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I wish to adapt a triple crankset on a gravel frame. I already have the 3x Tiagra ST-4703 brifter. I have different solutions :

  1. get a road triple crankset (Tiagra or Stronglight impact) with a Tiagra front dér
  2. get a MTB triple craknset (like a Deore Trekking 26-36-48) with a Tiagra front dér
  3. get a MTB triple craknset (like a Deore Trekking 26-36-48) with a MTB front dér

As far as I know :

  1. should work, but I am not sure a Tiagra crankset could fit on my frame (due to granny ring size) and I guess the frame is more supposed to work with MTB chainline with its 142 mm thru-axle rear wheel
  2. would be my favorite, but I am not sure the Tiagra FD cat reach the larger ring due to chainline
  3. needs a travel agent : I already have it, but I would have like to get rid of it to make the cable routing more simple

What do you think of these possibilities ?

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  • What’s the current setup of the frame? A better solution might be to use a double with a wide range rear cassette
    – Paul H
    Jan 13 at 15:56
  • I do not have the frame yet. I will order it shortly. I wish a triple, because I already have most of the components (except crankset), especially brifters. I always have problem with double chainrings : it is for me the association of a too small with a too large chainring, so I too often need to shift the FD.
    – rvil76
    Jan 13 at 16:41
  • There's a much larger variety of doubles available geared specifically towards gravel frames these days (e.g., 44-30). A triple really does seem like the worst of all worlds here.
    – Paul H
    Jan 13 at 17:26
  • I understand your point. The bike is supposed to receive a double or simple later (in 1-2 years). Then the triple will be transferred on another bike. This can look weird, but right now I cannot really find available components to build the bike I want.
    – rvil76
    Jan 13 at 17:33
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Putting a 48-36-26 with a road triple FD that's contoured for a 50t usually shifts acceptably.

The 50mm intended chainline of the HT2 mountain cranks will indeed probably go beyond what the FD-4703 can handle in the big ring. (I don't know that I've actually seen this combination attempted though.)

Gravel bikes are a category with a lot of different designs out there in terms of chainstay length, tire clearance, and just generally how the drive side chainstay is done.

If chainstay clearance with the new crank wasn't a potential issue, a good solution here would indeed be get something forged and square taper like the Stronglight crank you mentioned, or a Sugino with the same 48-36-26, or basically any good quality forged 110/74 crank. Then you could bring it in as needed to get the 45mm chainline the FD wants. (Note that 110/74 is originally a mountain standard, back in the dawn of time.)

45mm front chainline will generally work well with a 142 rear end presuming you're pairing this with something like an 11-34 or 11-36. However, the reason it's never that simple is that chainstay length makes a big difference. If it's a bike with aggressively short chainstays you could get into the territory of getting hard or impossible to mitigate FD cage rub in gear combinations you might want to use. But probably not.

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