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  1. #1
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    Dropped Chainstay thoughts

    With the prevalence of larger tires for gravel bikes, I'm seeing many production carbon frames going to a dropped drive-side chainstay. In my latest iteration for my own gravel bike, I've gone to MTB cranks to get chainring clearance with a 29x2.0 tire. And I thought, why not drop the chainstays similar to a wishbone seatstay design (I've seen several of this design, most recently from TiCycles), but using an extended down tube as the tie-in point for the chainstays? The idea is to be gain tire clearance and stay with road-width cranks... Anyone have any experience with a similar design? Thoughts, concerns, warnings, predictions of armageddon? I've attached some computer model concept shots I threw together this morning.

    Dropped Chainstay thoughts-dropcs1.jpgDropped Chainstay thoughts-dropcs2.jpgDropped Chainstay thoughts-dropcs3.jpg

  2. #2
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    Nice concept.

    regards. Brian

  3. #3
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    I guess there might be issues with chain interference if it's dropped too far...

  4. #4
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    Biggest downsides are:
    1: Chainslap in some cases. Depends on the ring and how much you're dropping the chainstay(s).
    2: Whole structure is a bit less stiff/rigid.
    3: Bit of a pain to build, though nothing horrible.

    I have to admit to being a bit baffled by the whole concept of gravel bikes with 2"+ tires and super short chainstays. For a mountain bike, sure, you want short stays sometimes to allow bunnyhops/manuals/etc and to make tight turns/control total wheelbase. On a gravel bike you want *long* stays (along with a super low BB) - it's intended to be comfortable/smooth/efficient, and you never need to manual off a drop.

    I generally try to talk gravel bike customers into the longest stays I can do - 450+mm. At that point 2" tire clearance is easy without any funny stuff needed.

    -Walt

  5. #5
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    Quote Originally Posted by Walt View Post
    On a gravel bike you want *long* stays (along with a super low BB) - it's intended to be comfortable/smooth/efficient, and you never need to manual off a drop.



    -Walt





    Agreed, you want a limousine to smooth out the chop imho.
    "These things are very fancy commuter bikes or really bad dirt bikes, but they are not mountain bikes." - J. Mac

  6. #6
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    My current (in process) build uses 435mm chainstays and judicious dimpling, along with MTB cranks for clearance.

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    If you plan on running a front derailleur make sure you have room for it

  8. #8
    pvd
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    I hate dropped stays.

    FYI, this bike doesn't use dropped stays, 420mm stays, uses road cranks, 622-57 tire, 49mm chainline, large sprocket. It can be done.

    Also, I wouldn't bother trying to go too big in the back. My new bike will only go to 622-45 rear tire and 2x drivetrain. Big tires and drop bars don't mix.

    Hybrids are back! | Peter Verdone Designs


  9. #9
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    Quote Originally Posted by Walt View Post

    ....I have to admit to being a bit baffled by the whole concept of gravel bikes with 2"+ tires and super short chain stays.....

    I generally try to talk gravel bike customers into the longest stays I can do - 450+mm. At that point 2" tire clearance is easy without any funny stuff needed.

    -Walt
    Ditto.

    Brian

  10. #10
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    I agree with PVD and Walt.

    For me, if it's drop bars that means high speed pedaling, which means aero/group riding for miles, which means non-technical riding, which means ~70mm of trail or less, which means i can't make proper use of more than a ~38mm tire. I mean, not exactly, but you get the idea. Rides where i want drop bars rarely coincide with rides where i want properly high volume tires.

    I built a traditional road bike for myself with 420mm chainstays and room for 42c tires. I offset the chainstays 5mm and seat tube 9mm to make it fit with room for a fenders and dropped chain. Everyone is different but i just see compromises beyond this point, not further optimization or potential.


    My opinion doesn't matter if your riding makes that design sensible, in which case i'd be psyched to see it, and see it in action.
    "Things that are complex are not useful, Things that are useful are simple."
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  11. #11
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    I actually set out to build a mtb with a dropped drive side chainstay to try and avoid using a yoke. Didn't work, for me anyway. Turns out the triangular space between the tire, chainring, and chain is incredibly small. Especially when the chain is on the smallest cog in back, and that lower loop of chain comes up pretty high.

    I was using a 32t cog in front, 1x12 drivetrain, so you might have more room in there if you have a larger front ring.

    If you manage to pull it off, post pics.
    Myth Cycles handbuilt bike frames
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  12. #12
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    Quote Originally Posted by Walt View Post
    On a gravel bike you want *long* stays (along with a super low BB) - it's intended to be comfortable/smooth/efficient, and you never need to manual off a drop.

    I generally try to talk gravel bike customers into the longest stays I can do - 450+mm. At that point 2" tire clearance is easy without any funny stuff needed.

    -Walt
    Are you building gravel bikes with unusually slack seat angles, or unusually long front-centers?

    I've always figured the long stays are a hallmark of comfort because they're typically paired with a slack seat angle. I'm always annoyed when the rear axle is so far behind me i can't unweight the front wheel as the terrain dictates. Long = comfortable flex (or less lever on my butt...?) always seemed like an academic point; i can't really feel it.

    As always, thanks for fielding my questions!
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  13. #13
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    short chainstay FTW

    Sent from my SM-G955F using Tapatalk

  14. #14
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    btw it seems same company do drop chainstay for gravel bikes:


    Sent from my SM-G955F using Tapatalk

  15. #15
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    Quote Originally Posted by scottzg View Post
    Are you building gravel bikes with unusually slack seat angles, or unusually long front-centers?

    I've always figured the long stays are a hallmark of comfort because they're typically paired with a slack seat angle. I'm always annoyed when the rear axle is so far behind me i can't unweight the front wheel as the terrain dictates. Long = comfortable flex (or less lever on my butt...?) always seemed like an academic point; i can't really feel it.

    As always, thanks for fielding my questions!
    It has nothing to do with seat tube angle, it's just the basic idea that the further away from the axle you sit, the less your butt gets moved up and down as the wheel encounters bumps.

    If you ever sat at the back of the school bus you know how this works.

    -Walt

  16. #16
    Jan
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    OPEN WI.DE. with both chainstays dropped:

    Dropped Chainstay thoughts-open-wide-gravel-bike_carbon-fat-tire-gravel-bike_off-road-adventure-gravel-bike_dt-swiss-grc140.jpg

  17. #17
    pvd
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    Stay focussed on the important stuff and design around that. Focusing on overly large tires is not as valuable as decent geometry. You don't need over 45mm rear tires in this class but you do need something that is designed to work.

    Airspeeder! | Peter Verdone Designs


  18. #18
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    Curious question PVD.

    You're running 1200mm plus Wheelbase and 98-101mm trail here.

    I have felt that for some time that you would venture into Motorcycle Geo at some point and therefore the whole feel of the bike will reflect that.

    My experiments have suggested that the bike of this design is running a little too un-responsive steering wise, particularly with narrow drop bars at the lower speeds a human powered bike can do compared with assistance (engine). I find that the bike also feels kind of Top Heavy, and needs body language to steer - that is a leaning technique.

    How are you finding this balance?

    Eric
    If I don't make an attempt, how will I know if it will work?

  19. #19
    pvd
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    The bike is rad. It handles great. A little bit of the traditional road bike feel will be sacrificed when it's designed for dirt use but doesn't make it bad. It's so much better everywhere. A modern road (criterium) bike is useless almost everywhere.

    I just need modern drop bars to be produced to use on the Airspeeder. That's the big problem currently. The Bird of Prey worked with those limitations.

    Also, we use wide drop bars these days. I'm looking for some good 48 or 50cm bars.

    So many myths exist in popular fiction about bike design as told my magazine and marketing shills. Ive been doing a lot of work in the past few years that attacks that.

  20. #20
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    Certainly agree with the wider drop bar.
    I laugh at the fads of the press about design.
    Each year they seem to get excited about common sense and if I look back at comments from a decade ago....it seems so infantile.
    Geo is actually very simple once it is fully understood. But it takes time to grasp.
    Keep experimenting.

    Eric
    If I don't make an attempt, how will I know if it will work?

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