I've been thinking about Di2.
The new 11 speed shifters will work with older 10 speed rear mech. The shifters are sending an up or down signal to the mech. The shifter has no knowledge of the position of the rear mech. The rear mech manages the autotrim for the front mech and I’d be very surprised if you needed to match the F&R mechs but I couldn’t say 100%.Posted 4 years ago
Inspired by the recent disc brake release really. However, I was reading that they’re an 11 speed shifter.
What makes them 11 speed? Surely, it’s just an up and down button with nothing in there that makes it 11 speed?
Where’s the “brain” in electronic shifting? The bit that says how much for each button press and when to stop?
Have people started “hacking” these yet? Surely a bit of software tinkering could make it 9 speed or any speed you want.
Or am I mad?Posted 4 years agoIanMunroMember
The shifter has no knowledge of the position of the rear mech.
I’m not entirely sure that’s true. I think once the shifter places a shift command out on the bus, the mech will respond with what sprocket position it’s at. Whether the shifter makes any use of this data is a different matter though.Posted 4 years ago
I’m not entirely sure that’s true. I think once the shifter places a shift command out on the bus, the mech will respond with what sprocket position it’s at. Whether the shifter makes any use of this data is a different matter though.
Interesting, the thing is, I’m not convinced that the rear mech even knows what gear it’s in! If you use the micro adjust to shift the chain to a larger sprocket (without actually shifting the mech using the button), I think you can still run through all the gears until the mech hits the limiters. This would lead me to believe the shifter just shifts either up or down until it hits the stops. I messed around with this a while ago and can’t say for sure this was the case but I might try it tomorrow.
Actually, thinking more on this, I suspect the rear mech must know roughly where it is in order to work the auto trim……Posted 4 years ago
I just had an email from my Shimano guy in Japan….
For the OP, the new Ultegra shifter with hydraulic cylinder (ST-R785) is compatible with ALL e-tube drivetrains, so Dura Ace 9070, Ultegra 6870 and 6770, as well as Alfine Di2. 10 speed or 11 speed. You *may* need to upgrade the firmware to make all this work.Posted 4 years agoIanMunroMember
Actually, thinking more on this, I suspect the rear mech must know roughly where it is in order to work the auto trim……
As it happens I’ve got the electronic guts of an ultegra rear mech sat in front of me 🙂 I bought a 2nd hand one off ebay so as to find out what’s in it.Posted 4 years ago
Looks like there’s one method of establishing position – a potentiometer on the output shaft, and another method for establishing the rate of movement and possibly fine scale movement – an optical shaft encoder near the motor.
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