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I got a road bike with the Shimano 105 R7000 groupset (including Shimano 105 R7000 52/36 crank, Shimano 105 R7020 hydraulic brakes and the cassette HG700 11-34 11s).

I would like to upgrade it to the Shimano 105 Di2 R7100 spending as less money as possible.

Is it possible to keep my crank and cassette, although the Shimano 105 Di2 R7100 is 12 speed? (Is there any software configuration you set to use other cassettes?)

If not, would the 12 speed cassette fit my DT Swiss P1800 Spline DB32 or do I need a new back wheel?

Thanks!

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  • 1
    It's cheapest to buy the group as a bundle deal.
    – Noise
    Aug 10, 2023 at 6:29
  • 1
    The cassette will fit your wheel.
    – Noise
    Aug 10, 2023 at 6:29

1 Answer 1

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Shimano has a pretty good compatibility chart.

These things are "incompatible" according to the chart

  • 11/12-speed drivetrain, I guess that should be clear, so the rear mech won't deal with a 11-speed cassette and you should run a 12-speed chain which is a tiny bit narrower and optimized for the cassette. Even if would be easy to adjust electronic gearing to narrower 12-speed gaps than a mechanical shifter with physical "clicks", Shimano has no intention to make this compatible and update their firmware, I presume.
  • The 11-speed crank and the 12-speed derailleur: There are no specifics given but there is 1 mm chainline difference. That's something that can probably be worked out, at least on a mechanical groupset, it might be that Di2 adjustment is a bit more delicate or shifts not as crisp as on a full Di2 group but I have no practical experience.
  • According to the chart, the new Di2 ST-R7170 levers are not compatible to your old BR-R7070 calipers, however, the other way around, ST-R7020 (your current brifters) work with new calipers, so I guess that should be OK and just Shimano keeping things simple in diagram, no real limitation. Same brake hoses, same pads, only their homepage claims 10% more pad clearance, I assume this refers to the previous generation of calipers.

So, the minimum you need for an upgrade is

  • STIs (left/right)
  • Cassette (will fit your wheel)
  • Di2 Front/rear derailleur
  • 12-speed chain
  • Di2 battery
  • (possibly a 12-speed R7100 crank if it turns out to be problematic)

If I just put these on my cart at my usual shop, it is worth about 900€ of components but they have a deal on the full set for under 1200€ which gives you calipers, rotors and matching components.

So, it might be worth considering doing a full upgrade and just sell or re-use the leftover R7000 parts.

The only thing I'm not sure about is availability of a 52/36 crank, the chart shows compatibility of the derailleur (max. 52t) and Shimano's Shimano's product page lists it as an option for FC-R7100 but I haven't found a mid-compact option in the 105 range, neither as an individual component nor as part of a full 105 R7100 groupset, only 50/34 in all crank length options from 160-175 mm.

You would have to work around by using a non-Shimano 12-speed crankset or using a 12-speed Ultegra crank (which has a 52/36 option it its current generation) - or accept the lower gearing, I only use 50-11 twice a year on a big descent.

Note: Last section about chainring sizes was written to the best of my knowledge at the time the answer was given, if Shimano decides to widen its range, kindly ignore it.

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    FYI, many pro road teams carried over their 11s cranks this year due to lack of supply, esp. of the power meter 12s cranks. As far as I know, people seemed to report slightly worse shifting, some dropped chains. However, they are putting more stress on their stuff than mortals are.
    – Weiwen Ng
    Aug 11, 2023 at 13:14
  • @WeiwenNg Yeah, there is a question addressing this here which I recently read. Wasn't 11/12-speed, but slight change in chainline means exactly that...You can tweak limits and tension but shifting's never gonna be as good and the offset might lead to chain rub on extremes and/or more frequent chain drops. In the end, there is a reason why Shimano doesn't approve of such combinations. I'd just go for full 12-speed, drivetrains are usually enough of a mess within spec.
    – DoNuT
    Aug 11, 2023 at 14:26

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