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  1. #1
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    Tandem / Fatbike Convergence

    No, I'm not building a tandem fatbike. Or at least I don't think so yet.

    But I am thinking about a tandem. Which leads me to tandem hubs, which makes me think that there's a bunch of possibilities for wider hubs from the fatbike world. But that also means wider chainlines in the back.

    I'm pretty sure this bike will never swap wheels with anything else, and I'm pretty sure it will have disk brakes. So should I go 135 in the rear? 135 offset dishless? 150 tandem? 170 fatbike?

    There's also the question of how fatbike freehubs would take tandem loads. So maybe it's a dumb idea.

    And for the front, go 135 just because?

    This tandem will be lightly offroaded. It will probably be 29er, though maybe 650b now that it's 27.5.

    I'd ask in the tandem group, but it gets very little traffic.

  2. #2
    will rant for food
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    I'd ask Fatback about their 170 hubs - this is a vague memory but I seem to recall them being picky about their freewheels.
    Latitude: 44.93 N

  3. #3
    tiny rider
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    Just thinking about the wheel size, I would expect going as big as possible would be beneficial.

    I have a 26" mtn tandem that has been used for touring and such over the past decade, and I can't really claim it's flickable, or that the wheels accelerate particularly quickly. I've often had a suspension seatpost in back to try to smooth things out a bit for the stoker, and imagine bigger wheels would only make the ride back there smoother.

    There is something to be said for replacement availability if you are somewhere remote, but that's the only point I can think of in favor of a 26" wheel/tire combo with standard hubs.

  4. #4
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    For a 170 rear there's a few "tandem quality" free hubs. The Paul hub uses an I9 driver and the Hope can be upgraded to the burly steel trials freewhub. But unless you are going with fat rubber that would require a wider bb, you'd be creating a goofy chainline for a marginally stronger rear wheel.

    As far as wheel strength, I think a 135mm spaced front hub would be beneficial with discs and 700c rim. The hitch there is that benefit would be erased if you are wanting to use and off the shelf fat bike fork, as they are all massive and noodly as hell. Now if you are building your own 135 spaced tandem fork....
    Slowly slipping to retrogrouchyness

  5. #5
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    I had a 26" wheel tandem and I'm definitely going bigger. I have plenty of 29" tires so that could cross over easily. Going 650 would mean a shorter fork, lower disc brake loads, and a little easier chainstay fitting, and there's plenty of tires from the Hetres over to full on freeride tires.

    For the rear hub I'll probably just watch eBay and see what fate hands me in the not-stupid-chainline department. It's going to be a while until this project gets going.

    I will be building my own fork, so it can be 135. I plan on having this frame come apart in two pieces so it can go in the back of the Subaru, so I'm not worried about roof-racking it.

  6. #6
    will rant for food
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    Quote Originally Posted by dr.welby View Post
    No, I'm not building a tandem fatbike. Or at least I don't think so yet.
    Technical issues aside...

    DO IT.
    Latitude: 44.93 N

  7. #7
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    I'd do a 150mm hub (and I'd assume that all 150mm hubs are disc). Of course, I'd get a CK with the stainless drive shell and with a Maxle, you'd be in good shape on the back. I wouldn't think that 170mm would help enough to make a huge difference and then you have to run some strange bb shell for the stoker. 83mm isn't so strange for the stoker though there is the question of what you'll do for cranks... I like the idea of the 135mm front hub. Paul?

  8. #8
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    Quote Originally Posted by dr.welby View Post
    I had a 26" wheel tandem and I'm definitely going bigger. I have plenty of 29" tires so that could cross over easily. Going 650 would mean a shorter fork, lower disc brake loads, and a little easier chainstay fitting, and there's plenty of tires from the Hetres over to full on freeride tires.

    For the rear hub I'll probably just watch eBay and see what fate hands me in the not-stupid-chainline department. It's going to be a while until this project gets going.

    I will be building my own fork, so it can be 135. I plan on having this frame come apart in two pieces so it can go in the back of the Subaru, so I'm not worried about roof-racking it.
    35er tandem would be the shznick Pauls hubs and Sram 11 speed!!!
    PAYASO 36er.....Live the Circus

  9. #9
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    I've had a bug to see if the 12x142 conversion would play nice with my Hope 135mm spaced front hub. Combine with Paragon 142x12 hooded rear dropouts and you have a nice fatfork.
    Slowly slipping to retrogrouchyness

  10. #10
    Nemophilist
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    Quote Originally Posted by G-reg View Post
    I've had a bug to see if the 12x142 conversion would play nice with my Hope 135mm spaced front hub. Combine with Paragon 142x12 hooded rear dropouts and you have a nice fatfork.
    Dooood!

    I've been wijjuz on that thought. Long time. That would be a worthwhile trickle-over to Fatties from other realms. Along the same lines, I've been wondering about making a shorter fork to see if I could reduce the twist/flex a bit. If it worked, I'd go "un-corrected" on my next frame.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  11. #11
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    I think Salsa's new fat carpet fibre fork is T/A, and there's at least one other company with a T/A 135mm fork on the way. Which means there's bound to be some hubs around sooner than later too.

    Hacking off two-ish inches from an Enabler is what made me start thinking about a T/A short/fat fork.
    Slowly slipping to retrogrouchyness

  12. #12
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    Quote Originally Posted by G-reg View Post
    Hacking off two-ish inches from an Enabler is what made me start thinking about a T/A short/fat fork.
    Hmmm, that's an good idea...

    On to other things, what sort of tubing dimensions are used these days, especially for the open frames? I need to go measure my friend's Co-motion next time they come visit.

  13. #13
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    Quote Originally Posted by dr.welby View Post
    On to other things, what sort of tubing dimensions are used these days, especially for the open frames? I need to go measure my friend's Co-motion next time they come visit.
    Paging Mr. Whipsmart!

    I could probably ask him if you want to get tube specs sooner.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  14. #14
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    No hurry, and I should add that the stoker compartment is going to be long enough that I'll have to use plain gauge tubing for the boom and stoker top tube.

  15. #15
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    I got some rough numbers, seems like the Co-Motion has:

    31.8 seat tubes
    40mm down tube
    1.5" top tube
    2" boom tube.

    Unfortunately .035" seems to dry up after 1.5", so the boom will have to be .049.

  16. #16
    The cat's name is jake
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    I don't check in very often (not for lack of interest, I just get busy), but I saw my name!

    I might know a little bit about tandem tubing - here are some general specs:

    Down tubes on frames with laterals are 1.5
    Down tubes on "lateral-less" frames vary between 1.75 - 1.875 depending on model
    Top tubes on frames with laterals are 1.375
    Top tubes on frames without laterals vary between 1.5 - 1.75
    Seat tubes vary from 1.25 - 1.375
    Boom tubes vary from 1.75" to 2"
    Tube profiles vary from crazy thin to fairly unsurprising.
    True temper has some pretty nice 1.75 plain gauge .035" material, in long sections.

    I said nothing. you don't know me.

  17. #17
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    0.049 isn't a bad thing. Despite extra bracing, it is ~twice as long as a single. When I was at Bike Friday, some of the couplers were made of .093 plus, depending on the rider weights.

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