Micro-adjust / set your front derailleur limits
Installing a new Di2 front derailleur is a relatively simple task. You mount it to the frame, connect the EW-SD50 electric wire, set up your high- and low limit screws and you’re set to go. Except when you’re not. Sometimes…. sometimes it just doesn’t work flawlessly out of the box.
While those cases are rare, it is actually possible and really easy to micro-adjust your front derailleur on the go. You can set the top and low limits.
Quick note on initial setup and top limit screw
The initial setup procedure for current generation front derailleurs is to first set the top limit screw, then set the (electrical) low limit and finally set the electrical top limit. While setting the top limit twice may seem a bit over the top, you’re actually doing two different settings.
The top limit screw sets the hard limit (between 0.5 and 1.0 mm) and the electrical top limit adjustment sets the final position (0 – 0.5 mm), allowing the front derailleur to overshift slighty – which is what we want.
Low limit adjustment
Note: Low limit electrical adjustment is only available on current-generation front derailleurs (Ultegra FD-R8050, DURA-ACE FD-R9150, GRX FD-RX815)
Shift the front derailleur to the small chainring and the rear derailleur to the largest sprocket.
Now press and hold the button on your junction box A until the LED next to it lights up red. This will take about 5 seconds. You have now entered adjustment mode.
You can use adjustment mode to set the clearance between the chain and the chain guide inner plate. You’ll want to set the clearance somewhere between 0.25 and 0.5 mm.
Press the shift buttons to move the front derailleur closer towards the big or small chain ring. Do your adjustments and once you’re done just press and hold the junction box button until the red light turns off. You will now leave adjustment mode
Shimano recommend the gap [A-B] is as small as possible: 0 – 0.5mm. They say you should adjust so that there is a clearance of 0 – 0.5mm between the chain and the chain guide inner plate. The adjustment setting will be stored on the bike and normal shifting operation will resume. You should now shift the front and rear derailleur through all the gears and made sure the chain does not rub in any gear. If it does, go back into adjustment mode and tweak the clearance.
High limit adjustment
The process for doing the high limit adjustment is similar to that of the low limit. To begin, shift the front derailleur to the large chainring and the rear derailleur to the largest sprocket.
Press and hold the button on junction A until the LED next to it lights up red. You will now enter adjustment mode again. Use the shifter buttons to set the clearance between 0.25 and 0.5 mm. When you’re done just press and hold the junction A button to leave adjustment mode.
Di2 generation differences
While current and previous generation Di2 series have a lot in common, there are some differences too. Electrical low adjustment is only available on current-generation front derailleurs, while the previous generation front derailleurs only allow for electrical top adjustment.
Also, the older Ultegra 6870 and DURA-ACE 9070 series front derailleurs have both a high and low limit adjustment bolt and 25 steps of electrical adjustment (12 each direction) – the newer GRX, R8050 and R9150 front derailleurs feature only one adjustment bolt (top) and 37 steps of electrical adjustment (18 each direction).
Note that this is not the only way to micro-adjust your front derailleur. You could also connect your bike to your Windows computer and use the e-Tube project software to adjust your derailleurs.
And yeah… you could do the method mentioned in this post while riding your bike.. but good luck to anyone attempting to carry a laptop, ride their bike and adjust their front derailleur at the same time!