Every now and then I get some messages from users unable to shift into the smallest sprockets (sometimes cogs). Most users are concerned that their new Di2 is malfunctioning, but that is not the case. In this post I’ll explain Gear Position Control as found on bikes equipped with Ultegra R8050, DURA-ACE R9150 or newer.
Note that Gear Position Control is not enabled on 12-speed Ultegra/105 derailleurs. If you're on 12-speed Ultegra/105, you can shift into the smallest cassette cogs when you're in the small ring. There is no way to change this setting.
Gear Position Control
So what is Gear Position Control, exactly? Basically, it is Shimano’s way to prevent cross chaining when in the small ring. They do this for two reasons:
- Prevent a chain line that would lower the chain tension too much
- To accommodate modern disc bikes with shorter chain stays that don’t work well with extreme cross chaining
Shifting to the small ring when in the small sprockets
*Gear Position Control *does not just affect your shifting when you’re already in the small ring – it also changes how your bike shifts from big to small chain ring.
When your rear derailleur is in the smallest sprockets (colored blue in the image above) and you attempt to shift from the big to the small chain ring you will notice that it does not shift the front derailleur. Instead, the rear derailleur will shift down two gears.
When the rear derailleur is outside this range shifting will function as normal. Shifting from big to small ring will actually shift the front derailleur to the small ring.
Note that the range depends on your rear derailleur and selected chain rings. For example, on mountain bikes the range is smaller when using a small cage rear derailleur and larger when using a medium/large cage derailleur.
How to disable Gear Position Control
Most people tend to avoid cross-chaining as much as they can so you may never have experienced this issue yourself. Still, sometimes it is nice to be able to shift to the smallest sprocket no matter the chain ring you are in – when taking out the rear wheel for example.
Fortunately Shimano made the Gear Position Control a setting you can change yourself. To change this setting you’ll need to use the e-Tube application to connect your bike to a Windows computer.
After making the connection click Customize and then the Shift Mode Setting button. On this screen, you can change the Gear Position Control. To disable it, select “do not set“. To enable it, select “set“.
Note that this setting may or may not be available, depending on the derailleurs and chain rings you have installed/selected.
Complete the setup
Once you’re happy with the setting just click Next and Back to get back to the main screen. Then click the Complete Setup button to save the settings to the bike and close the connection.