Shimano Dura Ace 7900 RD-7900 Rear Derailleur Short Cage 10 Speed

The Shimano Dura-Ace FD-7900 front derailleur is a 10-speed road component known for eliminating the manual "trim" function, allowing riders to use the full range of rear gears without chain rub. It was designed specifically for use with the Dura-Ace ST-7900 shifters because of its unique cable pull ratio. 

Key Specifications:

According to manufacturers and technical experts, the FD-7900 features:

• Weight: Extremely light at approximately 64g to 67g for the braze-on version.

• Capacity: A maximum front tooth difference of 16 teeth, supporting outer chainrings from 50T to 56T.

• Construction: Cold-forged aluminium body with nickel-plated alloy cage plates for high rigidity and durability.

• Design: Features an extra-wide pivot link to reduce flex and improve shifting precision under load. 

Compatibility Requirements:

Derailleur has strict compatibility requirements:

• Shifters: It is not backwards compatible with older Dura-Ace 7800 series or other 10-speed Shimano shifters because of its revised cable pull ratio. It must be paired with Dura-Ace ST-7900 STI levers.

• Chain: Optimized for the asymmetric Shimano 10-speed directional chains (e.g., CN-7900) to ensure the rub-free performance.