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  1. #1
    Join Date
    Sep 2007
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    3,351

    Drivetrain recommendation

    I recently purchased a used bike to primarily get the frame for my wife. The bike came with a few parts that I'm going to steal - at minimum, a set of XT 4 pot brakes.

    It also came with an XT 12-speed shifter and RD and an e*thirteen helix 9-50 cassette. I have e*thirteen 11 speed cassettes (9-46) on my current mountain bike, my hardtail, my wife's mountain bike, my gravel bike and possibly her gravel bike as I build it up this winter.

    The advantage to running the 12 speed, wider range drivetrain is that I can run a bit larger chainring (currently on 28t and could go with 30 or 32 with similar gearing). From what I keep reading, that should help the suspension kinematics.

    The advantage to sticking with the 11 speed is that it's common across all of our bikes. If one drivetrain goes down (shifter, derailleur, cassette) I can swap off of another bike.

    So I guess my question is: does the range (therefore improved suspension performance), shifting performance, etc. of the newer 12 speed stuff outweigh the convenience of having commonality across most of our bikes?

    Sent from my SM-N986U using Tapatalk

  2. #2
    Join Date
    Jun 2020
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    1,407
    From a kinematics standpoint, moving to a larger chainring isn’t necessarily an improvement, it’s just a change. Whether that change is for the better or worse depends on where you’re starting, and where you want to go.

    Larger chainring is going to decrease the anti-squat of the suspension. Is that good? Well, if you’re getting too much bob already when climbing on relatively smooth trails, it could increase that bob further, decreasing the climbing efficiency (I’m assuming any bob is coming from too little anti-squat instead of too much, since that’s the much more likely scenario). Conversely, more anti-squat - from a smaller chainring - will reduce the responsiveness of the suspension a little while under load in low gears, so if you’re looking for a bit of extra traction when climbing a rooty/rocky tech section, the bigger ring may help.

    Pedal kickback will be reduced with the larger ring, so if you’re frequently taking big hits at low speed, that may be a benefit, especially if your rear hub has very fast engagement and the bike has lots of travel. Conversely, if your big hits are happening at high speeds, on a bike with moderate travel, and using a hub with a lower number of engagement points, you may not notice any difference at all.

    ETA: Suspension kinematics considerations should all be secondary to choosing a chainring that actually provides the range of gearing you want/need. Putting a larger chainring on to marginally increase suspension performance on steep tech isn’t going to help you if you now struggle to actually keep the pedals moving. And the change in suspension feel changing chainring size by 2 teeth is going to be pretty small.
    Last edited by J. Barron DeJong; 01-15-2022 at 11:17 AM.

  3. #3
    Join Date
    Dec 2007
    Location
    Hell Track
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    11,798
    I find that the usefulness of having the same number of gears on every bike exists, but isn't huge. However, I find the usefulness of having the same hub driver on every wheelset is more significant. Putting aside discussions of which drivetrain I like better, I wish I had either all XD or all microspline, rather than a couple of both. In other words, I swap wheels around a lot more than I swap individual drivetrain components.

    The whole discussion of kinematics is going to vary significantly from bike to bike. Some bikes will play nicely with variations in chainring size. Some won't. And for whatever it's worth, variations in cassette sprocket size changes the antisquat too. Depending on the bike, the cassette changes might be more significant than changes in the chainring size.

  4. #4
    Join Date
    Sep 2007
    Posts
    3,351
    Thank you both. All good things to consider and helpful when thinking about the suspension performance. I guess my thoughts about "better performance" was mainly based on statements that I've read suggesting that the manufacturers design around specific chainring sizes. I can see the point about that not necessarily being optimal for all use cases, however!

    Toast, I ended up buying a second Rowl (M) as the large was just a little too large for Sarah. However, when I rode it, I really liked it and decided to keep both (and sell my V1 hightower). When I rode it it had a 26t chainring with 9-46 cassette.

    As I know you are personally familiar with this particular design, what are your recommendations? It seems like it might be hard to figure this out on paper as there will be changes in both chainring and cassette. I remember feeling like the bike was very efficient as I had it set up - it climbed really well and felt great on the descents.I could see some value in improving the small bump compliance which would suggest a larger ring.

    When I'm thinking of swapping drivetrain parts I'm mostly thinking about keeping bikes up and running. As an example, on a trip to Moab last spring, my group ended up needing to pilfer parts from another bike we had along. Most were not really specific to drivetrain except that I toasted my rear hub and luckily was able to find a rear wheel with an xd driver. This happens here at home also as I have one bike or another go down with one problem or another.

    On that note I agree on the driver - I have converted (or am in the process of converting) all of our (adult) bikes to xd(r).

    Seth

    Sent from my SM-N986U using Tapatalk

  5. #5
    Join Date
    Mar 2008
    Location
    northern BC
    Posts
    26,918
    Chain ring has a bigger effect on gearing than cassette, dropping chain ring teeth is the easiest/ cheapest way to get up the hills and remember that messing with this stuff will likely call for a different length and/or new chain
    Lee Lau - xxx-er is the laziest Asian canuck I know

  6. #6
    Join Date
    Dec 2007
    Location
    Hell Track
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    11,798
    Quote Originally Posted by sethschmautz View Post
    Thank you both. All good things to consider and helpful when thinking about the suspension performance. I guess my thoughts about "better performance" was mainly based on statements that I've read suggesting that the manufacturers design around specific chainring sizes. I can see the point about that not necessarily being optimal for all use cases, however!

    Toast, I ended up buying a second Rowl (M) as the large was just a little too large for Sarah. However, when I rode it, I really liked it and decided to keep both (and sell my V1 hightower). When I rode it it had a 26t chainring with 9-46 cassette.

    As I know you are personally familiar with this particular design, what are your recommendations? It seems like it might be hard to figure this out on paper as there will be changes in both chainring and cassette. I remember feeling like the bike was very efficient as I had it set up - it climbed really well and felt great on the descents.I could see some value in improving the small bump compliance which would suggest a larger ring.

    When I'm thinking of swapping drivetrain parts I'm mostly thinking about keeping bikes up and running. As an example, on a trip to Moab last spring, my group ended up needing to pilfer parts from another bike we had along. Most were not really specific to drivetrain except that I toasted my rear hub and luckily was able to find a rear wheel with an xd driver. This happens here at home also as I have one bike or another go down with one problem or another.

    On that note I agree on the driver - I have converted (or am in the process of converting) all of our (adult) bikes to xd(r).

    Seth

    Sent from my SM-N986U using Tapatalk
    Eluder is probably a better person to ask about the kinematic changes with swapping rings / cassettes around on the Rowl. That said, on that bike I think the anti-squat numbers (and pedal kickback) increase as you decrease the size of the cassette cog and the chainring. So going to a smaller cog on the cassette together with going to a smaller chainring will increase the anti-squat numbers at sag. I would expect that to induce some bobbing, as the chain forces will probably extend the suspension a bit while pedaling. So yeah, moving towards a larger range cassette paired with a larger chainring will keep the anti-squat at around 105-110% at sag, which is probably what the bike was designed around (and, in my opinion, is a pretty good range to be in for pedaling efficiency).

    When I had it, I was running a 10-50 cassette and at various times ran a 30, 32 and 34t ring. With sag at 25%, I thought it pedaled fine and had pretty good small bump sensitivity. Best pedaling efficiency was probably with the 34t, but the 30t wasn't terrible, and it's certainly less painful on steep climbs.

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