Shimano Di* do and do not.

[Mr Haematocrit]

I have a new Ultegra Di2 with a 25T cassette (brand new bike) and would like to change it to a 28T. By the manual it states that two extra links would be needed in the chain. Would any resetting of the gears be needed if I just replaced the chain and cassette

No you do not have to reset the gears, its also not actually required to swap the chain. I swap backwards and forwards between a 25T and 28T without swapping the chain and it shifts fine

 

[Mr Haematocrit]

BIt OT I heard at the weekend that the Campagnolo system is still campable of limited mechanical shifting when the battery is flat; I think if I had the money for electronic shifters I would lean towards such a system.

It does indeed have limited mechanical shifting. I had Camp EPS it on one of my old bikes, it is without doubt the smoothest, fastest electronic shifting imho but the system is a complete nightmare to troubleshoot and modify.
Mine developed ghost shifting (shifting with no user input at all) and the entire setup was exchanged, to this date I have no idea what was wrong with it.

 

[Archie_tect]

Sorry to come to this so late, but I'm curious to hear, from people who've changed to using Di2 or Si2. Is the benefit of the electronic shift such a user-friendly improvement that you wouldn't go back to traditional gear changing again?

 

[Mr Haematocrit]

Sorry to come to this so late, but I'm curious to hear, from people who've changed to using Di2 or Si2. Is the benefit of the electronic shift such a user-friendly improvement that you wouldn't go back to traditional gear changing again?

I consider myself to be a major Di2 fanboy, I have the diagnostic tools for all versions and a number of bikes with it, including a MTB... Its an outstanding system imho
Im more of a fan though of the early Dura-Ace Di2 as you could cut and splice it as you wished to introduce new features, the latest versions are more controlled and modular, they require diagnostics tools and new methods to tweak. The reality is that modifying them is not so easy.

When selecting a group set for my new road bike I selected SRAM Red 22,
when selecting a groupset for my new MTB I selected SRAM XX1

So although I am a massive fan of Di2, you have to be honest, it has some good points and some bad points as do all group sets.
The reality for me is that at this time SRAM simply offers more value for money, better performance and weight, not to mention its simply a more interesting groupset than Di2 at this time

 

[Sterba]

Could you just use the satellite shifters, without the brake integrated drop bar levers, if you wanted es on a flat bar bike?

 

[Mr Haematocrit]

Could you just use the satellite shifters, without the brake integrated drop bar levers, if you wanted es on a flat bar bike?

Yes, that's not an issue in fact that's what I run on my mtb. It is also widely used by companies such as kedge with their Di2 MTB conversion.

http://www.ki2bike.com

 

[Graham]

Hello Di2 experts! I have just bought a Scott foil with 10 speed Di2 and a 53/39 crankset (no wheels). I'm doing the Cheshire Cat in March and want to fit a 12-30 Ultegra rear cassette to help me get up Mow Cop. Will it work? From what I've read, there seems to be a generally agreed limit of 28 teeth despite Shimano saying 27. Or could I do it but shifting might be a bit rougher? Presumably, if it works, it going to use the full range of movement in the cage so chain length will need to be pretty accurate.

 

[Mr Haematocrit]

There are people running 12-30 with Di2 these days. I personally don't like it and feel it impacts Di2 shift quality in a negative manner.

 

[Peteaud]

There are people running 12-30 with Di2 these days. I personally don't like it and feel it impacts Di2 shift quality in a negative manner.

Indeed there are

Agreed it does not shift as well as the 11-25 but still shifts really slick.

 

[Graham]

Thanks very much both, thought that might be the case. Hopefully I won't need the 30 too often (although this is my first adult (39x53) chainset) so the shifting will be ok between the other sprockets. Seems I might have to turn the b screw round to make sure the upper jockey misses the 30T though (peteaud, did you have to do this?) Hopefully I will get a bit stronger so that I can run 12/27 or similar.Thanks, graham

 

[Graham]

Oh, and I found this about running a 30 if it's of any interest:

http://velonews.competitor.com/2011...tibility-water-bottle-code-ti-seatpost_199011

 

[Peteaud]

Thanks very much both, thought that might be the case. Hopefully I won't need the 30 too often (although this is my first adult (39x53) chainset) so the shifting will be ok between the other sprockets. Seems I might have to turn the b screw round to make sure the upper jockey misses the 30T though (peteaud, did you have to do this?) Hopefully I will get a bit stronger so that I can run 12/27 or similar.Thanks, graham

B screw had about 1/2 turn from the 28 that was fitted. Shifting is as good. Chain length is critical imho and i used an Ultegra cassette and new Ultegra chain. My LBS had the bike in for a service and checked out the rear mech and shifting and all was fine. I am not the only one in these parts parts running the 30T as we have some silly hills round here.

WORD OF WARNING.

The most critical thing is the length of the hanger!!!!!, if it is short it wont work and you may wrech the rear mech.

 

[Mr Haematocrit]

The ramps on the teeth of the casettle which are very specific on the Ultegra and DuraAce Di2 casettes which help with shifting slsickness along with the chain. Swap any of these and you degrade shlifting quality. You can of course mix sections of the casette so its only non-dura/ultegra for specific parts.
You can also buy a billit titanium copy of the dura-ace cassette with the correct ramps in any ratio's you want and these don't encounter degraded shift quality but cost around £200. Spin unobtainium cassettes are pretty good

The shift quality degrading is more noticable on Dura-Ace Di2 as the servos in the mechs are higher specification than Ultegra and faster. If you have upgraded the servos further or undertaken servo mods you are more suspectable to shift performance issues.

I also know people who run bigger than 30 on Di2 MTB conversions.

 

[Peteaud]

How much difference is there between the Ultegra and Dura Ace Cassettes?

 

[Mr Haematocrit]

How much difference is there between the Ultegra and Dura Ace Cassettes?

The difference by large is weight, the ramps are the same. The Dura-Ace casette is part titanium and the Ultegra is not
You do find that the Dura-Ace seems to wear a little better so its performance is more consistent over a longer period of time.