Can’t shift to smallest sprockets when in small ring? Adjust Gear Position Control
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
- Prevent the chain rubbing on the inside of the big chainring. In some cases the chain can even catch the big ring's shift ramps.
The second point is especially true for modern disc bikes with relatively short chain stays. Those generally 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.
Does your version of Di2 have Gear Position Control?
Whether or not your version of Di2 has Gear Position Control depends on its generation and firmware version.
Generally speaking, if the difference between the front chain rings is 14T then you can configure GPC. If it's 16 or greater then Gear Position Control is enabled and not configurable.
These versions of Di2 have Gear Position Control:
11-Speed Ultegra R8050, Dura-Ace R9150, and GRX RX810
All three last generation Di2 road/gravel series feature Gear Position Control.
On bikes with a front difference of less than 16T you can configure GPC in E-Tube Project. If the front difference is 16T or greater, GPC will be enabled by default and you cannot override that setting.
12-Speed Dura-Ace
Gear Position Control can not be disabled when using 52-36 or 50-34 chain rings.
If you're using the 54-40T chain rings then you can switch Gear Position Control on or off as you see fit.
12-Speed Ultegra / 105
These groupsets do not have Gear Position Control - the feature is disabled by default, and can not be enabled.
12-Speed GRX RX825
Gear Position Control can not be disabled when using the 48-31T 2x crankset.
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.
E-Tube Project V4 / V5
If you're using either version 4 or V5 (Professional) of E-Tube Project, connect the charger (V4) or the SM-PCE02 (V4 / V5) to the bike and start the software.
After connecting to the bike, open the Customize screen and click the Synchronized Shift option on the left.
You can now switch off (or on) Gear Position Control. Once you're done, click the Apply button at the bottom left.
E-Tube Project 3.4.5
Are you using E-Tube Project 3.4.5 or older? This is how you disable Gear Position Control:
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. You will only be able to change Gear Position Control with 53 - 39 chainrings selected.
And yes, you can trick the Di2 system and tell it you're using a different crankset than you're actually using, but be aware that doing so would void warranty, and can result in a setup that is out of spec - not tested by Shimano, and not guaranteed to work.
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.
