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  1. #1
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    Gear systems on fatbikes.

    In another thread we're discussing the merits or otherwise of offset chainstays. Those of us who like hub gears are wanting to retain them.

    The unasked question is - Why would anyone want a hubgear when there's a far better range of gears available with a cassette?

    So I thought I'd address that here,
    and here's a few pics of some typical rides for me.

    When I ride on a trail it's usually to get somewhere interesting, and once at the somewhere interesting, there's usually no trail or if I'm lucky a 2" wide trace left by deer or sheep. As a result there's often a lot on on and off with the bike, dragging it through thick heather or undergrowth or up a minor rockface.

    Anything that sticks out gets hung up at some stage.




    Deer fences have to be crossed - lifting is always a bit difficult for me because of residual weakness from a bout of Guillaine-Barre paralysis






    Dense heather is demonically tricky. It can wangle its way in anywhere, but it's really tough so removing it is a hassle. In this pic it has got into my disk calliper and got caught on the little pad spring, pulled it out and bent it. I've had this happen a couple of times and it's one of the reasons I have drum brakes now.




    In this next picture, the heather was really cunning. I'm about 3-4 miles from any trail and been on and offing the bike every 50 metres or so.




    And this was the result. Lost pedal. Despite searching closely I never found it and had a 19 mile one legged pedal home. (OK it was a QR pedal, but it had never come loose before)





    Just about any ride will find me in places like this. Dense heather with concealed rocks and bogholes. I doubt I could keep a derailleur unbent or attached to the bike for long in this stuff.





    And on a ride last month, I had the heather/disk problem again when out hunting iron age settlements (they obviously didn't have bicycles back then, there's no trails to them ) Fortunately this one was closer to home.




    And to finish off, I've seen a derailleur freeze solid from the slush on it when the rider stopped to fix something else. Probably not a problem for the Alaskans with their much lower temperatures.
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  2. #2
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    What is your low gear in gear inches?
    Riding Fat and still just as fast as I never was.

  3. #3
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    Quote Originally Posted by crashtestdummy View Post
    What is your low gear in gear inches?
    When I have the hub gear on, low gear is 22" with a 32/22.

    My single speed fatbike is on 32/20 (46") for dry trails and for wet weather 32/22 (42"). If I'm mainly going to be riding on deep snow or bogs with the single speed then I use 22/22 (29").
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  4. #4
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    I've done some bog hopping and bush whacking. I am interested in a hub gear

  5. #5
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    Agreed. I am a huge fan of my Rohloff for all the points you mention.

  6. #6
    Elitest thrill junkie
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    Seems to me it would be better to design the hub in the frame, like some of the ones in this mega-thread: the gearbox thread

    Also like this Nicolai Argon AM:



    If you are designing a new bike and intending for a gearbox or internal hub, putting it in the rear wheel is shooting yourself in the foot. A gearbox or internal hub should be in the frame. Less mass further from your center of mass, ability to have hub/gearbox more protected, less cable length and consequently cable drag, etc. Not that you shouldn't put an internal hub on a 135 bike, go for it if you like, but if you are truly sold on internal gears, this would be the way to go.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  7. #7
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    Your's is beautiful countryside Velobike! In my area we're not allowed off trail as much as you are there (though we get away w/ it in some isolated places). Except in Winter on snowmobile tracks and open sand in some areas. And riding muddy trails here is frowned apon due to the damage it leaves behind for others (in some types of soil, your tracks will harden like concrete when it dries out). Different worlds brother...

    Also many miles of really steep "jeep track" here in the Cascade Mountains... I use my 20/36 quite often. I'll measure the gear inches on a fat bike tonight.

  8. #8
    Randomhead
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    really nice post. In terrain like that your loose parts need streamers like powder skiiers use on their skis. Probably don't have to be quite as long though. I almost lost a ski once in fresh powder even with a 30 foot streamer.

  9. #9
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    Quote Originally Posted by ward View Post

    Also many miles of really steep "jeep track" here in the Cascade Mountains... I use my 20/36 quite often. I'll measure the gear inches on a fat bike tonight.
    What hub is your 36 on?
    Riding Fat and still just as fast as I never was.

  10. #10
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    Quote Originally Posted by Jayem View Post
    Not that you shouldn't put an internal hub on a 135 bike, go for it if you like, but if you are truly sold on internal gears, this would be the way to go.
    I'm sold on IGHs for fatbikes and my explorer type MTBs. But I'm not sold on the Pinion system at this point. I've posted my reasons over in the IGH Forum Pinion threads. So I wouldn't be interested in the extra cost and the lack on compatibility with my other bikes.

    The Rohloff in my Krampus lived in a different 29er MTB before it and will live in a number of frames after it. I can sell my old IGH frames to pretty much anyone since they accept derailleurs just fine.

    In theory I agree with you that having the weight centralized would be ideal, but it's not something I think is worth the cost and specialization that the Pinion requires.

    Personally I don't notice the rearward weight bias on my IGH bikes in use.
    Safe riding,

    Vik
    www.vikapproved.com

  11. #11
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    Quote Originally Posted by vikb View Post
    ...Personally I don't notice the rearward weight bias on my IGH bikes in use.
    Nor do I.

    The ability to slot in a single speed wheel is more important than centralising mass. (I don't do any aerial stuff).
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  12. #12
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    Quote Originally Posted by crashtestdummy View Post
    What hub is your 36 on?
    It's a derailleur system, not IGH. 20 small chain ring and 36 low on cassette. "crawler"!

    I'll measure the gear inch's tonight when I get home for comparison.

  13. #13
    Dr Gadget is IN
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    Yes, hubgears have some definite advantages - especially in rough conditions.

    On my 3x9 Fatback, my low gear is 16" - which is at least nominally outside the torque spec for a standard freehub ratchet! But it's great for creeping up and thru steep and technical routes.

    My hubgear Moonlander has a Sturmey Archer S3X, with a 36x16 drive and a low of 41" - but it's more about the fact that it's a fixed gear and how it's ridden than about being a hubgear. Fixie with 3 ratios? Couldn't resist!

    I have seen arguments for the Rohloff being much stouter than the recommended drive ratio/torque limit - things like it's use on tandems, where the torque can be doubled. I have a speedhub languishing on a recumbent, where a more efficient derailer drivetrain would make more sense, but that's a whole 'nother project
    This isn't a "you're doing it wrong" topic.

    WSS/OSS: Open Source Sealant

  14. #14
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    FWIW - my Rohloff is geared at 34T x 16T which is the lowest "legal" ratio for a single rider. That ratio limit applies to Olympic athletes and world cup racers. So there is definitely some room to go lower safely.

    The hub itself has a torque limiting safety feature that will fail before any real damage is done and you can have your Rohloff restored to full function should you trigger that safety mechanism. So far I haven't read of anyone reaching that limit.

    34T x 16T at the Rohloff's gear #1 transmission ratio of 0.279 = 34/16*0.279 = 0.59
    32T x 16T at the Rohloff's gear #1 transmission ratio of 0.279 = 32/16*0.279 = 0.56
    30T x 16T at the Rohloff's gear #1 transmission ratio of 0.279 = 32/16*0.279 = 0.52

    A 20T chain ring and 36T cassette cog gives you a ratio of = 20/36 = 0.56

    The stock Pugsley comes with a 22T x 32T low gear of 22/32 = 0.69

    Your actual gear inches will vary with wheel size.

    I haven't felt the need to go lower than 34T x 16T on my Rolhloff, but I would have no concerns going to 32T.
    Safe riding,

    Vik
    www.vikapproved.com

  15. #15
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    Quote Originally Posted by wadester View Post
    ...I have a speedhub languishing on a recumbent, where a more efficient derailer drivetrain would make more sense, but that's a whole 'nother project
    I think I've been spoilt by singlespeed. I can't stand the noise/feel of my Rohloff which is why I use Alfine for my hubgear.

    Should really get it on a fatbike though. The ability to climb walls is useful.
    As little bike as possible, as silent as possible.
    Latitude: 5736' Highlands, Scotland

  16. #16
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    Quote Originally Posted by Velobike View Post
    I think I've been spoilt by singlespeed. I can't stand the noise/feel of my Rohloff which is why I use Alfine for my hubgear.
    Oh yeah. Riding on smooth pavement, the whir of the "low range" reduction in the lower 7 gears is very obvious.

    Quote Originally Posted by Velobike View Post
    Should really get it on a fatbike though. The ability to climb walls is useful.
    Definitely yeah!
    This isn't a "you're doing it wrong" topic.

    WSS/OSS: Open Source Sealant

  17. #17
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    I agree with VeloBike's rationale for using IGHs. They match up well with exploration type rides.



    I frequently find myself riding through thick vegetation where I can't see debris, sticks, rocks that want to damage my bike.



    I'm often carrying, pulling, pushing and throwing my bike over or down things and pulling it under or up obstacles. With a loaded bike and frequently slippery terrain my bike gets beat up.



    The other thing I really enjoy is my IGH's immunity to weather/dirt. It will shift as well on a dry sunny day after it's been cleaned as it will covered in mud for 3 days on tour.



    Living on the beach for 2 months I lubed my chain once. Covered in rust and sand the chain just kept going round and the IGH shifted same as always.



    Frequently my adventure bikes get crammed into the back of a truck surrounded by gear and bounced down some craptacular roads. Not having any delicate drivetrain components makes that process less risky and I don't have to pack with the utmost care.



    I'm a happy derailleur user on my other bikes. So it's not about IGH zealotry. I just use what I consider the best tool for the job at hand.

    Safe riding,

    Vik
    www.vikapproved.com

  18. #18
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    Vik...Rohloff has revised their low input torque rating; it is now 36/17 = 2.117647058>

    Thanks for the write-up VB.

    Not long ago I was toying around with the idea of a remote mounted Rohloff for the purpose of getting a better balance in the choice of gear inches...while the bottom is most likely enough...there are too many 'wasted' upper gears the way I ride. Also I do not know what gear would be useful against strong gusty headwinds on the beach. (40mph+?)

    It would also allow the use of wider hubs, and remove the IGH completely from the possibility of immersion and with some shielding, from tire spray. (salt water)

    I gave up on it due to the thought of too much drivetrain resistance with my then idea of using two chains; that and too many custom made parts.

    Maybe have to revisit the idea using a single chain and three sprockets. (?)

    Is the noise in the lower 7 gears really all that bad? My remote idea places the hub somewhere on the seat tube, and behind it, THAT could amplify it!?

    One thing I am uncertain of is: 36 Chain ring + an adapted 36 chain ring at the rear wheel + a 17T cog at the IGH...does the overall ratio still equal 2.11>?

  19. #19
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    Quote Originally Posted by Sand Rat View Post
    Vik...Rohloff has revised their low input torque rating; it is now 36/17 = 2.117647058>

    Is the noise in the lower 7 gears really all that bad? My remote idea places the hub somewhere on the seat tube, and behind it, THAT could amplify it!?
    From the Rohloff site:

    The primary sprocket ratio used with the Rohloff SPEEDHUB 500/14 (e.g. 42:16) converts the slow rotational speed at the crank into a fast rotational speed at the rear sprocket and reduces the input torque for the Rohloff SPEEDHUB 500/14 in the same proportion. To prevent overstraining the hub, a minimum factor of 2.10 must be used. This minimum factor equates to a primary transmission ratio of:- 36:17, 34:16, 32:15 and 28:13. These SPEEDHUB 500/14 ratios resemble a derailleur transmission of 20:34.
    Larger chainrings can be used without exceptions.
    2.10 is the minimum input ratio, but since my Rohloffs have all come with 16T cogs I use them. I'm not particularly worried about going below that number. I am not an exceptionally powerful rider.

    Practically I don't notice the noise from my Rohloffs or the vibration in the lower range. I'm typically crunching over rocks, sticks, dirt, etc...

    My Rohloffs coast silently and there is no chain noise which is nice.
    Safe riding,

    Vik
    www.vikapproved.com

  20. #20
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    I am new to IGH bikes and do notice that 7th gear is noticeably noisier than all other gears. I only have about 400k's on the hub at this point so I hope things will settle in after a decent period. I am also using gates belt drive and find it super smooth generally.. In saying that, on the beach I do get a squelch in the same spot in every revolution?

  21. #21
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    Quote Originally Posted by ads-bully View Post
    I am also using gates belt drive and find it super smooth generally.. In saying that, on the beach I do get a squelch in the same spot in every revolution?
    I've found that (and there has been a video posted here before on this topic, can't remember who) the belt drive is pretty nice except in large-grain damp sand, it simply cannot clear gunk as fast as a chain.

    I have a pet project to mash as many of the good parts and as few of the bad parts of IGH and conventional cassettes into one form. It's not a new idea. I wanted it done by this year but that isn't happening as I've switched gears (lawl) and taken vikb's advice for the time being. I think dense drivetrain stuff belongs in the middle, and I can feel the bias a bit especially after having ridden my very fun but draggy Hammerschmidt dinglespeed bike.

    I'd also much rather fast-swap entire rear wheels than change rear tires, and I don't want to pay for a second or Nth IGH for the number of tires I want on a given bike.

    I like the lack of zealotry in this thread. The coolest drivetrain I've ridden so far was a bike equipped with XX1. Super awesome. I just hold some of the same opinions as vikb but I'm... also a... well, a major klutz.
    Latitude: 44.93 N

  22. #22
    Dr Gadget is IN
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    Re: Rohloff noise. If you can hear tire noise as you ride - you can't hear the hub noise over it. But, if you're on smooth pavement with high pressure tires, you can hear it, especially when you shift between 7 and 8. whole lot of whirring going on as things get where they're going. 8 is actually 1 without the range reduction, so you're going from top to bottom on the 7 spd main and engaging or disengaging the reduction gearset that makes gear 8 into gear 1. Can't feel it in your legs, and I note that it gets quieter with run-in.

    Quote Originally Posted by Sand Rat View Post
    Not long ago I was toying around with the idea of a remote mounted Rohloff for the purpose of getting a better balance in the choice of gear inches...
    Google "G-boxx rohloff" and you will find others with the same idea, but mainly for long travel/DH use. Fun stuff. Mid mounting the Rohloff would take some of the torque load off it, and proper selection of drive and driven ratios would let you get the most use out of the available range. I would actually prefer to have a couple of extreme creeper gears in the neighborhood of 0.6:1, or 16"gear. This would bring the high end down as well, make it more useful for general riding.
    This isn't a "you're doing it wrong" topic.

    WSS/OSS: Open Source Sealant

  23. #23
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    Thanks Wadester...did a quick search and look...interesting...cranks on the hub.

    Thanks also on the noise concerns.

  24. #24
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    off topic: @vikb how short did you take your chain with the zee derailer (big > big +2 links was real loose on the little cog for me)

    on topic: I just had a 23T cog arrive for my Alfine8, I've been running a 22T but thought going to a 24T would be too far. Goes a little something like this....

    Gear systems on fatbikes.-fatbike.png

  25. #25
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    Quote Originally Posted by OFFcourse View Post
    off topic: @vikb how short did you take your chain with the zee derailer (big > big +2 links was real loose on the little cog for me)
    I just installed the derailleur and ran the chain through to test fit it and then cut it to length.
    Safe riding,

    Vik
    www.vikapproved.com

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