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Touring bike which is running XT M-8000 double crankset. It is geared too low. Chainrings are 36t and 26t with cassette ranging from 11t to 40t. I don't think the other M-8000 double chainring option of 38t and 28t will make much of a difference.

  1. Is it possible to swap these chainrings for the 40t and 30t chainrings normally associated with the XT M-8000 triple crankset?

  2. Is there an option with a different cassette?

  3. Are there other alternatives?

Thanks!

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  • what front derailleur do you have and is it a direct mount version (as opposed to band type)
    – Nathan Knutson
    Commented Jan 13, 2022 at 0:18
  • the big question here to me is whether the spacing is going to come out correct if you did this. the right arm/spider design is different between the triple and double version, and I don't know whether the rings have any crank-specific thickness/spacing things happening.
    – Nathan Knutson
    Commented Jan 13, 2022 at 19:22
  • It's shimano xt m8025 2×11 speed, high clamp, dual pull. It can be raised or lowered. Gear shifting on this one is friction.
    – bitsofbikes
    Commented Jan 13, 2022 at 19:30
  • @Nathan Knutson. You are correct. Using the triple chainrings isn't an option. The 40 tooth chainring is bolted onto the outside of the crank. See a diagram here: [link](dassets.shimano.com/content/dam/global/cg1SHICCycling/final/ev/… )
    – bitsofbikes
    Commented Jan 13, 2022 at 19:53
  • Strange that there don’t seem to be any bigger chainrings than 38t available (can’t find any on the whole internet). I’m wondering if there is an engineering reason for that. You are right that going from 36t to 38t would only be a 5.5% improvement in speed (at the same cadence) for a topspeed of ~50km/h at 110rpm.
    – Michael
    Commented Jan 13, 2022 at 21:16

2 Answers 2

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I'm thinking to another alternative, that I give for reference as I can totally understand that moving from XT to Deore/Alivio is a downgrade. But if you can't have exactly what you want, you have to make compromises and this compromise will depend at the end of you priorities.

There is a 46/30 chainring in the Alivio range (FC-MT210-2). It's rated for 9-speed, so using it with a 11-speed chain can be a big stretch. I'm personally using that crankset with a 10 speed configuration (FD-M3000 front derailleur, RD-M5120 rear derailleur, 11-42 cassette).

A bit more far stretched: the Giant Roam Disc 0 (not available in all markets) uses a M8000 XT in combination with a 46/30 chainring in 11 speed. If your LBS can order Giant parts, it might interesting to see if they can order that chainring as spare part.

If you go for this option, you'll also need another front derailleur. The options are quite limited there also: Microshift FD-M622G-B (used by the Giant Roam 0).

Otherwise, I mention it for reference: 68mm bottom brackets start to be used on hybrid/touring bikes. It's worth checking because, in that case, it opens the possibility of using a 46/30 GRX crankset (FC-RX600-11) and remain with your XT for the rear derailleur. You will probably need a GRX front derailleur though (I think the pull ratios are the same for road and MTB front derailleurs, but am not sure. If it's confirmed, you can keep your shifter, otherwise you'll need to find a shifter for flat handler bars with road pull ratios).

But before using a 46/30, it's important to check the frame clearance. Even more with GRX cranksets that they have a chainline slightly closer to the frame.

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  • it's a surly long haul trucker with a 68mm bottom bracket (Shimano XT MT800 MTB Bottom Bracket). Using GRX looks like a real possibility: link
    – bitsofbikes
    Commented Jan 14, 2022 at 16:29
  • The link you gave is about GRX to XT, which is "never" a problem: with spacers, you can fit a MTB crankset on a road bike. The problem is the other way around: you can't fit a crankset designed for a 68mm BB on a bike that has a 73mm + road chainrings are larger, so there may not be enough frame clearance. In that case, this post is more useful: bicycles.stackexchange.com/questions/75445
    – Rеnаud
    Commented Jan 14, 2022 at 16:39
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You could consider using one of 9t small cog XD driver cassettes, like the e*thirteen XCX 9-39 as an example. The problem with that is if you find yourself using the small end of the cassette a lot, you will wear them out fast. The small cogs are replacable, but there's still the hassle of doing it, and if you wear out the second-smallest etc then it's a costlier proposition. Still though, getting a higher gear without changing anything up front is the problem those exist to solve. You'll need to get to an XD driver somehow, either a replacement freehub or a new wheel/hub.

Ultimately if this is a high-mileage bike and you need higher gears, a new crank is probably the more practical thing. Then you have a lot more options to get the gearing you really want.

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