vyborne

As mentioned in my last thread, I am doing my first Di2 build: a triathlon bike with Ultegra 8050 front and rear derailleurs, 8060 TT levers and Dura Ace 9160 extension shifters. I have never built a bike with Di2, or even used one, so I am learning on the job.

One thing I learned in the process of getting my defective rear derailleur replaced under warranty (dead out of the box) was that there is a minimum size for the largest cog in the cassette. I know this isn’t news to most people here, but I had only ever heard about maximum cog size limits before.

My problem is that I had planned to use a 52/36 ultegra 8000 crank with a 11-23 ultegra 6800 11 speed cassette and Shimano says a 25 tooth cog is the smallest that can be used with my 8050 short cage derailleur. Has anyone used, or know if you can use, a 23 tooth cassette with current Di2?

My next question is about full synchro shifting. Since I have single button shifters, this is the mode I will almost certainly use. When you customize the point at which the front derailleur shifts, are there limits/best practices as to how many cogs the rear derailleur can shift across? Also, assuming I can use the 11-23 cassette, how do I set this up given my cassette isn’t listed as an option in the e-tube project software?

Thanks for helping me move into the 21st century!

Steve B.

For whatever reason, Shimano stopped manufacturing an 11 spd. 11-23 cassette. It was a favorite of mine as it had near one-tooth jumps which is useful on flat terrain where I ride. I only noticed this when I was setting up my Di2 system the first time (4 years ago) and became aware that 11-23 was not an option when "telling" E-Tube that's this is the cassette you are using. E-Tube only allows you to tell it a cassette range currently manufactured by Shimano.

However, the system has no way to actually count cassette cogs and you can still use an 11-23 and just tell it you have a 12-25 or whatever. One downside is you have to think thru the shift map if using Synchro - I.E. figure out where you want the shifts to occur if it were using an 11-23 and cheat the system by mapping that. The other downside is if using a GPS head unit that displays the gears. It'll be incorrect as to the gear you are in.

Note that if you have no need for Synchro Shift, turn it off and set the Gear Position in the E-Tube software to off. Then "tell" E-Tube that you have a 53/39 crank and a 12-25 cassette (or some combo) and you will defeat the limitation of not being able to use the 2 smallest cogs while in the small ring, which is something Shimano locks out with particular crank/cassette combo's.

August West

On the current generation Garmin 530/830/1030 you can choose to have the head unit automatically get the chainrings/cogs from Di2 or choose to manually enter them in the head unit. If you choose manual you can set it cog by cog to whatever you are running.

vyborne

Steve B. – so it sounds like I should have no problems from an e-tube perspective. From your comments, I’m guessing you have used the 11-23 cassette. Did you experience any problems? Is there anything I should know when installing/setting up the derailleur and cassette on the bike? One issue I might have (and the reason I became aware of the limitations) is that Shimano only has gs derailleurs in stock and my defective one was ss. It will be at least another month before they have ss in stock. Do you know if both derailleurs can handle 11-23 or only ss?

August West – thanks for the info about the new garmin units. Unfortunately, I have a 520, so I’m out of luck.

cxwrench

The 11-23 will work fine. I'd go with the SS derailleur as the GS moves at a steeper angle to work w/ bigger cogs so the upper pulley will be pretty far away from your (smaller) larger cogs.

TerryDi2C

I have successfully used 11-23 with a (6870) GS derailleur. It is outside the Shimano recommended spec, but it'll work.
(Shimano would probably argue it doesn't work as well as it should and it doesn't provide the experience they would like, but it does work )

Quote:

Also, assuming I can use the 11-23 cassette, how do I set this up given my cassette isn’t listed as an option in the e-tube project software?

The selected cassette in E-Tube Project changes two things

• Whether or not Gear Position Control is enabled or can be switched off (also depends on chain rings)
• The displayed values for the gear ratios and number of teeth in the Synchro Shift setup screen

It doesn't actually affect how the synchro shift works, but the listed number of teeth on the synchro page (and gear ratios) will be wrong. Instead you just select the closest match in E-Tube (11-25 for example) and then use the cassette sprocket/cog number when settings it up.
If you set up synchro shifts to happen when the cassette reaches the 3rd sprocket, that's what will happen. If you set it up to shift on the 10th, then that'll happen .
(ignore the number of teeth on that screen and look at the position or sprocket 'index' instead)

Steve B.

I will have to go back to this. There is a way to set the cassette on the Garmins, last time it tried it it would revert back upon BT connection to what was set by E-Tube in system. Maybe they fixed this,