Shimano Di* do and do not.

[ianwoodi]

My chain on my di2 keeps coming off it happens when i am in largest chainset and in largest gear on cassett it will come off if i pedal backwards and some times drops when i am changing from big to small chain set is it the way i am riding it or is there a fault

 

[Mr Haematocrit]

Ultegrea or Dura-Ace?
Does it have a full ultegra/dura-ace chainset?

 

[ianwoodi]

hi it has sram 50/34 chainset with a 25-12 cassett

 

[Mr Haematocrit]

Di2 imho never works as slick with other chainring/casettes as it does shimano chainring/casette.
Did you just fit and forget, or set the shifting up following the process in the Di2 manual?

 

[GrasB]

Di2 imho never works as slick with other chainring/casettes as it does shimano chainring/casette.
Did you just fit and forget, or set the shifting up following the process in the Di2 manual?

Item of note Shimano & SRAM (along with most of the other Shimano compatible component manufactures) use different chain lines, not massively different, about a 1/2 a chanring's width but different enough that it gets noticed by mech when swapping between components.

 

[ianwoodi]

Its all been set up with manual all gearing works fine fast and smooth its just the chain drops every so often it could be my riding went up a hill this morning around 10% hit the hill in large front ring in big gear on cassett and changed it down to the smaller front ring and it fell off am i expecting to much

 

[Mr Haematocrit]

I do not expect to see chain drops on Di2 and the typical times I have seen them the setups have not been setup as instructed in the manual, or have non shimano cassettes and chain rings, which is why that was one of the first things I asked .
As a bit of a weight weenie, I have tried a number of billet cassettes and found they impacted shifting negatively im now running a shimano cassette again.
On Shimano cassettes I can shift down and up while on power, it seems that people with sram cassettes and other brands need to back off and not put a load on the pedals to shift in an effective manner at times. Although you can 'touch' the shifter on Di2 with a non shimano cassette you get better success pressing the shifter and holding it for a second or two... fast shifts cause chain throws.

Ultimately I would advise moving to a full Shimano setup

 

[GrasB]

I've got a 53t 105 chainring & 53t SRAM chainring on my desk right now. The biggest thing you notice is that the SRAM chainrings are flat where as the 105 is noticeably dished. This difference is likely to have a significant effect on the way the chain moves between chainrings. On the SRAM rings the chain effectively free-falls from the top chainring to the bottom one. On the 105 it will ride over the dishing & be delivered to the bottom chainring. The detailing on the 105 & Rival front mechs is also different with the 105 having far less metal towards the front of the mech on the inside, suggesting it needs to have less control of the chain.

The reason I have the chainrings & mechs on my desk? Cause I wanted to know why the hell I can't get the 105 mech to work well without dumping the chain on downward chainring shifts on a regular basis. It's also interesting that I've tended to find that SRAM front mechs work much better with 3rd party chainrings, which are almost exclusively flat rings rather than dished.

 

[Mr Haematocrit]

Great info GrasB thanks for sharing and helps me start to understand why different cassettes can effect the slickness of Di2 a great deal

 

[GrasB]

I've not looked into cassettes my self, as I run SRAM rear mechs which seem to just work with anything you throw at them as long as the indexing matches up. Also if you can put up with a 50grm weight penalty & use inline cable adjusters their MTB rear mechs are much nicer for cable routing

Shimano front mechs however tend to have a larger chainring range capacity. They just dump the chains more often using aftermarket chainrings. So you can do 34/58 but you'll drop the chain every 10 chainring swaps, where as with SRAM you get reliable shifting but have do 34/54.

 

[ianwoodi]

thanks great info

 

[grantxdavis]

Is there a link for the owners manual for DA 7970?

 

[Mr Haematocrit]

Is there a link for the owners manual for DA 7970?

All manuals are available from the following URL :-
http://techdocs.shimano.com/techdocs/index.jsp

 

[Andrew_P]

Shimano sell an after market seatpost battery for Di211 but im not aware that Specialized are using that, all the bikes I have seen personally have had the external battery on the bottle cage mount, but the most recent pictures on the specialized web page noticably show this missing. So perhaps they have started doing this, or moved the battery elsewhere.
The bike looks better for it though imho.

I have been talking to a Specialized Elite retailer in the Southwest, I have been quoted £4250 for Ultegra Di2 + S-Works SL4 Roubaix Frame + S-works Stem & Bars. Will use my own Saddle and Wheels if I press the buy button. I would reckon I could get that below 4k if didn't use the 0% finance.

I asked about the battery mount and the reply was Specialized mount as per this picture, still looks a bit fugly. http://cdn.media.cyclingnews.com/products/bikes/road/1301910323759-cptcny2di34s_600.jpg

How much is it going to be a pain getting the Ultegra in to the Seatpost? Could I mix and match Groupset between DA & Ultegra to ease that pain?

 

[Mr Haematocrit]

The Ultegra Di2 is built using the etube technology of the new 11 speed Dura-Ace Di2 as such some people are saying the the official 'optional' Shimano seat post battery also works with Ultegra however this is not something I can confirm myself and will not do so until I have seen it in the flesh with my own eyes.
You can get a few people making after-market battery's for Ulegra however the process for building them is more complex than that required for 10 speed Dura-Ace Di2 which is just a straight battery replacement and loom as such its reflected in the price. Alternatively you could always build a battery pack yourself if handy with a soldering iron.
Frame batterys are fugly imho