Spin Doctor Tech Tip – Shimano Dura-Ace Di2 Electronic Shift System

So you’ve won the lottery and your first big purchase is Shimano’s new electronic Dura-Ace Di2 drivetrain.

Before you install it, BE ADVISED that your ego may be put in jeopardy. Yes, the new Di2 components are so slick that your bike, once Di2 adorned, will be smarter than you. Push a button and you have perfect shifts every time. The front derailleur will automatically trim itself to eliminate cross chain rubbing, and the rear derailleur disconnects its motor when you lay the bike down. The system will even tell you when the battery is low or if there’s a malfunction. Plus the battery lasts 1000 KM and will recharge in only 90 minutes.

Like we said, this stuff is SWEET!

Even better, Dura-Ace Di2 meets the “clock on the VCR” standard. If you can program the clock on your VCR, installation of Di2 will be a snap. The components come with good, clear installation and set-up instructions plus Shimano has an even better online tutorial, http://di2certified.shimano.com. That site features both a how-to video and an interactive installation and operation lesson.

But there are a few small subtleties that, if missed, can short circuit Di2’s marvelous performance.

Be aware of these issues:

• Do not touch the cable connector terminal/contacts. The system is great but can malfunction if the contacts are fouled.

RD-7970 rear derailleur

• The RD-7970 rear derailleur will  accommodate cassette cogs as large as 27 teeth, no bigger. Do not be tempted to install the new Dura-Ace 7900 11-28 cassette; it will hang up.

SM-BTR1 battery pack

• Be sure to remove the battery when installing the derailleurs or repositioning them. The motors in the derailleurs are powerful enough to break or badly pinch a finger.

FD-7970 front derailleur

• If you are installing the FD-7970 front derailleur on a braze-on mount, be sure to use the provided small stainless steel patch to protect your frame. The FD-7970 uses a “support bolt” that screws against the frame to orient the cage relative to the crank. The support bolt will damage the frame if you have failed to attach the protector.

TL-EW01 tool

Removing rear derailleur connector

• The wiring harness comes with a plastic tool (TL-EW01) to plug the wiring harness electrical connectors into the brake levers/shifters. It is also to be used to disconnect any of Di2’s electrical connectors. Use the tool! Do not pull connectors apart.

ST-7970 dual control levers

Auxiliary terminals

• The ST-7970 brake levers/shifters have additional terminals for auxiliary shifter buttons. If you are not going to use them, seal them from the weather by installing the provided dummy plugs.

• The new CN-7900 chain is asymmetrical and shifts great when correctly oriented. Install it so that the non-perforated outer plate (engraved with Shimano & Dura-Ace logos) is on the outside.

• When properly assembled the Di2 system is extremely waterproof, but individual components require special care when cleaning:

  • Do not soak components in degreaser. This may damage critical seals.
  • Shimano recommends cleaning components with a rag soaked in mild degreaser. Do not use a spray or brush, as they can damage the seals.
  • The articulated joints & pivots of the Di2 front and rear derailleurs are connected to the internal servo motors. Lubricating these pivots may damage seals and expose the motor to contamination.
  • Maintenance of the pulley can be done in the same way as with a conventional derailleur.
2010 Scattante CFR Pro

2010 Scattante CFR Pro Shimano Dura-Ace Di2 Road Bike

So what was the test rig here in our office to learn all about Dura-Ace Di2? None other than our very own 2010 Scattante CFR Pro Shimano Dura-Ace Di2 Road Bike (seen here in our Technical Support area). Featuring our brand new sub-1000g CFR-A3 Frame, with BB30 crankset, this is definitely a worthy ride upon which to hang a complete Dura-Ace Di2 drivetrain.

25 Responses to Spin Doctor Tech Tip – Shimano Dura-Ace Di2 Electronic Shift System

  1. Derrick says:

    Have had my Di2 for about 6 months now and love it, I am looking to change from 12-25 cassette to 11-27 or 11-28. You noted above that the 11-28 will hang, Shimano’s site lists that the rear derailuer can handle up to 28 cog, have there been a lot problems with the 28’s now that they have been out a while? Any similar trouble with the 11-27’s? I need all the climbing help I can get.

    • Talked to our tech team, and they said that the maximum rear sprocket officially sanctioned by Shimano for the Di2 rear derailleur was 27 teeth (with a total capacity of 32 teeth or less). Now you could probably make it work with 28 teeth, but you will probably have to adjust the B screw and you may not get the absolute finest shifts (and that’s what you want from Di2). Long story short, you can go up to 27 teeth with no problems, even with a compact crankset. Hope this helps.

  2. Hiran says:

    We run it with a 36 on our race bikes so it can be made to work :-)

  3. Angus McCulloch says:

    I have UDi2 but find the rear derailleur does not shift as smoothly from smallest cog to second smallest as it does with the rest of the rear cogs. I have it set up and adjusted as per the workshop manual. I am using a KMC silver 10speed chain and not an Ultegra chain. But the thickness of chain is the same. Could the chain be the issue?
    The shifting takes a bit longer and just sounds bad as it sounds like a chain that will not shift.

  4. Eli says:

    i just got the di2 ultegra, works great my concerns are about daily maintenance for example;
    if it gets rained on and in sth florida it can happen at anytime. just basic cleaning and lubrication of the system; when, how and what is and is not recommended to use if anything?

  5. Dennis Page says:

    Just got a brand new Scott premium with dura ace di2 and rear dérailleur failed on the second day. Battery is fully charge, tried to hold reset for 5 sec and rear dérailleur will shift all the way down and then back up. When I try to shift I get no response from rear. The front works well. I also disconnected the wires and then plug them backin again.
    Will take it back to the bike shop tomorrow but that’s very frustrating.

  6. Matt says:

    I have Dura Ace DI2 7970.I recently changed from a Dura Ace 7900 12-27 cassette to an 11-28 when I switched to compact cranks. While Shimano recommend a 27max the 28 works just fine with a small adjustment of the B screw. There has been no change to shift quality. Hope this helps…

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