Dutch Accell group, offers its aluminium hangers under DO references, such as the DO-A100 for several Haibike e-bikes and touring bikes or the DO-A109 for Sinus models.

Shimano covers every use, from the Cues RD-U8050 derailleur for 10 or 11 speeds to the Deore XT and XTR for mountain biking, and also sells the plates and spare parts for its cages.

Derailleurs on sale and new arrivals

For end-of-line derailleurs and hangers, see our city bike drivetrain clearance; recent arrivals are in new arrivals. Take advantage of the seasonal sales or Black Friday to slip a spare hanger into your repair kit.

Frequently asked questions

How do you tell if the derailleur hanger is bent?

Look at the bike from behind, with the chain on the smallest sprocket: the derailleur should be perfectly vertical and its jockey wheels lined up under the sprocket. If it leans towards the wheel, the hanger is bent. A workshop straightens it with an alignment tool; a hanger that has already been straightened or is cracked should be replaced.

Which rear derailleur for a 7 or 8-speed bike?

Choose a derailleur rated for 7 or 8 speeds, from the same brand as the shifter, then check the largest sprocket it accepts and how it mounts: on a bolted hanger, or directly on the wheel axle on some entry-level bikes. These simple derailleurs come with a short or long cage depending on the gear range.

Can you combine a derailleur and a shifter from different brands?

As a general rule, no: each brand, and sometimes each generation, pulls a different length of cable with each click. The derailleur would sit badly under the sprockets and the gears would not line up. Keep a shifter and a derailleur from the same family.

Why does my chain skip gears?

The most common causes are cable tension that needs adjusting, a bent hanger, a stretched chain or a worn cassette. Start with the barrel adjuster, check the derailleur's alignment, then measure chain wear with a checker. Dirty outer casing can also slow the derailleur's return.

Do you need a specific derailleur on an e-bike?

It is not compulsory: the original derailleur is designed for the bike. As a replacement, a version designed for e-bikes, sturdier and often fitted with a clutch, copes better with shifting under load. The key is to keep the same number of speeds and the same family of shifters.