This guide applies to front road and gravel derailleurs that have one adjustment bolt (or limit screw). You set up the top (high) limit for these derailleurs using the adjustment bolt and set up the low limit electronically. All current generation derailleurs are one-adjustment-bolt derailleurs:

• GRX FD-RX815
• DURA-ACE FD-R9150
• Ultegra FD-R8050

Before your start, make sure you have correctly set up your front derailleur height, angle and support bolt. Have a look at the front derailleur installation guide for information on how to do that.

Adjusting the top adjustment bolt

These current generation derailleurs have only one adjustment bolt, but just like all other Di2 front derailleurs they also have the support bolt. Make sure you adjust the correct bolt. You will need a size 2 hex wrench to set the top adjustment bolt.

The first step is to shift the front derailleur to the large chainring and the rear derailleur to the smallest sprocket.

Next, turn the top adjustment bolt to set the correct clearance between the chain and chain guide outer plate. You’re looking for 0.5 – 1 mm of clearance.

Set the low limit

There may not be a low adjustment bolt, but that doesn’t mean you do not need to set it up. To start, 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. You will now enter adjustment mode. Be sure to release the button on time – if you keep it pressed the rear derailleur protection reset will trigger.

The final step is to set the correct clearance between the chain and the chain guide inner plate. This time you’re looking for about 0.15 to 0.5 mm of clearance (Shimano say 0 – 0.5 mm, but anything near 0 mm would likely cause chain rub).

All three of these derailleurs can move 18 steps inward and 18 steps outward from the initial position (37 steps total). It can be easy to lose track of the current position, but if you find that it doesn’t not move when you press a button you’ve probably gone too far. You can get the current adjustment value by connecting the bike to a windows computer.

Note that when you’re in this adjustment mode the chain guide will overrun slightly and then move back in an exaggerated manner, so that you can check the adjustment direction. When checking the positions of the chain guide and the chain, perform the check after the front derailleur has moved back and come to a stop.

Press and hold the button on your junction A to leave adjustment mode. Now shift the front and rear derailleurs through all gears and make sure chain rub does not occur in any gear. If it does, go back into adjustment mode and tweak the chain clearance.

Set the high/top limit

After setting the Top limit screw and electronically setting the Low limit it is time to finish setup by setting the Top limit electronically. This time however, you’ll have to set the clearance between 0 – 0.5 mm.

To do this shift to the largest chainring and largest cog and then press and hold the button again to enter adjustment mode. Set the clearance between 0 and 0.5 mm and exit adjustment mode.

Setting the limit screw first and then setting the top limit electronically will allow the front derailleur to overshift, to then return to its correct position as set using the electronic limit.

Want to read more about setting the electrical limits? Read more about micro–adjustment on this page.