Its clear SRAM has been very busy improving their flagship Red rear derailleur with significant enchantments making it smoother and quieter than ever before.
SRAM achieves silent shifting thanks mainly to refining the tooth geometry of the new AeroGlide jockey wheels. A new pulley cage works to more precisely manage the chain. Even though the pulleys are newly designed, they retain the ultra-smooth, Blackbox ceramic bearings to reduce drivetrain friction to a minimum.
Other improvements include more clearance with a 28t cassette due to the addition of a longer B knuckle. A new spring-fixed barrel adjuster gives a lighter action while fine-tuning. The Red rear derailleur was already lighter than seems possible at 146 grams but SRAM just had to add a hollow titanium pinch bolt.
The new Red Aero Glide rear derailleur retains SRAM's Exact Actuation for easy set up and precise shifts. Exact actuation means the derailleur moves the same distance for every shift and the distance the cable travels with every click is identical. So even and exact shifts occur over whole shifting range. The Red rear derailleur is able to handle rear cassettes up to 28 teeth and both standard and compact cranks.