Understanding Di2 derailleur specifications
Shimano front derailleur and rear derailleur specifications... what do they mean, really? This page explains all of them, and why they matter.
Short Cage Rear Derailleur
Ultegra RD-6870-SS
The Shimano RD-6870-SS is their short cage rear derailleur for the 6870 series.
It supports a max front difference of 16T, a low sprocket minimum of 23T, and a low sprocket maximum of 28T. The top sprocket maximum is 14T and the minimum is 11T. It has a total capacity of 33T.
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It also features Shimano's Crash Protection Mode - this prevents shifting after a crash to make sure the rear derailleur is damaged any further. To restore shifting functionality have a look at the FAQ: I had a small crash and my rear derailleur stopped working.
When paired with 6870 or newer components and the BT-DN110 battery, this derailleur supports synchronized shift.
Specifications
- Model code: RD-6870-SS
- Series: Ultegra (6870)
- Weight: 257g
- Speeds: 11
- SD50 ports: 1
- Max front difference: 16T
- Total capacity: 33T
- Low sprocket max: 28T
- Low sprocket min: 23T
- Top sprocket min: 11T
- Top sprocket max: 14T
- Pulley teeth: 11
- Mount: Conventional mount
- RD type: Non-shadow RD
- Clutch: No
Related components
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Micro-adjust your 10-speed and 11-speed road bike Di2 rear derailleur
Indexing, trimming, or fine-tuning Di2 rear derailleurs is done through micro-adjustment. Read how to set up your Di2 rear derailleur perfectly and ride without those grinding noises.
Installation Guide: 10-speed and 11-speed Di2 road Rear Derailleur
Bought a new Di2 rear derailleur and need some help installing it? Read how to install the RD-R8050 / RD-R9150 / RD-6870 / RD-9070 Di2 rear derailleurs.
Synchronized Shifting - the complete guide
Synchronized Shifting - what is it exactly? What does it do and how can you set it up? This page will guide you through the process of setting up synchro shift.
Manuals & other documents
Firmware updates
Below is an overview of all known firmware updates for this component. The changelog texts are Shimano's, and quite often they're a bit cryptic - sorry!
3.0.1
Bug fixing
2.6.3
Bug fixing
2.6.2
Fixed SM-BTR2 bug
2.6.0
Enhancement of energy-saving.
2.5.0
Enhancement of shifting performance and anti-vibration function