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Retromoding a bike with disc brake at the front. The lever is a Deore 6100 with I-spec EV attachment.

The bike will get a crankset with a double Chainring and a 10 or 11 speed setup for the rear. I will also install a 2 speed front mech.

I searched for front / left shifters with I-spec EV and only the latest came out (M7100, M8100, M9100). This is all 12 speed stuff. Of course mine will be 10 or 11 but would that shifter made for the 12s series work? After all I'm installing 2 speed front mech and this is a 2 speed shifter. I guess pull ratio should be the same?

Many thanks

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  • 9100 is the model number for 11s Dura Ace. And specifically, FD-9100 would be the mechanical FD and 9150 would be the Di2 FD. For 9200 and 8100, only Di2 components exist. 7100 has a mech and a Di2 version, though.
    – Weiwen Ng
    Dec 27, 2023 at 14:13
  • @WeiwenNg 9100 is also the number for XTR. R9100 is Dura-Ace, M9100 is XTR.
    – Rеnаud
    Dec 27, 2023 at 14:14
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    Good point, I forgot about XTR.
    – Weiwen Ng
    Dec 27, 2023 at 14:15

2 Answers 2

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There's another shifter that is compatible I-spec EV that you didn't mention: the SL-M5100, meant to be used in 2x10 and 2x11 transmissions. For what it's worth, my fun bike is using a M5100 shifter with an Acera front derailleur (9-speed officially, and the combination is unsupported by Shimano) on a 2x10 transmission, it works better than when it was a full Acera.

That being said, it's also possible that the 9100 would work, but given Shimano doesn't publish any info that would allow to verify the claim, the only way to know is through experimentation (or measurements). As far as I understood, pull ratios for front derailleurs are indeed the same, for road and MTB alike. Double chainring setups are more tolerant to mismatches that triple, as ultimately, there can be only 2 positions: under tension and released, no need to make sure that the intermediate position is perfectly tuned. So I cannot say much more that "probably compatible", but the M5100 shifter is the option I would choose with the constraints you give (it's a "1 lever/2 ways" shifter, it has the most important feature for a double chainring shifter but it will be a bit less "refined" than the 9100 - finish and materials).

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  • Great suggestion. M5100 is officially compatible with 2x10 and 2x11. What do you mean it's "1 lever 2 ways so is less refined" ? I'm reading 5100 is a 2 way release so should be able to downshift by pushing with thumb like a Slx, Xt, Xtr?
    – tweedi
    Dec 27, 2023 at 12:27
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    @tweedi yes, it's possible downshift by pushing or "pulling". Less refined in the sense that materials and finish are good instead of being excellent like on a XT/XTR. It also lacks "instant release", but again not an issue. By "1 lever", I mean you don't have a lever for the thumb and one one trigger for the index (that works both ways), you just have one lever, forward position you are on the big chainring, backward position you are on the small chainring. That's for me the best kind of lever for a double chainring.
    – Rеnаud
    Dec 27, 2023 at 14:09
  • I've not specifically mixed 12 speed front drive components with 11 or 10 speed parts but have always had excellent shifting mixing 9 &10 and 10 & 11 speed front drive components (Shimano exclusively). This includes differing shifters with derailleurs and crankset's with front derailleurs of different generations (+/- 1 generation between components).
    – Jeff
    Jan 17 at 22:51
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One possible solution--or at least an option to give you more selection--stems from the similarity of I-spec 2 to I Spec EV in terms of the nut and bolt used as well as the design of the shifter.

I spec2 works by mounting a piece onto the shifter that then fits underneath the clamp band of an I spec 2 brake. If one takes an I spec2 shifter, removes the piece that fits under the clamp band of the I spec2 brake and keeps the bolt and the block/nut that held that piece onto the shifter, what you have at the shifter is the same anatomy as an I spec EV shifter-- the long slotted area that the square box-like nut interfaces with when it's coming from the I spec EV brake. Essentially you can marry an I spec 2 shifter to an I spec EV brake by eliminating the band clamp interface piece of the I spec2 shifter and utilizing the special nut and bolt to fix the EV brake lever to the slot on top of the I spec2 shifter.

There is plenty of adjustability to position the lever where desired. I did this mod on an I spec2 XTR shifter (SL-M9000) to marry it to my XT I spec EV brake lever, (BL-M8100). This was on the right side on a 1x drivetrain but would work equally well on the left. Note that you cannot marry an I spec 2 brake lever to an I spec EV shifter. There's nothing at the I spec 2 brake lever to hold the block-like nut that interfaces with the slot on the shifter.

This mod then will open up all the I spec2 shifter options (most mid to upper tier 11 speed mountain shifters from Shimano) for your upgrade.

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