# Ultegra 6800 shifters and DA 7900 derailleurs



## paterberg (Nov 7, 2010)

Will this work? Shimano Ultegra 6800 11 speed shifters paired with DA 7900 10 speed front and rear derailleurs plus 11 speed cassette and chain. Thanks.


----------



## mpcbike (May 12, 2009)

No, it won't.


----------



## Gjash (Jan 17, 2013)

I don't have this setup but the rear should work fine but the front may be problematic because of some change. Please try and let us know. :-D


----------



## mpcbike (May 12, 2009)

See my previous before you waste $$$.


----------



## Gjash (Jan 17, 2013)

can you explain why these 11 speed shifters won't work with the 10 speed derailleurs? The throw distance is determined by the shifter not the derailleur, right?


----------



## mpcbike (May 12, 2009)

Shifter controls only the length of cable pulled per shift. The derailleur design determines how far it will move with the designated amount of cable pull. These ratios and lengths are not the same 5700-6700-7900(10spd) to 9000-6800(11spd). Further complicating the issue 7900 FD is different ratio than either 5700 or 6700. I'd suggest that a 7900 FD with 6800/9000 levers would not even come close to working.


----------



## Gjash (Jan 17, 2013)

This is not correct. I'm using ST-6800 11 speed shifters with 10 speed cassettes without a problem. The distance between sprockets is the same. Shimano just made the 11 speed cogs narrower to fit that extra one. I think the OP should investigate more and I'm tempted to throw a RD-6700 derailleur on just to prove it. I think you may be right with the front, but I believe it can be done, just difficult to get adjusted. Really just have to try it.


----------



## mpcbike (May 12, 2009)

Are you using a 6800 shifter with a 6800 der on 10 speed cassette? 

That will work fine!

That's also a completely different scenario than I was addressing...


----------



## mpcbike (May 12, 2009)

My original claim of "no" comes from trying a 6800 r.der with 6700 shifters/chain/cassette.

No bueno.


----------



## Gjash (Jan 17, 2013)

Interesting. Yeah, I'm using 6800 shifter with 6800 RD with a 10 speed cassette.when you tested this what happened? my guess is the chain is the difference and it would work with an 11 speed chain.


----------



## Gjash (Jan 17, 2013)

mpcbike said:


> Shifter controls only the length of cable pulled per shift. The derailleur design determines how far it will move with the designated amount of cable pull. These ratios and lengths are not the same 5700-6700-7900(10spd) to 9000-6800(11spd). Further complicating the issue 7900 FD is different ratio than either 5700 or 6700. I'd suggest that a 7900 FD with 6800/9000 levers would not even come close to working.


Could someone comment on this? "The derailleur design determines how far it will move with the designated amount of cable pull."

My understanding is that this is determined completely by the shifter and the rear derailleur doesn't care or know about index or throw distance. they're just dumb and respond to the shifters. Could someone confirm?


----------



## mpcbike (May 12, 2009)

Pull ratio, think SRAM vs. Shimano. They use exactly the same gear spacing but are 100% incompatible! Old SACHS derailleurs used to have 2 different cable paths depending on what shifter you were using(shimano/SACHS). Finally if it was only cable pull, every 10 speed system should be interchangeable as the cables would all need to move same amount of Cbl(since cog spacing is exact for the S companies & damn close for campy). But, you cannot mix SRAM, Shimano or Campagnolo 10 SPD rear der's & shifters & make them work correctly.


----------



## Gjash (Jan 17, 2013)

We're just talking Shimano. Bringing in SRAM and Campy complicates and detracts. I'm looking for an answer to what determines throw distance, derailleur or shifter ?


----------



## mpcbike (May 12, 2009)

Derailleur dictates how far it moves with a given amount of cable pull!!!!!!!!!!!!!

Only SRAM has 1:1 ratio & bringing them in was to make an example.

Shifter only "controls" how much Cbl is pulled. How far the cage moves laterally when that cable is pulled is dependent on derailleur design!!!!!

This is not really a question or debatable. It is a basic fundamental of bicycle drivetrains since the advent of indexing.


----------



## Gjash (Jan 17, 2013)

So you're saying there is no way my st-6800 shifters will work with my 6700 RD? That's the question. I think you're wrong.


----------



## SNS1938 (Aug 9, 2013)

Gjash said:


> So you're saying there is no way my st-6800 shifters will work with my 6700 RD? That's the question. I think you're wrong.


I was under the impression that the cable pull from the shifter and rear derailleur pull:movement ratio had changed with 6800/9000. I have just looked on Google, and can't find this for sure, but did find this:

''The lever stroke is shorter than before, and lighter too, meaning less shifting effort, and like Dura Ace 9000 the new drivetrain evens out the force required across the cassette, meaning that shifting in the low gears is as easy as it is at the bottom of the cassette; vivid indexing, Shimano call that.''

You can't normally have a smaller movement and less force whilst moving the same amount of cable.

If I had the parts here, I would have a go to prove this to myself, however I don't have the parts. From the information (or really a lack of information) I can see on the net, I would NOT spend any money ordering parts to try this … there looks to be a pretty good chance that it won't work (maybe it'll sort of work by chance, but it doesn't sound like it was designed to work together properly)


----------



## shoemakerpom2010 (Apr 25, 2011)

I am going to keep on this thread as this proves to be very interesting since the new 6800 levers are so nice and about the same price as the 6700.


----------



## DrSmile (Jul 22, 2006)

mpcbike said:


> Derailleur dictates how far it moves with a given amount of cable pull!!!!!!!!!!!!!


Although I generally agree, technically it's the derailleur attachment point as well as the derailleur design that determines the movement. If someone designed a rear derailleur with a sliding cable fixing bolt, it could be made to work with a lot of combinations (Campy doesn't pull linearly so that might still present issues). People commonly change the cable path on derailleurs to adjust the derailleur movement.


----------



## headloss (Mar 3, 2013)

DrSmile said:


> Although I generally agree, technically it's the derailleur attachment point as well as the derailleur design that determines the movement. If someone designed a rear derailleur with a sliding cable fixing bolt, it could be made to work with a lot of combinations (Campy doesn't pull linearly so that might still present issues).


I don't know. Supposedly, only SRAM pulls linearly, but I'm not sure that anyone has even tested that.

If anyone finds a page that explains RD geometry and how it translates variable cable pull into linear movement across the cog, it would be appreciated. I've been looking but unable to find an explanation at the engineering level. Hopefully a lightbulb goes on soon.


----------



## DrSmile (Jul 22, 2006)

headloss said:


> I don't know. Supposedly, only SRAM pulls linearly, but I'm not sure that anyone has even tested that.
> 
> If anyone finds a page that explains RD geometry and how it translates variable cable pull into linear movement across the cog, it would be appreciated. I've been looking but unable to find an explanation at the engineering level. Hopefully a lightbulb goes on soon.


When I tried to figure this out the thing that made sense to me was that the rear derailleur has TWO points that interact with the cable. The cable housing stop and the fixing bolt. These two points do not lie in the same plane as you shift across the cassette. The pull is affected by the 2 dimensional relationship of these points as the derailleur moves across the cassette. The cable pull would need to change with the difference of the hypotenuse change of the two triangles created for each position. Depending on where the points are to begin with, the pull would either have to decrease or increase in order to keep the lateral movement the same.


----------



## Z'mer (Oct 28, 2013)

It should be easy to measure cable movement versus shift index position. Undo the cable at the rear derailleur, and mark a reference point on it with tape or marker. Then while pulling on it to provide tension, have a helper shift through the gears, while measuring cable length from cable housing to reference point. Put it in a spreadsheet and graph it, you'll see what the relationship is. 
You could also take the front shifter apart and look at the actual step sizes, but that's more work.


----------



## DrSmile (Jul 22, 2006)

Maybe I misunderstood the question... I thought it was accepted that Campy has variable pull. I have tested it myself, it is true:










The question was how that variable pull applies to pull across the cassette.


----------



## Gjash (Jan 17, 2013)

The ratio between Shimano 11 speed and 10 speed has not changed. If it did I wouldn't be able to run 10 speed cassettes with my 11 speed shifters as I'm currently doing.


----------



## headloss (Mar 3, 2013)

Z'mer said:


> It should be easy to measure cable movement versus shift index position. Undo the cable at the rear derailleur, and mark a reference point on it with tape or marker. Then while pulling on it to provide tension, have a helper shift through the gears, while measuring cable length from cable housing to reference point. Put it in a spreadsheet and graph it, you'll see what the relationship is.
> You could also take the front shifter apart and look at the actual step sizes, but that's more work.


Yeah, the problem is that I don't have a SRAM shifter laying around to measure. I've taken individual cable pull measurements for Shimano 9, Shimano 10 (dynasys), and Campy 11. It is an easy enough measurement to take, although it takes a few tries to come up with a system and get consistent numbers (within a margin of error). Likewise, I don't have a Shimano 10 (non dynasys) and Shimano 11 speed laying around to measure. Perhaps I should start borrowing bikes from friends in order to peg these numbers down across the board. I've seen average cable pull for everything, but the individual increments is another story. 

The best online repository, to my knowledge, is Bicycles/Maintenance and Repair/Gear-changing Dimensions - Wikibooks, open books for an open world


----------



## SNS1938 (Aug 9, 2013)

Gjash said:


> The ratio between Shimano 11 speed and 10 speed has not changed. If it did I wouldn't be able to run 10 speed cassettes with my 11 speed shifters as I'm currently doing.


I disagree with your statement. I believe you have 11 speed shifters and rear derailleur. *So all your setup confirms, is that the cassette spacing on 10 speed and 11 speed is unchanged. It does not confirm shifter cable pull or derailleur leverage ratio.
*
It may be that the cable pull at the shifter and leverage ratio at the derailleur have remained the same, however it could also be that the cable pull has halved and the leverage ratio has doubled to compensate, thus still delivering the same derailleur movement across the cassette cogs.

The OP wants to run 11 speed shifters with 10 speed rear derailleur. I cannot readily find any facts about 6800/9000 shifter pull compared to 6700/7900. Without it being stated anywhere, the OP really needs someone to fit a 10 speed RD to 11 speed shifters and have a go.

With the new 10 speed mtb shimano, they have changed ratios from 9/10 speed road, and perhaps have continued this new ratio onto 11 speed road. I cannot see any clear information on this.

It would be good if someone could confirm what's compatible and what's not. It may well be that it all works together fine.


----------



## mpcbike (May 12, 2009)

Ok, pretty sure I've said this a few times already!

YOU CANNOT MIX 6800/9000 LEVERS WITH 10 SPEED REAR DERAILLEURS OR 6800/9000 REAR DERAILLEURS WITH 10 SPEED SHIFTERS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

They have different ratios and the indexing will NOT line up!

I have now actually installed & attempted this both ways, NEITHER WORKS!!!!


----------



## Z'mer (Oct 28, 2013)

headloss said:


> The best online repository, to my knowledge, is Bicycles/Maintenance and Repair/Gear-changing Dimensions - Wikibooks, open books for an open world


This is a really great site, thanks for posting. From the material they present, its pretty clear that the relationship between shifter and derailleur movement is linear at both ends. This means it's defined by a first order equation, y = m*x, where m is the ratio used. They give index steps sizes as a constant, not a variable. 
This would apply to all manufacturers listed there. This info correlates to Sheldon Brown site info, which basically say, for instance, Shimano road derailleurs have used the same ratio (horizontal movement to cable movement) of 1.7 to 1 for all series of index shifters (except for old Dura Ace). 

So for Shimano 10 speed, a cable pull of 2.3 mm x 1.7 ratio ~ 3.95mm, the sprocket pitch. The numbers don't work out exact, as I suspect there have been decimals rounded and not shown for either 1.7 or 2.3 above. 

They don't show cable pull for Shimano 11 speed, but do show 11 speed pitch - 3.74 mm. If Shimano used the same 1.7 ratio on the derailleur, the cable pull per shift would be 3.74 / 1.7 = 2.2 mm. This would be easy enough for anyone with a Shimano 11 speed system to measure. 

Provided they did not use the 1.7 ratio, if you tell us what you measure, it will provide the new 6800 / 9000 ratio. 
One thing is clear, though. The pitch on 10 and 11 speed is different, as they were able to add one more speed by reducing the spacer width, and making the cassette stack only 1.8 mm wider. If they used the same pitch, the stack would be 3.95 mm wider for 11 speed. 
Good news is the cog width is the same, so 11 speed cogs won't wear out faster than 10 speed. Bad news is the pitch is different, so (in theory) you can't use 10 speed cassettes on an all 11 speed system. I say in theory, as it's so close you can likely adjust the RD cable position at the mounting bolt (move toward the bolt center) to slightly increase the travel per shift.


----------



## shoemakerpom2010 (Apr 25, 2011)

Now you need to post this in all other forums you know of since the question has come up in multiple bike forums around the net.


----------



## SNS1938 (Aug 9, 2013)

mpcbike said:


> Ok, pretty sure I've said this a few times already!
> 
> YOU CANNOT MIX 6800/9000 LEVERS WITH 10 SPEED REAR DERAILLEURS OR 6800/9000 REAR DERAILLEURS WITH 10 SPEED SHIFTERS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> 
> ...



Brilliant, thanks. Out of curiosity, can you confirm if shifters 6800/9000 have more or less cable pull than the 9/10 speed ones? I.e. when you had 6800/9000 shifters and a 6700/7900 rear derailleur, did it not shift far enough each shift, or did it shift too far?

thanks


----------



## mpcbike (May 12, 2009)

67 sti to 68 der goes up 2-3, misses 1-2, works for a couple then jumps a few.

68 sti to 67 der doesn't really ever hit indexing correctly & I didn't keep playing to figure out the differences.

I suspect the cable pull to be less in 6700 & the rear der's have radically different angles between housing stop & Cbl clamp.


----------



## Gjash (Jan 17, 2013)

This thread cleared up my ignorance on shifters and derailleurs. Thanks for explanations!


----------



## headloss (Mar 3, 2013)

Z'mer said:


> This is a really great site, thanks for posting. From the material they present, its pretty clear that the relationship between shifter and derailleur movement is linear at both ends. This means it's defined by a first order equation, y = m*x, where m is the ratio used. They give index steps sizes as a constant, not a variable...


You need to know the average cable pull for 11 speed, to determine if the ratio is the same. There are three variables: the pitch, the cable pull, and the ratio between them as actuated by the RD. We only know the pitch for certain, we don't know the cable pull until someone measures it to verify. If the ratio is the same as Shimano 8,9, and 10, then we can plug the numbers. mpcbike seems convinced that it doesn't work, which suggests that the ratio may have changed. I need an 11speed shifter to measure and verify one way or the other.

The cable pull for Shimano and Campagnolo is definitely variable, but the RD translates that non-linear pull into linear movement across the cog. Supposedly, the cable pull as well as the movement of the RD arm are both linear in a SRAM setup, but I haven't tested to see if that is true or a misunderstanding of their "exact actuation" which is nothing more than a reference to their ratio being very close to one. 

What has been puzzling to me, is how the RD translates this movement. I suspect that with Campagnolo and Shimano, they design the cog, pitch, rear-derailler first and then just "key" the ratcheting mechanism in the shifter-control to pull the necessary corresponding cable amounts. I'm confused *if* SRAM works in some different manner to accomplish this.

Like DrSmile suggests, I think there is an interaction of two pivoting points on the derailleur. How they interact isn't a simple first order equation but a calculus of how two such equations interact. Or, maybe it's as simple as using multiple pulleys and I'm just over-thinking it or approaching it the wrong way. I'm not sure if those two pivoting points are fixed in space relative to one another.

One thing to also keep in mind, re: that site, it is a wiki. The measurements themselves are only as good as the person taking it and not necessarily consistent. The numbers for cable pull used are the average across the entire cassette, but the ratio would actually be different for each individual shift. The site doesn't record the individual pulls, so it over-simplifies. As I've said above, I've personally measured Shimano 8,9, and 10(Dynasys only) as well as Campy11 for each individual cable pull. You can see the individual numbers in this thread. Also, if you use any of the ratios on that page, always check the math because a few of them are off. Some people divide by the number of speeds instead of the number of pulls (which is one less) when establishing the average amount of cable pull. As you suggested, the numbers are also rounded. A lot of uncertainty remains, but it is a fun exercise of component design comparison.


----------



## DrSmile (Jul 22, 2006)

Thanks for those cable pull numbers headloss. I knew you had posted them before somewhere! Very rep worthy!

Again I could be wrong on this but I believe the ratios are indeed indicative of triangular hypotenuse relationships between the two points. There is no third order because the derailleur is fixed in the front to back plane. Based on this the pulls can approach a minimal value and increase or decrease from that minimum, but the direction can only reverse once. The minimum would occur where the cable pulls linearly straight back (the triangle collapses into a line). The numbers you have sort of follow that pattern with a few small exceptions, is it possible those are due to the margin of error?


----------



## headloss (Mar 3, 2013)

DrSmile said:


> Is it possible those are due to the margin of error?


Not likely due to any user-error. If there is such a thing, I'm a professional gauge reader and quite good at seeing imaginary lines, within reason. The numbers that I posted are the clean version of my notes, while most of the values were dead on a line on my scale, a couple were a little more fuzzy ( +/- 0.1mm... 0.2mm at the absolute most. I'll see if I can find my original notes). I imagine that I could do a little better with a high-end digital caliper and some sort of off-bike mounting device, but not likely.

I can't speak for other possible issues. The Athena11 was a brand new shifter and cable, as was the SLX-10. My 9speed DA bar-ends as well as the measured 8speed Deore both came from bikes due for new cables. Friction in the housing definitely could have skewed my results to some extent (although, I could consistently get the same measurements, a couple of shifts would have a full 1.0 mm if not 2.0mm outlier. If I could get the same result ten times out of eleven or twelve shifts, that is what I recorded). 

The results were much more accurate going from loose to tight; the cable stuck much more when I let off tension on the shifter. What worked best for me, after several attempts was to tape a good scale to my chain-stay. I folded a piece of scotch tape over the cable. I could slide the tape enough to zero my measurement but the tape didn't slide around at all without an intentional effort. It's best to have the scale fixed to the chain-stay and write down the numbers as you go (a compounded measurement of the total distance from zero) and then just determine the difference between pulls afterwords. If you try to measure each individual shift without a fixed scale, the results are incredibly inconsistent... so much so, that I wouldn't trust most numbers out there unless I knew the methodology used to get them. 

That said, I'm going to see if any of my friends have a Shimano 11speed that I can borrow for an hour. Maybe I can talk the LBS into entertaining me regarding my unique hobby.


----------



## DrSmile (Jul 22, 2006)

I went back and looked at the cable movement some more, and there are two things that complicate my theory: 1) The cable wraps around the fixing bolt and washer and 2) The cable bows more as the derailleur moves outward. This complicates the movement enough that I'd bet the pulls are probably heuristically estimated and then fine tuned / checked by trial and error before production.


----------



## Z'mer (Oct 28, 2013)

Here's another web article with relevant information on the same topic. It fills in the gaps on why the first and last gears are not indexed, as they rely on the derailleur stops. This can explain why, if you measure cable travel from the shifter itself, the travel from the first and to the last position may not be valid data. 

..."That's not a problem because the first click of the shifter always pulls some extra cable so as to take up any slack, with indexing of the top sprocket provided instead by the mech's high-gear stop screw. The low-gear stop does a similar job at the other end of the cassette, so that only the intermediate sprockets are actually indexed by the shifter."

Shimergo | CTC


----------



## SNS1938 (Aug 9, 2013)

mpcbike said:


> 67 sti to 68 der goes up 2-3, misses 1-2, works for a couple then jumps a few...


Sounds like 6700 STI pulls more cable, as you're saying the first shifter index/pull, jumps past a few gears rather than one?


----------



## headloss (Mar 3, 2013)

Z'mer said:


> Here's another web article with relevant information on the same topic. It fills in the gaps on why the first and last gears are not indexed, as they rely on the derailleur stops. This can explain why, if you measure cable travel from the shifter itself, the travel from the first and to the last position may not be valid data.
> 
> ..."That's not a problem because the first click of the shifter always pulls some extra cable so as to take up any slack, with indexing of the top sprocket provided instead by the mech's high-gear stop screw. The low-gear stop does a similar job at the other end of the cassette, so that only the intermediate sprockets are actually indexed by the shifter."
> 
> Shimergo | CTC


The gears aren't indexed, nor is the rear derailleur... those are the same whether you use an indexed setting or a friction shifting set-up. The indexing is in the shifter itself, the indexing is built into the ratcheting mechanism. How the ratcheting mechanism is keyed determines cable pull.

The first and last gears ARE indexed. They have to be, in order to have clean shifting. Think about it, you have to be able to pull enough able to engage the last pawl. If you don't, you will have an unsuccessful shift and it will drop back to the 2nd to last. You also need to be able to shift in two directions, if you drop too much cable or pull to much cable, it will skip a gear or align poorly. 

The indexing isn't particular to the sprocket, it is particular to the gap between each sprocket (which is a combination of thickness and pitch). If you have ten gears, you have nine shifts... no mystery. 

The only place that cable-stop comes into play is in how you make a nine-speed cassette work with an eleven-speed shifter (or any other combination). The limit screw essentially blocks out the extra gears. This can be done on either end of the pull, but I put it on the low gear (big sprocket) end so that it would be impossible to use the last two pawls. To go the other way would allow the shifter to go two shifts too loose resulting in a lot of unnecessary cable slack (although, this is still doable for the sake of aligning the indexed shifts differently... it's personal preference). 

In a designed group, there really shouldn't be any extra slack in the cable to pull or else you need to adjust the cable. If someone is running a lot of excess cable that needs to be pulled before the first shift than I suspect that the spring in the derailleur doesn't create enough tension. The exception being when you shift the lever but the RD hasn't realigned itself yet. If you take your measurements carefully, there is very little slack, so to speak; you have to account for it and correct for it. I'm not sure of the methodology of the person posting in the link you shared, but I disagree with the conclusion you are reaching while reading it. I think you are misunderstanding the comment. He's saying that the indexed shift pulls a marginal amount of extra cable (over-shift) to ensure engagement with the cog, that's not just the first shift but every shift. The high-gear stop screw just prevents it from shifting into the spokes but this does in turn change the effective indexing at the extreme end by cutting it short (as it isn't working according to design)... this just allows you to be creative in how you match a shifter and cassette from two groups that don't match up. It's not some universal truth, just a handy tool that may or may not help depending on the combination.

To get back on the original topic a bit... every designed group allows for some margin, so even if something is technically incompatible, it may still work. It depends on design tolerances (and in the case of a mismatch, luck to some extent). It's possible that between Shimano 10 and 11, the overall pull ratio of the RD remains the same but some of the individual shifts don't match as well. The margin of error comes into place with variations in chain line. What works for one person may not work for another, depending on chain line which varies for many reasons. If the Shimano 11 RD is designed with the same ratio as 8,9, and 10 then no one should be having a problem. I don't know without taking some measurements. It's always best to match components within a group due to these possible unknowns.


----------

