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The RD-R8150 rear derailleur is part of Shimano's new **12 speed** system, allowing for both wired and wireless communication between the derailleur and shift l

r8150-r9250-rear-derailleur-manual.pdf

RD-R9250 / RD-R8150 User Manual

When Shimano announced the 12-speed DURA-ACE R9200 groupset, they also announced Ultegra R8100. Just like its DURA-ACE cousin, this groupset is all about 12-speed, wireless shifting. Also, for the very first time, Shimano have produced an Ultegra Power Meter.

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Ultegra

Shadow Rear Derailleur (12 speed)

If you’ve been riding Di2 bikes for a while, you may have read my [earlier guide on setting up 10-speed and 11-speed rear derailleurs](https://bettershifting.com/micro-adjust-your-road-bike-di2-rear-derailleur/).

It involves pressing the main junction box button to enter adjustment mode, and then using the shift buttons to adjust the rear derailleur.

The process is very similar for 12-speed Di2 rear derailleurs, but here’s the thing: there is no main junction box.

Well, sort of. All of this functionality (including the LED), has moved to the rear derailleur. This impacts the guide enough to warrant a completely new page, and here we are.

I'll explain how to set the [RD-R9250](/component/dura-ace-shadow-rear-derailleur-rd-r9250/) and [RD-R8150](/component/ultegra-shadow-rear-derailleur-rd-r8150/) B-screw, limits, and how to fine-tune the shifting (micro-adjust).

## The steps involved
Setting up a 12-speed rear derailleur is done through four steps. They are:

- [Adjust the B-screw](#adjustbscrew)
- [Micro-adjust the gear shifting](#microadjust)
- [Set the low limit](#setlowlimit)
- [Set the high limit](#sethighlimit)

Alternatively, since the rear derailleur has BluetoothLE/ANT functionality built into it, you can now also set up the rear derailleur using the mobile app - [E-Tube Cyclist](https://bettershifting.com/di2-e-tube-software-and-downloads/).

## Adjust the B-screw {#adjustbscrew}
Just like before, the first step is to set up the B-screw. Tightening or loosening the B-screw changes the distance between the cassette sprockets (or cogs) and the guide pulley.

To get started, first shift the **front derailleur** to the **smallest chainring**. Shift the **rear derailleur** to the **largest sprocket**, or easiest gear.

Shimano’s dealer manual states that you should be turning the crank arm **in reverse** as you do this. The training videos don’t mention this at all, so it *probably* doesn’t matter all that much.

![Turn the B-screw to move the guide pulley](https://assets.bettershifting.com/adjust_rd_b_screw_direction_bc288b5922.jpg)

Next, we’ll turn the B-screw to adjust the gap between the **guide pulley** and the **largest** sprocket. The recommended gap depends on the cassette used.

This is Shimano’s guideline:

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

Alternatively, you can use the **GG adjustment gauge**. This should be included with the rear derailleur. If it isn’t, and you’d like to buy one, the part number is **Y3GK89600**.

If you have access to a 3D-printer, you can try printing one. Chris Heerschap published a model of the tool on [ThingiVerse](https://www.thingiverse.com/thing:5186418).

![Micro-adjust your 12-speed rear derailleur](https://assets.bettershifting.com/adjust_rd_gg_gauge_ab14a25b64.jpg)


You set the **adjustment gauge** on the plate as shown above, and then turn the B-screw to align the tip of the cogs with the correct line. 

If you’re using a **30T** cassette, use the top line. If you’re using a **34T** cassette, use the lower line. For **28T** cassettes you’d use the top of the adjustment gauge.

## Micro-adjust the gear shifting {#microadjust}
Next you’ll have to fine-tune the gearing, using micro-adjustment. 

First, shift the rear derailleur to the 5th gear from the largest sprocket. This will ensure the chain line is as straight as possible.

![Adjust your RD starting in the 5th gear](https://assets.bettershifting.com/adjust_rd_5thgear_7434706008.png)

Press and hold the rear derailleur button for about **2 - 5 seconds** to enter **adjustment mode**. When in this mode, the LED lights up **yellow**.

Once the system is in adjustment mode, press the button highlighted below, while turning the cranks. This will move the rear derailleur toward the larger sprockets, in tiny steps.

![Adjust the RD towards gear 4, until it rubs](https://assets.bettershifting.com/adjust_rd_until_rub_4th_gear_2da076a13e.png)

Keep doing this until the chain touches the **4th sprocket**, and a slight rubbing noise can be heard. 

At this point, you’ll have to back off the rear derailleur a bit to move it to its final position. Press the button shown below four times.

![Move the RD back 4 steps, towards gear 5](https://assets.bettershifting.com/adjust_rd_move_back_f15014b3fa.png)

Press and hold the rear derailleur button for about **0.5 seconds**, and you’ll exit adjustment mode.

The derailleur should now be set correctly. This is just a starting point though, so shift through all the gears and double-check that they all work well. Make further adjustments if necessary.

Note that at this point you haven’t set the derailleur limits yet, so be careful not to shift the chain off either end of the cassette. Also, if the derailleur doesn’t shift onto the last gears, that is OK at this point. As long as all the other gears are shifting fine, don’t worry.

If you find that your derailleur shifts well in the middle of the cassette, but performance degrades at either end, consider checking your derailleur hanger alignment. 

Dave Rome wrote a really good guide on derailleur hanger tools right here: [derailleur hanger alignment tools on CyclingTips.com](https://cyclingtips.com/2021/12/the-best-derailleur-hanger-alignment-tool-9-tested/).

## Set the low limit {#setlowlimit}
With the derailleur shifting set up, let’s now set the low limit.
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.

It’ll look similar to this:

![The derailleur's low limit stopper bolt](https://assets.bettershifting.com/adjust_road_rd_low_limit_stopper_bolt_b96bc9cf6b.png)

If you’re confused and can’t get it right, just [send me a message](/contact/) and I’ll do my best to help.

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.

If it doesn’t, relax the limit screw a bit, and try again.
## Set the high limit {#sethighlimit}
Now we’ll set the high 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**.

![Set the stopper bolts](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.

If this happens to you, loosen the top side stopper bolt a bit, and check the shifting again.

Shimano says that the following could happen, if your limits are set too tight:

- 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).

## All done!
Your rear derailleur should now be installed and set up pretty well. If you're having problems, or just cannot get it right - just leave a comment or [send me a message](/contact/) and I'll do my best to help you!







Micro-adjust your 12-speed rear derailleur

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This page shows you how to set up your 12-speed rear derailleur B-screw, limits, and fine-tune the shifting using micro-adjust. The process is similar to that of the 10-speed and 12-speed rear derailleurs.

Shimano model number:	RD-R8150
Weight:	262 g
E-Tube ports:	1
E-Tube Port type:	SD300
Type:	Rear Derailleur
Component series:	Ultegra R8100 (Road)
Downloads:	RD-R9250 / RD-R8150 User Manual

Shadow Rear Derailleur (12 speed)

Details & Specifications

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