Specifications Shimano RD 1055

a downhill mountainbike gear wheel and gearshift mechanism image by Stephen Gibson from Fotolia.com

The Japanese company Shimano manufactures clothing and components for bicycles. One of their midrange road bike groupsets is the 105 series. A groupset comprises the majority of hardware on a bike, including gears, levers, brake calipers, cranks and derailleurs.

The rear derailleur moves the chain over the rear gears when you shift into a harder or easier gear using the right hand shifter. The RD 1055 is an older rear derailleur in the Shimano 105 groupset.

Appearance and Weight

The RD 1055 is available in silver with a brushed finish. The jockey wheels are black and the derailleur is labelled with "Shimano 105" on the front. The RD 1055 weighs 246 grams.

Material and Bolt Size

This rear derailleur is made of an aluminium alloy. It attaches to the frame with a 5-mm bolt.

Compatible Shifting Systems

The RD 1055 works with Shimano's Index Shifting (SIS), System Total Integration (STI) and Friction shifting systems. Index shifting refers to shifting mechanisms that click into each gear, as opposed to older systems where you continued to move the shifter until the gear changed (this is friction shifting). STI refers to bikes with an integrated shifter and brake lever. Older models had shifters in various places on the bike frame.


The RD 1055 has a capacity of 28. This is the amount of slack within the chain your derailleur can take up. It is the sum of your front chainring range plus your rear gear range. For example if you have two front chainrings with 52 teeth and 42 teeth, the range is 10. If your largest rear gear has 28 teeth and the smallest has 10 teeth, the rear range is 18. Adding these two ranges together gives a capacity of 28.


The RD 1055 was manufactured in the 1990s. It is no longer available for purchase from Shimano and must be bought used.