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PostPosted: Wed Nov 29, 2017 7:35 pm 
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Posts: 48
Hey all,
is there a way to allow di2 to cross chain (small/small)? I currently cannot be in the small ring up front and be in either of the smallest cogs in the rear.
I want my 22 gears!!! help!


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Posted: Wed Nov 29, 2017 7:35 pm 


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PostPosted: Wed Nov 29, 2017 7:41 pm 
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No. Unless you space the chainset out by a couple of mm.
Then the shifting at the other end will be dire. And you don't have 22 gears. You effectively have two ranges of gears that overlap massively in the middle.

Try looking at a ratio chart for your set up. See how many duplicates you have.


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PostPosted: Wed Nov 29, 2017 8:11 pm 
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If I'm not mistaken this is the default setup for 52\36 setups but can be changed to 53\39 through e-tube which should allow for cross chaining. If I'm not mistaken ...

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PostPosted: Wed Nov 29, 2017 8:43 pm 
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Why are folks so afraid of front derailleurs?


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PostPosted: Wed Nov 29, 2017 9:45 pm 
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Location: Houston, Texas
il professore wrote:
is there a way to allow di2 to cross chain (small/small)?

The only way is to connect the shifters to the E-Tube application and set the chainrings to 53/39, 52/38, 50/38, 46/36 - i.e a chainring combo with a 16-tooth difference or something like that.

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PostPosted: Wed Nov 29, 2017 9:47 pm 
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Ah. Di2 physically won't let you shift into a cross chained gear where rubbing will occur.

Sounds eminently sensible.


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PostPosted: Wed Nov 29, 2017 10:03 pm 
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mattr wrote:
Ah. Di2 physically won't let you shift into a cross chained gear where rubbing will occur.

Sounds eminently sensible.



That's the way you should shift even on a mechanical group.

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PostPosted: Wed Nov 29, 2017 10:08 pm 
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Joined: Sun Jan 09, 2005 5:14 pm
Posts: 462
Location: Sunny So Cal
The question is do you actually want to cross chain? I'm running 52/36 and 11-30t on my bike and found Shimano's default setup annoying during my first couple rides just because I know it's there. Now I don't even remember the no cross chain setup after clocked over 1,000 miles on the bike because I just don't use those gearing combos as good habit.


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PostPosted: Thu Nov 30, 2017 4:56 am 
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Sound like a good thing. Can't for the life of me figure out why anyone would choose to be in small-small?


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PostPosted: Thu Nov 30, 2017 7:27 am 
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wheelbuilder wrote:
Sound like a good thing. Can't for the life of me figure out why anyone would choose to be in small-small?


To expand on this, I generally wants to stay in the big ring as long as possible. 2x4 is the very extreme end of acceptable for chainlines before I decide to "syncro-shift" down to 1x5. In the opposite direction. I will go to 1x7 before syncro-shifting to 2x5. This is with a Shimano 11-28t and SRAM 11-30/32t cassettes. I would not use a SRAM 11-28t because the gear spacing is silly.


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PostPosted: Thu Nov 30, 2017 8:20 pm 
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wheelbuilder wrote:
Can't for the life of me figure out why anyone would choose to be in small-small?


Going down a steep hill in high gear, big ring and little cog. Get to the bottom and it immediately, ten feet, starts going up the next hill. Easy and simple to just drop from the big ring to the small ring and you are in the perfect gear. That drops you 3 or 4 gears and is just right for an uphill when you are already going at high speed. Then you quickly move up the cogs as you climb the steep hill. I ride in terrain like this frequently.

Another scenario. You are riding along pleasantly on the flat in the small ring and one of the smaller cogs. You want to go a little bit faster, so you just shift down one cog in back. It happens to be the smallest cog but is the perfect gear for that moment. Easier to do that than shift up to the big ring with the front derailleur and then shift up 3 or 4 cogs on the rear derailleur and hope you find the right gear. I like to ride with cassettes that are straight blocks more or less. Simple and easy to find the next easiest or hardest gear. One click away.

I should add I can cross chain small ring and small cog easily with my Di2 7970 bike. It has 53-42 rings and 12-23 cogset. No rubbing at all.


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PostPosted: Thu Nov 30, 2017 8:49 pm 
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RussellS wrote:
wheelbuilder wrote:
Can't for the life of me figure out why anyone would choose to be in small-small?


Going down a steep hill in high gear, big ring and little cog. Get to the bottom and it immediately, ten feet, starts going up the next hill. Easy and simple to just drop from the big ring to the small ring and you are in the perfect gear. That drops you 3 or 4 gears and is just right for an uphill when you are already going at high speed. Then you quickly move up the cogs as you climb the steep hill. I ride in terrain like this frequently.

Another scenario. You are riding along pleasantly on the flat in the small ring and one of the smaller cogs. You want to go a little bit faster, so you just shift down one cog in back. It happens to be the smallest cog but is the perfect gear for that moment. Easier to do that than shift up to the big ring with the front derailleur and then shift up 3 or 4 cogs on the rear derailleur and hope you find the right gear. I like to ride with cassettes that are straight blocks more or less. Simple and easy to find the next easiest or hardest gear. One click away.

I should add I can cross chain small ring and small cog easily with my Di2 7970 bike. It has 53-42 rings and 12-23 cogset. No rubbing at all.

Fair enough. I ride and shift differently, and as a mechanic I try avoid "and advise my customers to avoid" operating in the extremes of the drivetrain. Your scenario makes sense though. Thanks for the info.


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PostPosted: Thu Nov 30, 2017 9:47 pm 
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Personally, given the choice (which Shimano doesn't anymore) I like having all combinations available to me all the time. While I don't particularly like @RussellS's scenario of dropping to the small ring when you're in the small cog and big ring there are numerous other scenarios where a "bad gear combination" might be preferred, albeit just for a very brief time. And in @RussellS's case, if that's what he likes then why limit him. I'm sure he doesn't ride cross chained on a regular basis or for any length of time. He is conscious of what he is doing and fully aware of the pitfalls, but for that brief scenario, it's a welcome option. However, there are people, probably not many if any on this site, that don't realize anything about the pitfalls of crosschaining and so Shimano, rather than require these people to attend a course called "Shifting for Idiots" has, in their wisdom, just designed a system where the "Shifting for Idiots" course is not required. Yay, for the idiots. But I like to decide for myself how I like to use the gears at my disposal.

Imagine for a second if the current state of gears/derailleurs etc. had, from the beginning, never allowed us to cross chain the small ring to the either of the two smallest cogs at the rear. It would be something we just always lived with. Now imagine if a new system came out and was marketed where they said... "Now you have access to those two previously unavailable cogs no matter which chainring you are on". Pretty sure everyone, would go "Awesome!! Now, (in the case of a 36/52 crankset) when I'm cruising along in 36/13 and want just a bit more gear for little while for whatever reason, instead of having to shift to the big ring and shift up to the 17 cog, all I have to do is click into the 12 and voila, I'm there. Brilliant!!" (36/12 is pretty much the same gear as 52/17). No one is saying that you should ride in that combo for extended periods, but for those scenarios when you just want a quick snap, it's there much quicker than having to change both the front ring and the rear by several cogs.

Then there is now Synchro Shift and Semi Synchroshift. Aaach... Again, shifting for dummies candidates step right up. Which version would you like?... because you can't have it all, at least not anymore. At what shift points would you like the front to automatically shift for you? Decide now, because if you want different shift points we'll have to hook you up to E-Tube and change things. Or maybe you'd just like the rear to shift automatically when you shift between front rings. Oh, but how many cogs would you like it to shift automatically when you change front rings... 1, 2, 3, or even 4? But you can only choose one of those multishifts, or none, but please decide now cuz we're not hooking you up to e-tube while out on the ride.
Big/Big is another useful combo, say when cresting a slight hill that wasn't steep enough to drop into the small ring for that last little bit. And while that combo is available in non-synchro mode, it is not available in Synchroshift by default... you have to again go into E-tube to allow that.

Now, comparing this to my Campy Mechanical (and this is not a campy/shimano discussion, simply a shifting discussion)...
Every combination and every scenario that is available in either Synchroshift, or Semi-Synchroshift, or Non-Synchroshift is always at my disposal, instantaneously. Simulataneous shifts front and rear as fast as I can think it... and the choice of how many rear cogs I want to move along with the front shift is totally up to me, right there and then... again, so fast, and so easy. It's about being familiar with your bike and how to shift it. And every combo is available to me without any rub, either on the front derailleur or on the inner side of the big chainring when crossed in small/small, although I admit small/small is a combo I never use, but the point is I could and it would work.

Just more food for thought... Is Synchroshift an innovation?...Yes. Is it an innovation that makes riding your bike more or less pleasant and/or efficient? The answer is not so clear. For me it is definitely No.

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PostPosted: Thu Nov 30, 2017 9:53 pm 
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So this kinda goes back to what others have said, but what does Di2 see you're rings as? We know that 53/42 rings work on the 7970, I can attest to 50/36 working on 6870. But as others have said, if you're running (or have Di2 configured as) 52/36, 50/34, etc, you probably won't be able to.

Do you have the Ant+/Bluetooth transmitter or the PC interface so you can go in and change the settings?


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Posted: Thu Nov 30, 2017 9:53 pm 


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PostPosted: Thu Nov 30, 2017 10:41 pm 
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@IrrelevantD: yes, you can “fool” it by saying your rings are different than they are.
But regardless of which interface you use to be able to go in and change the settings, my ultimate point is that I have every single option available to me all the time without any synchroshift or semi synchroshift or non-synchroshift, without ever having to change or modify any settings.

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C59 Five Years Later
My Special Colnago EPQ
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