Goldrush

First off, this setup gives 26 gear inches for the low, where my current 30 tooth granny with 34 tooth cassette gives a 23 inch low. We do not live in the mountains and still need every bit as low as the 23 inch. If we went on a tour in an area with bigger climbs we would need lower yet.

Secondly what rear derailleur do you use to shift to a 40 tooth cassette. My XTR long cage is rated for 36t max.

chojn1

The 40t cassette is the new upcoming XTR cassette to be used with the new XTR DI2 rear derailleur. A compact 34-50 compact crankset will get you there. If you need even lower gears, then just use the inner and middle rings 30-48 set up as a double. But I understand the preference for the closer spacing between gears.

CJ

twocicle

Nice product update on the Shimano website:

Mountain bikers enter the digital age with XTR Di2

I can see the XTR FD capacity being a problem for us roadies wanting to use it with our much bigger chainrings in either a double or triple setup. The FD cage looks quite short and so probably can't handle a large ring difference (ie: 52t to 30t).

Hopefully some of this new tech will trickle down into the Di2 road groupo.

chojn1

I was playing around with the E-Tube software last week, Shimano has already updated it to handle the new XTR components. Unfortunately, they made a clear distinction between the road and MTB groups. Unless they drastically change the software, I don't think the components will be interchangeable. It may be hacked to work, but forget about software support or sequential shifting for the road group for a while.
CJ

twocicle

This is all guesswork at the moment, but I disagree. You could likely still access the mtn derailleurs and operate those using "manual operation" mode that is available when using dual (left/right) mtn shifters. It may be that the SC-M9050 Display Unit is needed to put them into the correct mode, but otherwise my guess is road shifters should otherwise work with the mtn derailleurs.

chojn1

You are right of course, I do not have the parts to play with.
And I don't doubt you can get the road shifter to operate the XTR derailleurs.
But, the E-tube software as it is written now will not recognize the different components on the same bike.
So you essentially will not be able to use the software to update or program your system if you mix the components. Functions like multishift or sequential shifting will not work.
Of course Shimano could revise the software sometime in the future and maybe before the XTR release.
CJ

Carbonfiberboy 

[QUOTE=Goldrush;16806157]I don't usually have any problem with our XTR. Always works like a charm, as long as I don't screw up the cabling or housing. I had a heck of a time with it for several months (!) until I finally figured out that I'd grabbed a piece of brake housing for that last run into the RD. Going to Alligator housing up front and all Jagwire smooth cables made it better, but it really shifted fine with the stock STI.

twocicle

It's not necessary for the E-Tube software to see all components at once. You specify (checkbox) which components E-Tube should search/find. So, you can select just the road components or the mtn components.

Both the Di2 and mechanical 11spd (M9xxx) mtn derailleurs have the same capacities. Sadly, the FD cage was shortened and in the max triple ring configuration is designed to only handle a 18 tooth spread (22 x 30 x 40) and not the typical 22 tooth spread (30 x 39 x 52) of a road triple.

here's another page with various tidbits...
https://www.pinkbike.com/news/first-l...ur-choice.html

2frmMI

There was a fairly definitive note at velonews about incompatibility between road FD and XTR Di2 rear.
From Velo News:

"The main issue for mixing road Di2 front and XTR Di2 rear systems is the massive 11-40T cassette used by XTR.

The 40T cassette is going to put the chain at an angle that the road FD is not designed for. There is a good chance it will rub on the top of the FD cage.

This incompatibility between the 11-speed road front drivetrain and the XTR Di2 11-speed rear drivetrain will keep this combination from working. Therefore, Shimano Synchronized Shift will also not function when this combination is used.

We don’t have a solution today for road riders as Shimano engineers prioritized Shimano Synchronized Shift for mountain biking, where it provides greater benefits and enhances the ride in riding environments where the terrain is challenging. However, we do feel that this is a function that will benefit many types riders. We will continue to study and should have more to say on this topic in the future.
— Dave Lawrence
Shimano Product Manager"

waynesulak

First the wording "is going to" and "there is a good chance" above makes it clear that they have not tried it and the statement is speculative. Understandably Shimano does not want to say it will work unless they are ready to take responsibility for it working perfectly in all situations.

Second - Why not use a road cassette which would avoid the 40 tooth cog? How many people want a 40 tooth cog and a triple on the road?

I am not saying that it will work. I just think until someone can actually try it then we don't know if it will work out of the box or if there is a work around available. For example in past years any Shimano or Campy representative would say you could not use Campy 10 speed shifters with Shimano 10 speed cassette but there are many who use this combination with a variety of configurations.

It is typical (and easy) for Velonews to just quote industry representatives instead of trying to test some like this themselves.

2frmMI

Yes, I guess I can see a more nuanced reading of this. Anyway, I'm still very interested in the potential of this XTR Di2 for tandems.

LastKraftWagen

If the possible issue is rubbing "the top" of the road FD with the 40T cog, then maybe the issueis front ring selection? Tppical front granny is what, 30T or 28T perhaps, with perhaps a 32T cog? ost likely with the 40T cassette a 30T will rub, but maybe not a 39T (or larger) small ring?

I can't dplicate this on m own bike, and the toleranes are too small to feel, its just speculation and food forrthought. Guess italso dpends on chainstay lngths and angles.

Personally, I drool just a lttle over the idea of a 55/39 front and 40/11 (or maybe even a SRAM 42/10 if I read it ight) cassette.

2frmMI

My interest in the Shimano manager's comments is quite related to what you suggest. I'm limited to double front, since I have right side timing belt. I currently have a compact double (50/34) in order to get down into a reasonable (for us) climbing gear with an 11-36 cluster (largest capacity with K-edge modified Di2 Ultegra RD). I miss having a 52 or larger big ring, and it seemed to me that having the XTR 11-40 cassette would probably allow me to use 55/39, as you suggest. But it sounds like the XTR FD may not handle those big rings, and so I'd need to stick with my road FD. What Shimano says is that road FD will be incompatible with 40 cog: just the combo I might find interesting.
Wayne may be correct about those with a triple, but I'm not one of those, and won't be unless I want to ditch the right side drive - unlikely. Now, if the XTR FD actually ends up working with road-sized chainrings, this could all change. The other big XTR-Di2 draw for me would be the synchronized shifting, which hopefully will come to road sooner or later anyway.

twocicle

^^^ note that use of any 11spd XTR cassette or chainrings will necessitate using the M9000 series asymmetric chain as well. It wouldn't matter which 11spd chain (road or mtn) for the derailleurs, but especially for the 11-40t cassette - if anyone did desire to use that pie plate on the rear.

Also noting from the above Product Manager comments, the only road/mtn Di2 derailleur incompatibility mentioned was due to the 40t cassette and the absence of synchro shift. Otherwise, still a maybe?

waynesulak

It is refreshing to read a right side drive proponent say they miss some gears they would have with a triple. I understand that it is a question of priorities and for you the right side drive is more important. We all have to make trade offs. I would rather have the gears I want and a triple.

waynesulak

I am thinking of of a Di2 road group except for the FD and RD from the XTR group.

LastKraftWagen

[QUOTE=2frmMI;16996136]My interest in the Shimano manager's comments is quite related to what you suggest. I'm limited to double front, since I have right side timing belt. I currently have a compact double (50/34) in order to get down into a reasonable (for us) climbing gear with an 11-36 cluster (largest capacity with K-edge modified Di2 Ultegra RD). I miss having a 52 or larger big ring, and it seemed to me that having the XTR 11-40 cassette would probably allow me to use 55/39, as you suggest. But it sounds like the XTR FD may not handle those big rings, and so I'd need to stick with my road FD. What Shimano says is that road FD will be

Did I read somewhere that there is a SRAM 10T cog? Could that be fitted to a Shimano cluster? Either converting it to an 11spd, or reworking the cassette to add the 10T. Then you would have a 50/10 tall gear which is bigger than the 53/11. Tooth pitch should be the same, but a spacer may be required to match 10spd chainwidth.

If you go with the 11spd option, you will have to swap RDs, but the K-Edge modified cage may swap over...

Or, we can go back to six-speed triples with friction shifters...those I understand.
incompatible with 40 cog: just the combo I might find interesting.

mstyer

SRAM's 10T cog only comes as part of their 10-42T cassette and is too small to fit on a standard freehub body. It needs to be fitted to a hub with an XD driver body.

2frmMI

Does -having- a right side drive make one a -proponent- of right side drive? I don't recall ever having taken a position other than with my checkbook. I would put us squarely in the camp of "gathering data" on this. The data so far are that stoker thinks we climb much better. And at whose peril shall we debate what the stoker thinks?

waynesulak

Well said. My inference was made from your statement that you use it and were unlikely to ditch it. I did not give due consideration to your stokers possible input into the matter.

Bad1

How many people including yourself have the horse power to spin a 55x11 out in a down hill, much less on the flats, I've found mid-compact 52/36 much faster overall for our team versus 53/39 on a dbl. front chain ring set up, the last Fondo we did 117 miles 7k vertical we used a Compact 50/34 and was amazed at how much faster we were overall, more rpm with less effort = more endurance IMO..

Dean V

We usually run a 56x11 top gear. I find it quite useful for helping to drop other riders on fast sections. Don't need much of a downhill to get over 40mph on a tandem.

LastKraftWagen

[QUOTE=Bad1;16997755]How many people including yourself have the horse power to spin a 55x11 out in a down hill, much less on the flats, I've found mid-compact 52/36 much faster overall for our team versus 53/39 on a dbl.
Many teams, including myself, can spin out a 52T or 53T /11... 55T is only about 3.7-5.7% taller. And its not only about spinning out the gears, gear grinders (slow cadence riders) may appreciate the nearly 6% reduction in rpm over a 52T. A 55/11 at 100rpm is only about 63km/h. A decent tailwind in the aero bars even we can reach 39mph. No, we can't hold it, but we can drop the occasional wheel sucker.

front chain ring set up, the last Fondo we did 117 miles 7k vertical we used a Compact 50/34 and was amazed at how much faster we were overall, more rpm with less effort = more endurance IMO..
Comparing "faster" between two rides, or the same ride at different times, is subjective at best. There are just too many variables involved- weather, fitness, terrain (for different routes), how long the lines were for the bathrooms or bottle refill stations. Point being that it is very possible the compact gearing helped, but while higher cadence/lower force is more efficient for many, its not the case for everyone. Some riders are more efficient (have more endurance) at a slower cadence with more force to the pedals (this is actually the topic of my masters thesis). It depends largely on muscle fiber composition.

Team Fab

We are definately in the low rpm department. My stoker has problems getting above 80 rpm with 90 max.

I used to be able to get up 145, but have now adapted the high power low cadence.

Low rpm does not seem to hinder our endurance as we have still done up to 250 km days.

And when we ride with singles the only way for us to drop them is on the downhills with a high top speed, so we love our 55 big ring.





[QUOTE=LastKraftWagen;16998321]

Team Fab

Also, look at Chris Horners climbing while standing, seems to work quite well for him.