component-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

di2-dealer-manual-ultegra-6870

Ultegra 6870 Dealer Manual

manual-di2-rear-derailleur

Di2 Rear Derailleur User Manual

The 6870 Di2 groupset was released in 2013 and is “pro-proven” as it is a direct trickle down from Shimano’s DURA-ACE group. It stands for state-of-the-art technology, proven in pro races, the technology used in ULTEGRA 6800 series with 11-speed, advanced designed brakes, latest chain treatment and more.

Ultegra

Short Cage Rear Derailleur

<NewContentAlert title="12-speed Di2? Go here" text="If you're trying to set up your 12-speed Di2 rear derailleur, use my updated guide." link="/installation-guide/adjust-12-speed-di2-rear-derailleur-shifting-and-limits/" link_text="12-speed Di2 rear derailleur guide" />

Is your rear derailleur not shifting as smoothly as it should? Or maybe you’ve recently learned how to micro-adjust your front derailleur and want to know how to do the same with your road bike rear derailleur? Read on and I'll explain how to make small but effective adjustments to your rear derailleur.

If the term *micro-adjust* seems a bit strange to you, it is essentially the same as *indexing* a derailleur - something you might have done before with mechanical groupsets.

### Limit screws first?
You may be used to setting up your limit screws before doing any micro-adjustment, but the Shimano manual states that for Di2, it is the other way around. First, do micro-adjustment fine-tuning, and then set up your limit screws. 

Don't worry if you have already set up the limit screws, just know that if you are setting up a derailleur from scratch, you don't necessarily need to set the limits first.

Tip: If your bike has been set up properly you can skip setting the pulley distance and limits, and follow only the steps mentioned under **Adjustment Mode**.

## Check guide pulley distance
According to the [Shimano documentation](/learn-how-to-use-the-shimano-documentation/) the first step is adjusting the guide pulley distance. 

![RD adjustment from behind](https://assets.bettershifting.com/adjust_road_rd_pulley_adjustment_bf2c752ce2.png)

- Shift to the largest sprocket of the cassette
- Turn the end adjust bolt to move the guide pulley as close to the sprocket as possible but not so close that the chain gets jammed
- Shift to the smallest sprocket and check the chain doesn’t get jammed on that end of the cassette either
- If there’s any slack in the chain when the chain is mounted on the smallest chainring and smallest sprocket, adjust the end adjust bolt to eliminate this slack

## Adjustment mode
In order to make adjustments to your rear derailleur, you’ll have to enter adjustment mode. When you’re in this mode the shift buttons will only make adjustments – they won’t let you change gears. This is how it’s done:

![RD adjust fifth sprocket](https://assets.bettershifting.com/adjust_road_rd_rear_5th_sprocket_5ebd0a1a4a.png)

- Shift the front derailleur to the small chainring.
- Shift the rear derailleur to the 5th largest sprocket.
- Press and hold the button on your junction box until the red LED illuminates, indicating you’re in adjustment mode.

Easy, right? Now you can micro-adjust your rear derailleur using the buttons on the shift lever:

![RD button direction](https://assets.bettershifting.com/adjust_road_rd_buttons_58967c43ed.png)

- Press shifting button **X** to move the rear derailleur **one step** towards the inside (larger sprocket)
- While turning the crank/front chainring keep moving the rear derailleur towards the **4th largest** sprocket until it makes a slight noise
- The chain now touches the **4th** sprocket. Press the **Y** button four times to move the rear derailleur **4 steps back** (towards the 11T).
- Press the junction box button until the red LED turns off. You have now left adjustment mode.
- Now is the time to make any adjustments to your high/low limit screws – if you need to.

## Set the high/low end stopper bolts
These bolts limit the range of the rear derailleur, meaning it won’t shift to positions that don’t contain a sprocket. Note that Di2 stopper bolts are different from normal stopper bolts. The Di2 derailleurs slightly ‘overshift’ and then move the derailleur cage back in a. This is intentional, but requires you to set up the adjustment bolts a bit less restrictive than you’d do with a mechanical setup.

If your adjustment bolts are over-tightened you might experience:

- Gears do not shift to the top/low gear or shift back by one gear after about 5 seconds
- Noise that doesn’t stop
- The battery level drops quickly due to extra load being placed on the motor
- The motor may be damaged. (irreparable)

## Low stopper bolt

![RD low stopper bolt](https://assets.bettershifting.com/adjust_road_rd_low_stopper_bolt_252a340c8e.png)

Shift the rear derailleur to the **largest** sprocket (easiest gear) and then tighten the low stopper bolt until it just touches the left link (of the rear derailleur). 

If this seems a bit cryptic: it’ll become clear once you’re doing it – don’t worry. The image below shows what to look for when adjusting the Low stopper bolt. You should be able to figure out the High bolt from this.

![RD low limit stopper bolt](https://assets.bettershifting.com/adjust_road_rd_low_limit_stopper_bolt_b96bc9cf6b.png)

Then shift the rear derailleur down three gears and then back to the largest sprocket again. It should shift to the easiest gear just fine.

If it doesn't and you hear a clicking or ticking sound, or if it shifts back within five seconds, relax the limit screw a bit. Don't unscrew it too much though - you don't want the chain to fall off between cassette and spokes.

## Top/high stopper bolt

![RD high stopper bolt](https://assets.bettershifting.com/adjust_road_rd_high_stopper_bolt_4ea0adcef3.png)

Next set up your high stopper bolt. Shift to the **smallest sprocket** and then tighten the adjustment bolt until it touches the left link at the position where the rear derailleur stops.

Then, turn the bolt counter-clockwise to loosen it **one full turn** to allow the rear derailleur to ‘*over-shift*’. (when it shifts, the derailleur will move slightly past its final position and then move back)

This video describes the process rather well:

<YouTube videoId="HIvsY4AtQpI" />

## All done!
Your rear derailleur should be set up perfectly now. Of course, you can always enter adjustment mode again and make small changes but this should be your baseline setup.

Note that while you could do the entire process on the bike, it’s probably best to do it with the bike on a bike repair stand. This will allow you to notice when the chain is touching the 4th sprocket more easily.

The amount of steps you can make differs per hardware series (33 total for 6870, 25 for 9070). If you want to know the number of steps available please have a look at your series’ dealer manual. Alternatively, [connect your bike to your Windows computer](/how-to-connect-your-di2-system-to-your-windows-computer/) and use the e-Tube project software to look up the current setting and available steps.

You can also adjust your [XTR Di2 and XT Di2 mountain bike rear derailleurs](/how-to-adjust-your-mountain-bike-di2-rear-derailleur). Read more on that [right here](/how-to-adjust-your-mountain-bike-di2-rear-derailleur).

featured-gear-position-control

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.

Micro-adjust your 10-speed and 11-speed road bike Di2 rear derailleur

The installation method for the [RD-R8050](/component/ultegra-short-cage-shadow-rear-derailleur-rd-r8050-ss/) / [RD-R9150](/component/dura-ace-short-cage-shadow-rear-derailleur-rd-r9150-ss/) / [RD-6870](/component/ultegra-short-cage-rear-derailleur-rd-6870-ss/) and [RD-9070](/component/dura-ace-short-cage-rear-derailleur-rd-9070-ss/) rear derailleurs is similar to that of traditional road rear derailleurs, but setting the limits and indexing is slightly different. You first index the rear derailleur and only then set the top and low limits.  

If your rear derailleur has a clutch mechanism then you're probably looking for this installation guide: [RD-RX805 / RX-RX815 / RX-RX817 installation guide](/rd-rx805-rd-rx815-rd-rx817-di2-rear-derailleur-installation-guide/).

## Mount the derailleur to the frame
The RD-R8050 and RD-R9150 derailleurs are direct mount ready and come with a ***B2-link plate***. Whether or not you need to use this depends on the rear derailleur mount on your frame. Generally, direct mounts are in line with the seat stay, while a standard mount will make a sharper bend down. The image below should help you identify the mount on your frame:

![direct mount vs standard mount](https://assets.bettershifting.com/rd_rx_installation_guide_rear_derailleur_direct_vs_standard_mount_ea968de92d.png)

## Standard mount - RD-R8050 / RD-R9150
On a standard mount frame you install the derailleur with the ***B2-link plate*** attached. It should come this way out of the box. If the ***B2-link plate*** is not installed, do so now – it is colored green in the image above.

Apply a small amount of grease to the mounting bolt and secure the rear derailleur to the frame. Before tightening it fully, make sure the stopper plate touches the B-tension stop, with no gap between them. 

**IMPORTANT**. You may be tempted to install the derailleur hanger B-tension stop between the stopper plate and the *other* plate. Don't. **Make sure the B-tension stop touches the stopper plate** with no gap in-between, as shown in the image below.  I've coloured them yellow and blue respectively.

![RD-R8050 / RD-R9150 / RD-6870 / RD-9070 stopper plate](https://assets.bettershifting.com/install_rd_r8050_r9150_9070_6870_3c4bb29b86.png)

### RD-6870 / RD-9070 Rear derailleurs
Easy! Simply screw the derailleur attachment screw into the mount. The recommended torque is 8-10Nm.  The end result should look similar to the image above - except there is only one tab on the derailleur - the stopper tab (coloured blue).

## Direct mount - RD-R8050 / RD-R9150
Is your frame equipped with a direct rear derailleur mount? Then remove the ***B2-link*** from the rear derailleur so that you can mount it directly onto the frame. You do this by removing the bracket axle using a **size 5 hex wrench**. Remove the link and attach the derailleur to the frame using the bracket axle.

![RD-R8050 / RD-R9150 B2-link](https://assets.bettershifting.com/install_rd_r8050_r9150_9070_6870_b2_link_05f3eb9a85.png)

## Connect the electric wire
If you haven’t run the [EW-SD50 electric wire](/component/di2-electric-wire-ew-sd50/) to the rear derailleur yet, do so now. Now use the Di2 plug tool to push the electric wire into the connector. Push firmly until you feel (and possibly hear) it click into the socket.

## Set the end adjustment screw
Now first make sure the rest of the system is installed and that you can shift both derailleurs. The next step is to set the end adjustment screw (or ***b-screw***). This will set the angle of the rear derailleur and change the distance between the guide pulley and chain on the cassette.

Shift the front derailleur to the smallest chainring and the rear derailleur to the largest sprocket. Use a **size 2 hex wrench** to turn the adjustment screw and move the guide pulley as close to the sprocket as possible but not so close that the chain gets jammed.

![RD set the b-screw](https://assets.bettershifting.com/rd_rx_installation_guide_rear_derailleur_b_screw_fe8007ba6b.png)

Shimano hasn't published any information on the recommended distance between the guide pulley and the sprockets for 11-speed Di2, but this is what they say in the 12-speed documentation:

- **11-28T** cassette: 18mm
- **11-30T** cassette: 14mm
- **11-32T** cassette: 10mm
- **11-34T** cassette: 6mm

Now shift to the smallest sprocket and make sure the chain does not get jammed. If there is any slack in the chain in this gear use the adjustment bolt to eliminate this slack.

## Micro-adjust the rear derailleur
Before setting the high/low limit screws you will have to micro-adjust or index the rear derailleur. Note that this is different from how you would set up mechanical rear derailleur – there you would set the limit screws first and then do indexing.

![RD adjustment 5th sprocket](https://assets.bettershifting.com/rd_rx_installation_guide_cassette_fifth_sprocket_5f128c1c9c.png)

- Shift the front derailleur to the small chainring.
- Shift the rear derailleur to the fifth sprocket.
- Press and hold the button on your junction box until the red LED illuminates, indicating you’re in adjustment mode.

You can now adjust the position of the rear derailleur using the shift buttons:

![RD adjustment switch X](https://assets.bettershifting.com/rd_rx_installation_guide_rear_derailleur_adjustment_x_7dfaf6a18e.png)

- Press the [**X**] button while also turning the crank to move the guide pulley towards the 4th sprocket.
- Keep doing this until the chain makes contact with the 4th gear and a subtle noise is heard.
- Note that while you are in adjustment mode the guide pulley will overrun slightly and then move back a bit. When checking the position of the guide pulley and gear, make sure the derailleur has come to a stop.

![RD Adjustment Y switch](https://assets.bettershifting.com/rd_rx_installation_guide_rear_derailleur_adjustment_y_7c8b459555.png)

Now press the [**Y**] switch five times in order to move the guide pulley five steps back towards the smallest sprockets. The rear derailleur should be indexed now. This will be the starting point for all future adjustments.

To leave adjustment mode just press and hold the button on the junction box until the LED turns off and you will leave adjustment mode.

Use both the front and rear derailleur to shift through all the gears, making sure no chain rub occurs in any of them. If it does, go back to adjustment mode to tweak the rear derailleur indexing.

## Set the low/high stopper bolts
Adjusting the low/high stopper bolts is a relatively easy affair. Let’s first set the low stopper bolt.

- Shift the rear derailleur to the **largest sprocket** (easiest gear).
- Now use a **size 2 hex wrench** to tighten the low side stopper bolt until it just touches the low side stopper. This is the bolt with an **L** next to it.

Confused? This image should clarify things a bit: If not, just leave a comment or [send me a message](/contact/)

![RD low limit stopper bolt](https://assets.bettershifting.com/adjust_road_rd_low_limit_stopper_bolt_b96bc9cf6b.png)

To check whether your limit setting is correct, shift the rear derailleur down three gears and then back to the largest sprocket again. It should shift to the easiest gear just fine.

### High stopper / top limit
Now we’ll set the high or top side stopper bolt.

- Shift the rear derailleur to the **smallest sprocket** or hardest gear.
- Tighten the top stopper bolt with a **size 2 hex wrench** until it just touches the top-side stopper. This is the bolt with an **H** next to it.
- Turn the top-side stopper bolt counterclockwise one turn to loosen it and allow for the rear derailleur to overshift.

![RD stopper bolt](https://assets.bettershifting.com/rd_rx_installation_guide_low_top_side_stopper_bolt_rear_derailleur_cca353bee7.png)

Note that if you overtighten either stopper bolt the derailleur will not stay in that highest or lowest gear and shift back within five seconds. When this is the case you'll also hear some clicking or ticking, indicating that the derailleur is blocked from fully completing the shift.

Also, according to Shimano, one of the following could happen:

- Chain noise does not stop.
- The battery level drops quickly because extra load is being placed on the motor.
- The motor may be damaged due to overload (irreparable).

Need some extra guidance? I think this video describes the process rather well:

<YouTube videoId="HIvsY4AtQpI" />

## All done!
Your rear derailleur should now be installed and set up pretty well. If you're having problems however, just leave a comment or [send me a message](/contact/) and I'll do my best to help you!


featured-adjust-road-rd

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.

Shimano model number:	RD-6870-SS
Weight:	257 g
E-Tube ports:	1
E-Tube Port type:	SD50
Type:	Rear Derailleur
Component series:	Ultegra 6870 (Road)
Downloads:	Ultegra 6870 Dealer Manual Di2 Rear Derailleur User Manual

Short Cage Rear Derailleur

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