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Di2 Thread

Old 08-28-16, 10:14 AM
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Originally Posted by colotandem
Alex is the man! He is ALL things MTB tandem and just an all around good guy. I think he's the primary US distributor for Middleburn.

Sounds like lots of possibilities with these cranks! I like having another option that is NOT square taper.
Sadly this option maybe short lived as it looks like Middleburn have gone out of business (I have posted the story separately on this forum). Retailers here in the UK don't seem to be showing any non-square taper tandem cranks in stock. I am hoping that if the story is true that someone else will take on the designs. I was planning on specing the Middleburn modular cranks on a tandem project for 2017.....
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Old 09-13-16, 08:19 AM
  #27  
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Originally Posted by BNB
Thanks for the analysis, @mtseymour.

We would have to leave our ego at home to go with anything less than 4.7 (52-11). We originally only had a 12 highest gear cog on the cassette and would get dropped by single bikes because we were spun out. We like to ride fast downhill so 4.7 is a must. Plus, those single cyclists depend on us to pull fast on the downhill (we are too light to rely on weight).

It's sort of amusing to think we like >12% grades. I suppose we do in a masochistic sort of way, but reality is that these grades are a part of the every-day rides that we do. 15% is not at all unusual.

I think a triple is necessary for us for the best resolution in shifting.

I do like the idea of keeping our FSA cranks as I've looked at the others and too many drawbacks as far as I can tell (questionable BB with Lightning and I'm no fan of proprietary gear; old-fashioned looking cranks with daVinci though I would seriously consider them as I actually don't mind square taper axle and weight seems good; what's with Middleburn's website?? what little I can find on them is not impressive.)
Perhaps you need to work on a higher cadence. 50x11 army 120 rpm is 43 mph.

Above that kind of speed, it's typically more efficient to tuck and coast. Hammer the 50x11 at the top, then take advantage of the momentum and you should be plenty fast with a 50x11
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Old 11-01-16, 12:30 PM
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eTap

Teaser here - this is happening!

I hope to have the bike back from an updated paint job and put it all back together soon - in a different configuration all together.

etap.jpg
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Old 11-01-16, 02:51 PM
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When I decided to go to electronic shifting on our new tandem, I automatically went with Ultegra Di2. I never considered SRAM.

Now with most everything, I assume there are advantages & disadvantages to each. Is there a thread on the tandem forum that makes a comparison (particularly with respect to tandem application)?
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Old 11-01-16, 03:19 PM
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Originally Posted by oldacura
When I decided to go to electronic shifting on our new tandem, I automatically went with Ultegra Di2. I never considered SRAM.

Now with most everything, I assume there are advantages & disadvantages to each. Is there a thread on the tandem forum that makes a comparison (particularly with respect to tandem application)?
I think it's too new to have that thread. I found some comparative reviews - probably not many unbiased reviews and none that I have found related to tandem specifically.

My take on it is this. I like new technology. I like the simplicity (no wires). I've been a big user of Sram for some time now. I've heard that the way that the shifters work is VERY intuitive (we'll see).

Will it be very different than Di2? Who knows... But it will be difficult to get real world comparisons because most users will choose one or the other (its binary). It will be a small sampling of users that will try both and a MUCH smaller sampling that will try both on a tandem.

I've been eyeing the electronic shifting since we commissioned our new tandem frame back in 2012. I was unsure about moving from 3x to 2x, so I built it with 2x mechanical to see if I'd be ok with the wider range cassette (larger jumps in number of cog teeth). I have been very happy with the 2x and wanted to make the move to electronic.

I almost bought some close out Ultegra Di2 bits last year, but never pulled the trigger. I'll post some detailed review of my experience when the time is right, but it will surely be biased.

More to come...
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Old 11-02-16, 07:08 AM
  #31  
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In my experience Di2 is not intuitive. The shift up/down buttons are arranged the same way as my single. Also, they can be reassigned in any arrangement.

Whenever we get on the tandem I shift the wrong way fairly frequently until I get used to it. This becomes less frequent the longer we are on the bike but I still find myself having to think about how to shift all the time. I can't think of another arrangement that would seem more intuitive to me.

Somehow with mechanical shifters, my primitive brain understands that shifting to a larger cog requires pulling a cable and shifing to a smaller cog requires releasing the cable. I can adapt to this on 4 different mechanical shift systems almost immediately and without thought. But I still have to think about shifting with the electronic system and often mis-shift. I don't know why this is.

The Di2 display has helped but it is not a perfect aid because the display for the chainrings is very small. I wear polarized sunglasses that are not bi-focal so I can really only see the cassette indicator and the battery status.

I'll be interested to hear how you like the SRAM setup.
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Old 11-02-16, 08:46 AM
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Originally Posted by colotandem
I think it's too new to have that thread. I found some comparative reviews - probably not many unbiased reviews and none that I have found related to tandem specifically.

My take on it is this. I like new technology. I like the simplicity (no wires). I've been a big user of Sram for some time now. I've heard that the way that the shifters work is VERY intuitive (we'll see).

Will it be very different than Di2? Who knows... But it will be difficult to get real world comparisons because most users will choose one or the other (its binary). It will be a small sampling of users that will try both and a MUCH smaller sampling that will try both on a tandem.

I've been eyeing the electronic shifting since we commissioned our new tandem frame back in 2012. I was unsure about moving from 3x to 2x, so I built it with 2x mechanical to see if I'd be ok with the wider range cassette (larger jumps in number of cog teeth). I have been very happy with the 2x and wanted to make the move to electronic.

I almost bought some close out Ultegra Di2 bits last year, but never pulled the trigger. I'll post some detailed review of my experience when the time is right, but it will surely be biased.
Based on my experience with mechanical SRAM Red, I would expect eTap and Di2 to be very close in shifting performance. The advantage of eTap is that it's wireless (for simpler installation and S&S frames), and mis-shifts are less likely (only 1 button per lever). Di2 has longer battery life and 2017 Ultegra/Dura Ace will have synchronized shifting, multiple shift buttons and junction boxes. Can't go wrong with eTap or Di2.

Let us know how you like eTap.
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Old 11-02-16, 09:47 AM
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Originally Posted by oldacura
When I decided to go to electronic shifting on our new tandem, I automatically went with Ultegra Di2. I never considered SRAM.

Now with most everything, I assume there are advantages & disadvantages to each. Is there a thread on the tandem forum that makes a comparison (particularly with respect to tandem application)?


I have Dura-Ace Di2 on my single while my wife has eTap on hers.


We are currently having a tandem built with Di2.


My impressions:


Shifting performance is excellant with both, though the SRAM drivetrain is noisier.


With the announcement of the wide-range WiFli derailleur for eTap, specified rear cassette ranges is now identical vs. Ultegra Di2. Specified chainring sizes have always been identical.


There's a healthy and growing experience base with workable cassettes outside the specified range for Di2 (11-36 or 11-40 using Wolf Tooth or other products), but eTap is too new. The only datapoint I know of is a user who is successfull using a 11-32 cassette with a stock Red eTap deraillur (Not WiFli version).


Minor hassle with eTap on need to disconnect batteries prior to flying or driving the bike somewhere to avoid battery draindown. Not a big deal in my book.


Di2 seatpost battery replacement (if ever necessary) is a bit of hassle compared to simple battery replacement in eTap.


Battery life with either system is a non issue unless you are a real mega-miler.


Additional hardware required for wireless communication between Di2 and Garmins (or similar). No hardware necessary for eTap.


Di2 is relatively mature product (3rd iteration of Dura-Ace, 2nd iteration of Ultegra, 1st iteration of XTR), eTap will likely be rolling out new products to fill different niches for some time.


Just my random thoughts....
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Old 11-02-16, 09:50 AM
  #34  
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XT or XTR DI2 rear and bar end front?

Couple of questions for those of you who have been there, done that.

Has anyone tried or looked into using DI2 XT or XTR only for the rear and sticking with barends or a brifter for the front shifting? It would appear this dodges the need to fudge the triple or have to convert to a double (admittedly without getting all the benefits of DI2)

How big or little a pain is it to take Di2 apart for a coupled travel tandem?

Regards,

Larry
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Old 11-02-16, 09:56 AM
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Originally Posted by Lorenzo
Couple of questions for those of you who have been there, done that.

Has anyone tried or looked into using DI2 XT or XTR only for the rear and sticking with barends or a brifter for the front shifting? It would appear this dodges the need to fudge the triple or have to convert to a double (admittedly without getting all the benefits of DI2)

How big or little a pain is it to take Di2 apart for a coupled travel tandem?

Regards,

Larry
While using a mechanical front derailleur allows one to do a 3x drivetrain, it also eliminates one of the biggest advantages of electronic shifting: With Di2, front shifts are effortless.
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Old 11-02-16, 10:39 AM
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You are absolutely right - however based on what I've read in this thread it does appear to require some compromises to gearing unless you want to get creative (as some of you clearly have!)

Given our front shifts well enough, our rear does not, and I want to keep my 130 GI top end (53x11) and 19 GI bottom (26x36), a manual front and DI2 XT rear seemed like a simple course of action. Assuming it works, it gives me what I want now with the potential to go all electronic if your brilliant hacks become mainstream.

Plus I'm a cheap so and so and if I can get away without buying a DI2 front derailleur for now... ;-)
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Old 11-02-16, 10:41 AM
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I agree regarding bar-end shifters. Our older bike has bar-end shifters & they work great. Maybe not as technique-free as Di2 but they are a good compromise.
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Old 11-02-16, 11:53 AM
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Originally Posted by Lorenzo
Given our front shifts well enough, our rear does not, and I want to keep my 130 GI top end (53x11) and 19 GI bottom (26x36), a manual front and DI2 XT rear seemed like a simple course of action. Assuming it works, it gives me what I want now with the potential to go all electronic if your brilliant hacks become mainstream.

Plus I'm a cheap so and so and if I can get away without buying a DI2 front derailleur for now... ;-)
If you want prefer a mechanical front derailleur (for triple road crank), it's better to go with Ultegra Di2 rear derailleur. The RD-6870 derailleur can handle a 36T cassette (w Wolftooth Roadlink), and the matching ST-6870 shifter (R) is more ergonomic than adding a XT rear shifter. Ultegra Di2 components are also easier to find on eBay than Di2 XT or Di2 XTR parts.

There's only one eTube wire from the front Junction A to the rear Junction B. If your frame and BB can handle internal routing, the TL-EW02 E tool can easily disconnect and re-connect the wire in the boom tube. The trick is to get the wire pass the front and rear BB shell (usually via slots or holes).
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Old 11-02-16, 02:04 PM
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Originally Posted by mtseymour
If you want prefer a mechanical front derailleur (for triple road crank), it's better to go with Ultegra Di2 rear derailleur. The RD-6870 derailleur can handle a 36T cassette (w Wolftooth Roadlink), and the matching ST-6870 shifter (R) is more ergonomic than adding a XT rear shifter. Ultegra Di2 components are also easier to find on eBay than Di2 XT or Di2 XTR parts.

There's only one eTube wire from the front Junction A to the rear Junction B. If your frame and BB can handle internal routing, the TL-EW02 E tool can easily disconnect and re-connect the wire in the boom tube. The trick is to get the wire pass the front and rear BB shell (usually via slots or holes).
Good to know Ultegra RD can handle a 36T Cassette. I was thinking we would use Ultegra shifters regardless as I thought I read here they would shift XT and XTR. Moot I guess if the Ultegra RD will work and components being easier to find is important;-)

There's no room in the eccentric shell for wiring AFAIK. How feasible is it to run the wiring using the guides for the existing RD cables? (apologies if the question shows a startling ignorance of how DI2 works and what is required to install it;-)
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Old 11-02-16, 02:27 PM
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Originally Posted by Lorenzo
There's no room in the eccentric shell for wiring AFAIK. How feasible is it to run the wiring using the guides for the existing RD cables? (apologies if the question shows a startling ignorance of how DI2 works and what is required to install it;-)
It's possible to use external cabling for Di2, as Shimano offers an external battery option. However, external Di2 cabling is not ideal because of exposure to dirt, moisture, and snags. Here's an Velonews article on external cabling:

Technical FAQ: Installing electronic shifting on a bike without internal cable routing | VeloNews.com
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Old 11-02-16, 03:38 PM
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Awesome - thx all.
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Old 11-02-16, 04:13 PM
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Originally Posted by Lorenzo
Good to know Ultegra RD can handle a 36T Cassette. I was thinking we would use Ultegra shifters regardless as I thought I read here they would shift XT and XTR. Moot I guess if the Ultegra RD will work and components being easier to find is important;-)

There's no room in the eccentric shell for wiring AFAIK. How feasible is it to run the wiring using the guides for the existing RD cables? (apologies if the question shows a startling ignorance of how DI2 works and what is required to install it;-)
it is pretty easy to route around a number of eccentrics and if not with your existing it is an easy swap for eccentrics on most tandems. I use a bushnell featherweight and there is more then adequate room you just have to be careful when removing or installing to not pinch the wire. the di2 wire is only 2mm thick and the ends are only about 3.5 thick and use a 6mm hole if you want to use a Shimano grommet. I usually cut the holes smaller and you can still use the grommets and they come in two shapes. I have routed the wires internally on a number of bikes that were not DI2 ready and the tandems are not really any different save you need longer wire runs.
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Old 11-02-16, 05:03 PM
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Thx - I'm planning to pull it soon (it's a Phil Wood) as part of winter maintenance so I'll take a closer look. There is a hole already at the back of the stokers BB, so assuming I can get the wires into the Captains downtube, and over/under the eccentric, and the junction box fits in the boom tube ... ;-)
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Old 11-02-16, 05:35 PM
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Once you remove your BB, you can see how Junction A, Junction B, internal battery, and rear derailleur will be connected. There are many how-to videos on internal Di2 wiring.

Unfortunately, wireles eTap won't work with a single shifter (for rear derailleur).
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Old 11-03-16, 09:12 PM
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It looks like there is another option on Kickstarter for electric shifting. I'm not associated with this in any way, it just looks interesting.

Last edited by cb400bill; 11-20-16 at 04:43 AM. Reason: Removed crowd sourcing link
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Old 11-03-16, 11:56 PM
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Originally Posted by New2Two
It looks like there is another option on Kickstarter for electric shifting. I'm not associated with this in any way, it just looks interesting.
This "electric" system has two fundamental flaws. First, it relies on cables to move the mechanical derailleurs. The cables and derailleurs are subject to wear and contamination. Unlike Di2, EPS, and eTap, the Xshifterwill drift out of alignment over time. This cable-actuated system won't come close to the speed of real electric shifting (esp at the front derailleur).

The other problem is the Xshifters won't integrate with existing road shifters. At high speed (or in traffic), it's dicey to take a hand off the hood to make a shift. It will also be easy to mis-shift because each shifter has 4 buttons with different functions. Although mtn bikes use separate brakes and shifters, this system lacks the electric motors that can power through dirt and muck for consistent shifts.

Why spend more money when it won't improve on a good mechanical drivetrains like Ultegra or XT?

Last edited by cb400bill; 11-20-16 at 04:43 AM. Reason: Removed crowd sourcing link
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Old 11-04-16, 06:44 AM
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I wouldn't use it on our road tandem, but I might look at it for a hybrid tandem...after it has been out a while.
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Old 11-04-16, 09:04 AM
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Each removable battery and motor weighs over 110g and must be mounted to the seatstay or bottom of the downtube by two zip ties. It will be very difficult to get a firm and reliable fit because frames use wide range of shapes and sizes. With each shift, there will be a lot of pressure on the battery/motor assembly to shift out of position. Rough roads or technical singletracks will also knock the Xshifter out of alignment. Once this happens, you'll probably have to replace the zip ties and dial-in the indexing. Not exactly fun in the middle of a long ride or while touring. It doesn't help that the seatstay and downtube are exposed to a lot of moisture and dirt. Maybe this is why the demo was done on a Shimano Acera 8 or 9 sp derailleur, rather than a 10 or 11sp drivetrain.

It should be noted that the biggest advantage of Di2, eTap, EPS is the fast and reliable front shifting. These systems are very reliable because the front derailleur moves quickly and intentionally over-shoot, but retract slightly to keep the chain on the right ring. The Xshifter can't do this.

The Xshifter also only works on half of the shifts, when downshifting to a larger rear cog, or upshifting to a larger chainring.
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Old 11-04-16, 03:35 PM
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Originally Posted by mtseymour
Each removable battery and motor weighs over 110g and must be mounted to the seatstay or bottom of the downtube by two zip ties. It will be very difficult to get a firm and reliable fit because frames use wide range of shapes and sizes. With each shift, there will be a lot of pressure on the battery/motor assembly to shift out of position. Rough roads or technical singletracks will also knock the Xshifter out of alignment. Once this happens, you'll probably have to replace the zip ties and dial-in the indexing. Not exactly fun in the middle of a long ride or while touring. It doesn't help that the seatstay and downtube are exposed to a lot of moisture and dirt. Maybe this is why the demo was done on a Shimano Acera 8 or 9 sp derailleur, rather than a 10 or 11sp drivetrain.

It should be noted that the biggest advantage of Di2, eTap, EPS is the fast and reliable front shifting. These systems are very reliable because the front derailleur moves quickly and intentionally over-shoot, but retract slightly to keep the chain on the right ring. The Xshifter can't do this.

The Xshifter also only works on half of the shifts, when downshifting to a larger rear cog, or upshifting to a larger chainring.
There is some incorrect information here about XShifter that I'd like to correct. First of all the servo does not rely on zip ties to maintain position. All the load is taken up in the Bowden cable. We have a video that demonstrates this on the Kickstarter page. Regarding shifting speed, it is as fast as di2 and eTap. We demonstrate the repeatability of within 2 microns. We are planing a significant speed improvement. Over shifting, XShifter has that capability on both front and rear. Furthermore, the user can tune the amount and timing if they like. No other system offers this flexibility. Please go to our Kickstarter page for all details.
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Old 11-05-16, 12:06 AM
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Originally Posted by XShifter
There is some incorrect information here about XShifter that I'd like to correct. First of all the servo does not rely on zip ties to maintain position. All the load is taken up in the Bowden cable. We have a video that demonstrates this on the Kickstarter page. Regarding shifting speed, it is as fast as di2 and eTap. We demonstrate the repeatability of within 2 microns. We are planing a significant speed improvement. Over shifting, XShifter has that capability on both front and rear. Furthermore, the user can tune the amount and timing if they like. No other system offers this flexibility. Please go to our Kickstarter page for all details.
We're getting off topic, but let's discuss errors and omissions since you're soliciting funds.

Use of Zip Ties
While the Bowden cable may maintain derailleur position in ideal conditions, the zip ties are less secure than bolt fasteners. On a 10 or 11sp drivetrain with tighter spacing, small movements in the battery assembly may be enough to affect indexing. Why use 8 or 9sp Acera drivetrain for your demo?

Shift Speed
The XShifter only provides electric assist in one direction (ie while pulling cable), and will be affected by dirty cables or sticky derailleurs. The XShifter can't provide faster shifting when for rear downshifts (large cog to small cog), or front upshifts (granny to big ring). It's hard to believe that the XShifter will match the speed of Di2 or eTap for all shifts, under full load (200-300 lb rider or tandem team), and in inclement conditions.

Poor Ergonomics
Most road bikes are equipped with STI-type shifters (aka brifters). The XShifter requires a road rider to move one hand from the brake hoods to the top bar shifter. This is not a good idea at high speed or in heavy traffic. On a mtn bike, the Shimano & SRAM trigger shifters make it easy to distinguish between an upshift of downshift. It's much harder to press the right button on the XShifter (1 of 4 positions), especially on bumpy terrain.

Protection from Water and Debris
The XShifter batteries are located in the dirtiest part of the frame: bottom of the downtube and the seatstays. For mtn bikers, the downtube location is vulnerable to rock damage. In contrast, most Di2 and EPS riders use internal wiring with the battery safely inside the seatpost. The eTap battery is integrated into the derailleur, so it's fairly protected. For the minority using the Shimano external battery, it's safely tucked away on top of the downtube (away from dirt, water, and debris). Not only is the Shimano external battery safely tucked away, it only has one small connector for the eTube wire. I have less confidence that the XShifter battery will stay dry when pounded by water at the USB charging port and removable battery interface interface.

Fast, Reliable Front Shifting
Di2, EPS, and eTap have powerful motors that can pull the chain in either directions for front shifts. The XShifter can only provide electric assist in one direction (ie. pulling cable instead of pushing cable). When shifting from the granny to the big ring, the XShifter must rely on the derailleur's cable tension to stop the cage from moving too far. When shifting from the big ring to the granny, the XShifter can't provide any electric assist. Your website video is misleading because it shows the front derailleur shifting a close-ratio triple crankset in a kick-stand while the crankarm is slowly rotated by hand at about 30 rpm. Virtually any derailleur will shift well in these conditions. It's a different story for double cranket (w 16T gap) under full load at more than 90 rpm with cable stretch or a dirty drivetrain.
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