Derailleurs

A rear derailleur moves the chain across the cassette at the back of the bike and handles the majority of your gear changes. A front derailleur shifts the chain between chainrings at the crank and is only found on bikes with multiple chainrings. Most modern mountain bikes have moved to single chainring setups, meaning a front derailleur may not be required, while road bikes more commonly still use both.

Compatibility depends on several factors including the number of speeds your drivetrain runs, the brand of your groupset, and whether you have a road or MTB setup. Derailleurs are designed to work within specific systems, so a derailleur built for an 11-speed road groupset will not work correctly with a 12-speed MTB drivetrain. Checking your existing groupset brand and speed count before purchasing is the most reliable way to ensure a correct match.

If your derailleur is bent, cracked, or has damaged pivot points, adjustment alone will not restore reliable shifting and replacement is the better option. Worn jockey wheels can also cause poor shifting and are worth checking before replacing the full derailleur, as they are a more affordable fix. If the hanger is bent but the derailleur itself is undamaged, replacing the derailleur hanger is often all that is needed.

When upgrading, consider moving to a higher tier within your existing groupset family to ensure compatibility while gaining improved shifting precision and reduced weight. Higher-end derailleurs typically offer better build quality, smoother actuation, and more consistent performance under load or in rough conditions. It is important to stay within the same speed range and brand ecosystem unless you are planning a full drivetrain overhaul.

MTB and road derailleurs are not interchangeable as they are designed around different cable pull ratios, cassette sizes, and riding demands. MTB derailleurs are built to handle wider gear ranges and greater chain slack, while road derailleurs are optimised for closer gear spacing and lighter conditions.