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I am getting a new bike (Giant Revolt Advanced 3) and because of GRX being completely out of stock I am not able to upgrade the GRX400 that comes with it. I will have to do it later. Since I have a Shimano XTR Shadow 2008 groupset in very good conditions, my idea was to mount this group but only with two chainrings. This way I can sell the GRX400 parts and not lose that much money since I do want to upgrade whenever becomes possible.

Now, my question is if there is any way of having brifters (Sora?) working with XTR 9 speed mechs and at the same time compatible with the existing hydraulic disk brakes (GRX400)?

If I must guess I think this may be an impossible mission but not Tom Cruise style, with some kind of workaround possible.

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  • There are ways to use hydraulic disc brakes with cable operated brake levers. The Trickstuff Doppel Moppel comes to mind. But it’s expensive and probably hard to get these days. Why didn’t you get the bike with GRX-600 or 810 if you want a better groupset? – Michael Mar 29 at 9:54
  • Thanks for the reply. Because of color choice but mostly because of availability. Where I live, the model with GRX600 would probably be available only for August or even past it. :/ – Carlos Meireles Mar 29 at 12:37
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    Unfortunately, upgrading the groupset isn't likely to be cost effective. I realize availability is a concern, but a) I fail to see how 2008 XTR is an upgrade over GRX 400, and b) how would 9s Sora STI levers, even if you could make them work with the other components, be an upgrade? – Weiwen Ng Mar 29 at 12:41
  • It would not be an upgrade. I want to upgrade once GRX600/800 becomes available. My intention was to make this group useful and not waste the GRX400 that comes with it since my intention is to sell it. – Carlos Meireles Mar 29 at 16:01
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    (continues) Sora shifters was just a way of trying to put all things working. Since what I had in mind is not possible, would it be possible at least to use the XTR crankset? Keeping in mind that GRX400 is 10 speed and XTR is 9 speed? I don't know if I could be using any more component. – Carlos Meireles Mar 29 at 16:15
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It may be best just to leave the bike as is, and simply knock a hundred bucks or two off the groupset for wear when you sell it. Better than

  • A: having to buy a bunch of other parts which will also have to be sold,
  • B: potentially riding a janky setup for months which isn’t guaranteed to shift well nor be very reliable with all the cobbled-together parts,
  • C: putting wear and tear on your soon-to-be vintage XTR groupset when you can’t even enjoy using it to its full extent, and
  • D: your time and effort to do two complete groupset swaps.
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There is no hydro STI that can do the first idea. It would need to be an old cable pull 10 but hydro, and that doesn't exist.

The first obstacle with your FC-M970 in BB86 idea is even if you jank it together with spacers, the bearing contact areas of the spindle won't be in the right place. Also you'll be taking a component where one of the reasons it's so expensive in the first place is the machine work done to remove material everywhere possible, and then you'll be adding extra leverage to the spindle in a place it wasn't designed to take it. Someone may make a conversion BB that does it better, but then you're eating into the money you're trying to save.

Providing you solved the above, published chainline for FC-M970 is 50 and 46.9 for GRX 2x10 rear ends. So you can make that work if you accept having bad chainline. You are also sacrificing Q and will be spending money on rings that play nice with a road FD, or accepting bad performance of ones that don't.

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    Thank you guys for enlighten me. Reading your point of views made me realize I was just overthinking the whole thing. Better stay as it is and think only about upgrading the wheelset for now. – Carlos Meireles Apr 1 at 0:40

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