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HardwareMTBXT M8050XTR M9050

How to adjust your mountain bike Di2 rear derailleur

mtb rear derailleur micro-adjust

A short while ago we wrote a post on how to micro-adjust your road di2 rear derailleur and front derailleur. This time we’ll explain how to do the same with your mountain bike rear derailleur. The process is similar, but slightly different.

Set up the rear derailleur

Make sure your rear derailleur is set up correctly – especially the distance between the guide pulley and largest sprocket:

  • On a 2x bike, shift the front derailleur to the small chainring.
  • Shift to the largest sprocket

Now check the distance between the guide pulley and the largest sprocket is within the specified range. Turn the B-screw if it isn’t – have a look at the image below for directions on how which direction and what the acceptable ranges are.

Di2 rear derailleur guide pulley distance

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:

5th rear sprocket

  • Shift the rear derailleur to the 5th largest sprocket.
  • If you use Junction A: Press and hold the button on your junction box until the red LED illuminates, indicating you’re in adjustment mode.
  • If you use System Information Display: Press (read note!) the button on the lower left part of the display once to enter adjustment mode. The adjustment indicator “R” will flash (“R” stands for Rear)
    Note: how long this ‘single press’ is varies, this can take anywhere from 0.5 to 2 seconds according to Shimano.

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

Adjust rear derailleur buttons

  • Press shifting button Y to move the rear derailleur one step towards the inside (larger sprocket)
    If you’re using the System Information Display you’ll see the current adjustment setting on the screen.
  • 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 X button five times to move the rear derailleur 5 steps to the outside.
  • Press the Junction Box/Information Display button until the red LED turns off or the blinking R stops blinking. You have now left adjustment mode.

Your rear derailleur should (almost) 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.

The only thing left to do now is to check and correct the high/low side stopper adjustment bolts. We’ll do the low stopper bolt first (largest sprocket).

Low side stopper bolt

  • Shift the rear derailleur to the largest sprocket
  • Tighten the low-side adjustment bolt until it just touches the outer link
    (if it’s tightened too much it either won’t shift, make noise or shift back by one gear after about 5 seconds)

Now let’s do the high stopper bolt:

High side stopper bolt

  • Shift to the smallest sprocket
  • Tighten the high-side adjustment bolt until it just touches the left link at the position where the rear derailleur stops.

Note that while you could do the micro-adjusting 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.