Rear Derailleurs

❓1. How do I check the compatibility of the derailleur with my transmission?

• Number of speeds : the derailleur must match exactly (10, 11, 12 speed).
  
• Order type :
  SRAM ↔ works with SRAM controller.
  Shimano ↔ works with Shimano controller.
  Both systems are generally not compatible (different print).
  
  
• Derailleur Capacity : must cover the size of largest sprocket (ex: 50/51/52 teeth in 12 speeds).
  
• Screed :
  Short (SS) → Cassette at a small beach (Road, urban).
  Average (GS) → MTB XC / Trail.
  Long (SGS) → large cassettes (e.g.: 10–51).
  
  
• Fixing : classic paw vs typical screed UDH (SRAM Transmission AXS).

❓2. How do I choose according to my practice (XC, trail, enduro, DH)?

• XC/Marathon : Light weight, medium tread, precise and fast operation. Efficiency-oriented models (e.g. Shimano XT / SRAM GX).
  
• Trail / All-Mountain : Robustness + wide speed range.
  Derailleurs with high-performance clutch (anti-shock/anti-chain).
  
• Enduro : Reinforced derailleur, rigid cage, anti-breakage protection. Powerful clutch to avoid noise and derailments.
  
• DH : Derailleur short cope, ultra resistant, Cassette very specific. Priority to chain retention more than speed range.

❓3. Which technologies and options to favor?

• Clutch : essential in MTB → reduces chain skipping and noise.
  
• Mechanical vs. electrical choice (AXS) :
  Mechanics → reliable, economical, easy to maintain.
  Electric (SRAM AXS) → exceptional precision, self-adjusting, cable-free, but more expensive.
  
• Contoured Top Caster : improves precision in large gears.
  
• Direct Mount (UDH Transmission) : Stiffer, more precise, designed for compatible modern frames.
  Very resistant to impacts.

❓4. What materials and what level of range to choose?

• Aluminum : excellent weight/strength compromise.
  
• Steel : very robust, ideal for small budget or intensive use.
  
• Carbon / composite : light, often high-end, good rigidity.
  
• Bearings :
  Simple rings → economic.
  Sealed bearings → better durability and fluidity.
  
• Moving upmarket = + precision, + rigidity, + silence, + durability.

If you want to know more, discover our advice guide:

How to choose your rear derailleur MTB

How to properly adjust your rear derailleur MTB