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How to maintain/adjust Shimano Ultegra DI2 (2018)
This information is available in many videos and forums, but I've collected it here so that I don't have to look it up next time. <h>Chain is rubbing on other gears</h> The DI2 does <i>not</i> adjust itself. It does, however, know how far apart your gears are. Once you've got one gear---a central one---adjusted, the others are automatically correct, as well. The DI2 also almost never needs adjustment (at least in my experience).<fn> If you hear the chain rubbing on any of the gears, then you can use the special <i>adjustment mode</i> to fix it. <ul> Put the bike into the 5th gear (counting from the largest gear). It doesn't matter which gear you use on the front. Press and hold the little button under the sender for 2 seconds to enter "adjustment mode". Press the small shifter on the right-hand side to move 1/12 of a position (0.2mm) toward smaller/harder gears Press the large shifter on the right-hand side to move 1/12 of a position (0.2mm) toward larger/easier gears </ul> Adjust until the rubbing stops.<fn> You can also do this while you're riding if you still notice an issue. It's quite easy to get on a flatter, more-open stretch, shift to the central gear, go into adjustment mode and adjust until the rubbing is gone. <h>Lowest gear does not "hold"</h> If you put it into the lowest gear and you hear the DI2 buzz, it is thinking about downshifting automatically because it has detected a problem. Generally, you'll turn once or twice and it will drop back into the second-lowest gear. This is all the more annoying because when you need the lowest gear, you generally <i>kinda need the lowest gear</i>. There are two possibilities. <h level="3">Bent bracket</h> The bracket holding your derailleur on the frame is bent. This can happen if you hit it hard enough against something. The bracket is designed to bend; if it didn't, then the carbon frame might crack first. Replacing a bracket is cheaper. You can generally see if the bracket is bent. If it's bent, you can bend it back into place with no issues<fn>. It was at this time that I learned that it's a good idea to keep a spare bracket on hand, just in case. I have one now. Once you've adjusted the bracket back into place, you might need to micro-adjust your gears (see above) in order to get them running smoothly again. <h level="3">Misadjusted lower limiting screw</h> In my case, the bracket was just fine, but the lower limiting screw (marked "L") was touching bottom when in the lowest gear. This pressure cause the DI2 to back off by a gear. A quarter-turn to the left (making it looser) fixed this issue immediately. <ft>The reason I had the pleasure of learning all of this is that, when my bike came back from the mechanic, it was no longer able to stay in the lowest gear. I looked up how to micro-adjust the DI2, which turned out not to be the problem, but it's still good to know.</ft> <ft>I've also seen a video that says to start in the 5th gear, then hit the large shifter <i>until</i> you hear rubbing, then back off by four taps on the smaller paddle. I didn't try this, but it also sounds reasonable.</ft> <ft>A good friend of mine (Hi, Oli) did this for me after the SBB saw fit to throw my bike into a pile of other bikes when we'd exceeded the storage capacity of a dozen-car train (12 bike slots) on the way to a 3000-person cyclosportif. No, no, I wasn't annoyed at all.</ft>