7

Are there any road bike electronic shifting systems out there currently that only have a single up and down shifter lever and use a computer to make the decision of whether to shift on the rear cassette or the front chainring for you, instead of you having to make that decision yourself? I've heard that some current systems might have failsafes to try to prevent cross-chaining, but as far as I know, these still have the ability for the user to decide for themselves between the front and rear, whereas I am looking for a totally computerized system, where the user is not presented with this choice. If this does not exist yet, is it in the works somewhere? What do you think is the timeframe on such a thing coming to market? What has prevented its inception so far?

3 Answers 3

8

SRAM eTap has a mode for this. It’s called Sequential Shift Mode:

Sequential Shift Mode simplifies the shifting experience by automatically controlling the front and rear derailleur as you upshift or downshift through the gearing range. Using only the left or right shifter buttons, the system controls the shift behavior of both derailleurs to keep the changes in gear ratio smooth and cadence consistent. Pressing one controller makes the gearing easier, the other harder, it’s that simple.

https://support.sram.com/hc/en-us/articles/1260804086189-What-are-Enhanced-Shift-Mode-and-Multishift-and-how-do-I-enable-them-using-the-AXS-Mobile-App-

7

The Shimano di2 system does this if you want. Using their app you can program the buttons to sequential shift 2, which I am using. You can choose where the computer shifts the front chainring and how much it shifts the rear to compensate for the larger shift in the front. I have my right buttons configured this way and the left buttons configured just to shift the front, which is useful when I am coming to a climb. I would rather shift the chainring before the climb rather than on it.

2
  • Though not on the first (with the external battery) and second Di2 generations (early type of internal battery). The more recent type of internal battery has the required programmable controller chip. Connect the etube software to see whether the system is enabled.
    – Carel
    Feb 7, 2022 at 8:14
  • I've got a similar setup with sequential shift 2, using the aux button on the right to force a chainring downshift. This setup gives up the ability to force an upshift, but frees up the whole left shifter, which lets me run a brifter-actuated dropper post on a gravel bike.
    – RLH
    Sep 5, 2023 at 1:29
-4

That would be a terrible idea.

Front shifts are slow, especially if you have large difference between the chainring sizes (like you usually do).

Rear shifts are fast, especially if the cassette is a hyperglide cassette (or some of the newer equivalent types of technology).

The beauty of the current user interface is that you have the ability to decide if you need your shift to be fast, or if it's acceptable for the shift to be slow, by having two shifters you can operate independently.

If there's only one shifter and the computer automatically decides whether to shift front, rear or both at the same time, it may mean you get a slow shift when you absolutely want your shift to be fast.

3
  • 1
    This does not really answer the question. Feb 6, 2022 at 19:07
  • It's true though. Front- and rear shifts are completely different. If the computer selects the front when you expected a rear shift, it can easily lead to the chain coming off and possibly a crash. Vice versa, a safe front shift requires releasing the power briefly before the chain switches, which is just wasting momentum if the shift comes on the rear (where the power should rather be reduced briefly after the shift, when the chain actually comes over the sprockets). Feb 7, 2022 at 22:29
  • Whether its a good idea or not, both SRAM and shimano did design and build them, which is what OP is asking about. Even before that, there were centrifugal-based shifters that could change rear gears for you.
    – Criggie
    Feb 8, 2022 at 9:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.