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I am aware that with the introduction of the Tiagra 4700 groupset Shimano now uses the 11-speed road cable pull ratio also for their 10-speed road systems. Therefore a Tiagra 4700 right shifter is only compatible with Tiagra 4700 rear derailleurs and 11-speed road rear derailleurs.

Because I would like to run smaller chainrings in the front for my 2x10 setup I need to use a MTB front derailleur. Is this possible with a Tiagra 4700 left shifter or did the cable pull ratio change there as well? If not: Can I use a Sora ST-R3000 left shifter from their 9-speed road groupset instead? What are my options? Which MTB front derailleur would I have to use with which road STI shifter?

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    I wonder if you really need an MTB derailleur. Presumably you have a braze on version and can't get the derailleur low enough? What size rings do you want to use? – Argenti Apparatus Apr 13 at 18:27
  • @ArgentiApparatus for the largest chainring I would like to use less than 46 teeth which is the minimum required for road derailleurs. I am thinking about going with something inbetween 36 to 40 teeth for the largest chainring. – tiadeo Apr 13 at 18:49
  • A ring that small is way outside the normal scope of a road bike. You may have compatibility issues with an MTB crank that's supports rings that small and the road bottom bracket (MTB BBs are wider, cranks have longer axles). I wonder if going to a full SRAM Apex 1x system might actually be an easier way to get the low ratios you are looking for. Might not be more expensive too if you sell the Tagra group. – Argenti Apparatus Apr 13 at 18:58
  • BTW, rear derailleur cable pull and actuation ratios are well documented, I've never seen equivalent info for the front. – Argenti Apparatus Apr 13 at 19:00
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    This isn't really intended to be a road bike. More a gravel/randonneuring bike with drop bars and STI shifters for hilly terrain. I'd be willing to change the crank and BB to accomodate such low gearing. – tiadeo Apr 13 at 19:11
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With doubles this sort of setup can usually be made to work reasonably well. There's at least one bike I know of on the market with the exact setup you describe, the 2019 Salsa Fargo Tiagra, and it does work. Putting a triple STI on a mountain front triple crank and derailleur is where it gets bad.

  • This looks good. With this in mind I will try to use an MTB derailleur. – tiadeo Apr 22 at 21:31
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Why not install a larger cassette on the rear? I have a full 4700 road bike. The rear derailleur is a 4700 GS. It easily accommodates a MTB 11-34 and stretches out to 11-36. I run the 11-34 on gravel trails. Front end is 50/34. 11-36 cassette with 50 - 34 goes up steep hills. 34 -36 combination is almost so high, if you are not careful you can fall off going so slow forward.

MTB's have a different seat tube angle to roadies. MTB derailleurs are shaped to cater for the different angle. As you havew mentioned 4700 is a new 10 speed cable pull ratio. You "might" get away with using a XT 11 speed derailleur "might".

If you have a braze on FD, changing to smaller chain rings might not let the FD to get low enough.

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    This is more of a comment on the question than an answer (hence the downvotes), but brings up a relevant point - does the OP really need gear ratios that low? – Argenti Apparatus Apr 19 at 13:33
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    I am already running my rear derailleur out of spec with a 11-36 cassette. And with a bikepacking setup and me preferring to spin I do need lower gear ratios. My FD is clamped on, so no problem there. – tiadeo Apr 19 at 14:01
  • This is more a bunch of (quite relevant) comments than an answer to the original question. – Criggie Apr 20 at 23:15

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