Unicorn search? Off-road fat step-through + internal hub?

[ColinC]

Hello!

I’m looking for what might be unicorn, but wanted to see if anyone has ideas/suggestions. I’m a backcountry nature photographer/trail camera enthusiast and have been using a BBSHD-converted fat tire e-bike for several years now to get to rough/remote locations. I’ve spent enough time on that bike to realize that my ideal backcountry e-bike would have the following:

1. Step-through frame (maybe a frame design like this) that is strong enough for 275-300lb rider+ gear weight over rough/bumpy terrain
2. Mid-drive, at least 750w, not torque-sensing, and ability to add throttle (user-adjustable assist levels + throttle like BBSHD are perfect for me/my riding)
3. Belt rather than chain drive (this is the least important of my criteria)
4. Tubeless-optimized fat tire wheels
5. Internal hub rather than a derailleur, since weeds/grass often clog my derailleur, and I replace hangers 2-3x a year with the leggy derailleur getting abused by rocks, logs, etc.

I’d need a quiet internal hub. I upgraded my current BBSHD conversion to an Onyx rear hub to eliminate that pawl clicking, which has been great for the kind of “in nature” riding I do. I’m guessing no internal hub is that quiet, but from video of the Rohlhoff, I can say that would definitely be too loud for what I want. If there are no reasonably quiet internal hub options, I’ll probably just scratch that idea and live with cleaning the weeds/grass out of the derailleur and the annual derailleur replacement.

If such a bike doesn’t exist, what would be the best strategy for assembling one? Perhaps finding a bike that meets 1.-4., then switch out the rear wheel for a custom rear wheel build with an internal hub (assuming a reasonably quiet one exists)?

 

[RunForTheHills]

Step-through frame, belt drive, and IGH aren't features you'll find on trail/mountain bikes. Although the frames tend to have low sloping top tubes that are easy to step over. That can make it harder to find a place to mount a battery. Lots of city and commuter bikes have those features. Consider giving up the fat tires. If you are not riding around on loose sand, they don't do much for you that a suspension doesn't do better and they create rolling resistance.

 

[Chalo]

Alfine 8 has a silent clutch, but won't hold up to BBSHD with gearing low enough for trail use.

Enviolo and NuVinci are also quiet hubs, with better ability to transmit BBSHD power without fracturing.

If a normal freewheel ratchet is too noisy for you, understand that fat tires are at least that noisy when rolling. You should already have perceived this.

 

[ColinC]

Well, this set of features (or many of them) is relatively common in e-bikes for hunting, which although I'm not hunting, is pretty close to my use case--much more so than typical trail/mountain biking. I'm carrying considerable weight (a backpack and a rear rack pack) with cameras, batteries, etc., and I'm seldom on trails...so it's right through the grass/weeds/brush and over all sorts of surfaces. I'm off and back on the bike dozens of times during my ride, often with boots and heavier pants in winter, making getting up over a higher top tube less and less fun as the day goes on. I've not ridden non-fat tires in these conditions, but the fat tires have served me well. And I assume there's a good reason most of the hunting e-bikes run them

 

[ColinC]

Alfine 8 has a silent clutch, but won't hold up to BBSHD with gearing low enough for trail use.

Enviolo and NuVinci are also quiet hubs, with better ability to transmit BBSHD power without fracturing.

If a normal freewheel ratchet is too noisy for you, understand that fat tires are at least that noisy when rolling. You should already have perceived this.

Thanks for the input on the clutches/hubs. And very true as far as fat tire rolling noise when on gravel roads (I don't ride on pavement, but obviously true there too). But for the surfaces on which I ride (seldom on trails, let alone well-packed trails), and at the speeds I do (relatively slow), the noise from fat tires is minimal

 

[RunForTheHills]

I am not sure then. Perhaps start with one of those hunting ebikes and modify it to fit your needs. This bike seems to check a lot of your boxes: Atlas

Alternatively, you could start with a frame made for a Bafang m600 (Ultra) motor and build it with the components you want on it. To support a belt drive, the rear fork needs to have a split for servicing the belt. If you use a rear hub motor, you won't have the option of using an IGH.

 

[ColinC]

I am not sure then. Perhaps start with one of those hunting ebikes and modify it to fit your needs. This bike seems to check a lot of your boxes: Atlas

Alternatively, you could start with a frame made for a Bafang m600 (Ultra) motor and build it with the components you want on it. To support a belt drive, the rear fork needs to have a split for servicing the belt. If you use a rear hub motor, you won't have the option of using an IGH.

You're right; that Atlas does check a lot of boxes. While as deep a step-through as others, it looks like the TT slopes down more than my current bike for a reduced step-over. I'll need to take a closer look at the low-end gearing; I watched a video last night from a cross-country adventurer who had good things to say about Shimano Alfine, but felt that its low-end was not up to any adventuring that involved climbs due to the inadequate low gearing. And he hinted at what Chalo said about concerns with ebike power demands/use. Obviously not a fat tire bike, but it could be that fat width is overkill/not truly necessary for my riding...and looks like there's a Maxxis Minion in this size.

Thank you for bringing the Atlas to my attention!

 

[scianiac]

What is the maximum speed you ride, the only thing that matters is the gearing range of the hub, if you don't go particularly fast you can just reduce the input gearing to any hub to get a much lower low gear.

 

[ColinC]

What is the maximum speed you ride, the only thing that matters is the gearing range of the hub, if you don't go particularly fast you can just reduce the input gearing to any hub to get a much lower low gear.

18-20mph tops, and that's just on a few gravel road downhills. Most of the ride it's much slower than that...