The rear derailleur is the star of the Gran Compe groupset. With machined aluminium jockey wheels spinning on sealed bearings and a carbon outer linkage plate, it looks good and works refreshingly well.
Performance with both nine-speed and 10-speed Shimano levers as well as the Gran Compe units was commendable; it even handled the abuse of chasing a chain up and down an 11-32 block during a muddy cyclo-cross race.
At 198g for our test unit, the weight of the rear mech puts it almost exactly halfway between SRAM Rival and Ultegra offerings, but it’s nearly twice the price of both.
Overall, the Gran Compe Zero rear mech would make a good upgrade for lower-end 10-speed and any nine-speed users looking for something different and willing to pay a premium.