MTB front derailleurs

How to choose a mountain bike front derailleur

Double and triple chainring setups are still found on many touring and entry-level mountain bikes, as well as older bikes. Shimano supplies most replacement options.

Which mounting type?

• Clamp : clamps onto the seat tube. Check the diameter (28.6 / 31.8 / 34.9 mm).
• Direct Mount : bolts onto tabs welded to the frame, without a clamp.
• Type E : mounts at the bottom bracket, sandwiched in place.
• The frame determines the mounting type: check what is fitted before ordering.

Top clamp or bottom clamp?

• Top clamp (Top Swing) : the derailleur body sits below the clamp, for frames with limited clearance.
• Bottom clamp (Down Swing) : traditional mounting, with the clamp above.
• Side Swing : a more recent Shimano mounting system, with side pull to clear the tyre.
• These variants are not interchangeable: the cable approaches from a different side.

How many chainrings and speeds?

• A derailleur 2x and a 3x are not interchangeable: the travel and height differ.
• The number of speeds must match the left-hand shifter.
• Check the maximum number of teeth supported by the derailleur.

Should you switch to a single chainring?

A single chainring simplifies maintenance and eliminates one shifter, but requires a wide-range cassette, a narrow-wide chainring and often a new rear derailleur. On a loaded touring bike or for very steep terrain, a well-adjusted double chainring setup still has real benefits.

See also: MTB chainrings · MTB gear shifters · MTB cranksets and crank arms