Biktrix Juggernaut Ultra Duo 4 Step-Over Review: 160 Nm of Torque for Steep Climbs for $3,499
This $3,499 fat-tire off-roader pairs a monster mid-drive motor with a big 910Wh battery for riders who actually head deep into rough country.
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What the stars are rated against
The stars compare this bike with other off-road e-bikes we have scored — 32 of them, priced $1,750–$5,249. They are a ranking inside that group, not an absolute grade: four stars means it beats most of that set on the measure, not that it hits some fixed standard.
Peers are drawn from a tight price band around this bike, so a $1,000 commuter is judged against other $1,000 commuters rather than against machines costing three times as much. Change the group and the stars would change with it.
The headline Genius Score is not decided by that group alone. It blends the category ranking above with a market-wide view across every bike we publish, so a bike cannot climb simply by sitting in a weak category. How we score.
If your idea of off-road means real backcountry, steep and loose climbs, snow, sand, or a fire road that turns into a rock garden, the Biktrix Juggernaut Ultra Duo 4 Step-Over is built to keep going where lighter bikes tap out. The heart of it is a motor with that drives the bike through its gears instead of just shoving the rear wheel, so it hauls a loaded bike up nasty grades without bogging down.
You get a too, so you can ride up to 20 mph without pedaling, which helps a lot when you're crawling away from a dead stop on something technical. A big 910Wh keeps you out for long days. The shifting and brakes are more ordinary than a $3,499 price tag might lead you to expect, though.
Pros & cons
What we like
- A 1000W Bafang Ultra M620 with gives it real climbing muscle, and because it works through the gears, steep and loose is where it feels strongest.
- The 910Wh is big enough for long backcountry days, and the frame will take a second pack if you want to stretch a day trip into an overnighter.
- A lets you pull away without pedaling up to 20 mph, which is a genuine help for tricky starts partway up a climb.
- A 380-pound rating leaves plenty of room for cargo, a trailer, or hauling a heavy load back out.
- It runs 26x4 fat tires for snow, sand, and gravel, or narrower 27.5x3 MTB tires when you want to roll faster on hardpack and pavement.
Worth weighing
- The 180mm rotors are on the small side for a machine this heavy and this powerful; on long, loaded descents, larger rotors would shed heat and keep their bite better.
- For $3,499, the Shimano Alivio 9-speed drivetrain is fairly basic for the price.
Key specs
The motor & power
The Bafang Ultra M620 is one of the strongest motors you'll find on a production e-bike. It's rated at with and , and because it drives the crank rather than the wheel, it multiplies its pull through whatever gear you're in.
That's exactly what you want when the trail kicks up and gets loose. On a steep, technical climb it keeps digging instead of stalling, and it launches a heavy loaded bike from a standstill without any fuss.
As it ships, the bike is set to , so it has a and tops out at 20 mph whether you pedal or use the throttle. In that mode the software also caps power at 500W. You can reprogram it in the settings to unlock the full output for off-road use, and that's where all 160 Nm really comes into play.
Out of the box the Juggernaut is limited to 20 mph and 500W, which keeps it legal as a Class 2 bike on public paths and roads. The full 1000W, the 1,500W peak, and higher speeds live behind a settings unlock and are meant for private or off-road land. Riding it unlocked on public paths can push it out of legal e-bike territory, so check your local rules before you flip it over.
Range & battery
The included 910Wh (52V, 17.5Ah) is a large pack, and Biktrix quotes on a charge.
That 95-mile figure is a best case on easy ground with light assist. On the steep, soft terrain it's built for, the real number lands noticeably lower, so plan your rides around a more conservative distance and you won't get caught short of the trailhead.
If you regularly ride far from an outlet, the frame accepts a second battery for a combined 52V 34Ah, roughly 1,794Wh. That's a serious reserve for all-day trips well off the grid.
Biktrix's spec page lists a whole menu of battery sizes, everything from 728Wh up to 1,092Wh and beyond, because the pack is an upgrade option. This Duo 4 as configured includes the 910Wh internal battery. The bigger numbers are either paid upgrades or the combined total once you add a second pack.
Ride & components
The Juggernaut is set up to run two very different tire choices: 26x4 fat tires that float over snow, sand, and loose gravel, or 27.5x3 MTB tires that roll faster on hardpack and pavement. Which pair you fit changes the feel of the bike more than almost anything else you can adjust.
The 380-pound gives you room to load up racks and panniers for a multi-day trip without brushing the limit.
It's a big machine at about 88 pounds with the battery, which is in line with other fat-tire off-road bikes this size. Stopping comes from Biktrix dual-piston on 180mm rotors, which are fine at everyday trail speeds but work hard on long, loaded descents.
Shifting is handled by a Shimano Alivio 9-speed drivetrain. It's dependable and easy to live with, though it's a modest piece of kit next to the motor it's bolted to.
Price & value
At $3,499, the Juggernaut Ultra Duo 4 sits firmly in premium off-road territory, and it earns a Genius Score of 71 out of 100. That reflects strong capability, with value the softest part of the picture.
You're paying for the two things that matter most out here: a top-tier motor and a large battery. That's the right place to spend on a serious off-road bike. The trade-off is that the drivetrain and brakes are more mid-pack, so if you were hoping the whole build matched the motor, it doesn't quite get there.
For a rider who actually uses that power on hard terrain, it's money well spent. For someone whose trails are mellow, you'd be paying for muscle you'll rarely call on.
Who it's for
The backcountry climber
If your rides mean real elevation and loose, technical ground, think mountain fire roads, rocky pitches, and deep sand, this is exactly the tool. The and its keep pulling where a lesser motor would stall, and you can lean on the to get rolling again after a stop.
The load-it-up explorer
If you head out for the whole day with camp kit, fishing gear, or a hunting load, the 380-pound and the large 910Wh are built for it. You can cover real distance fully loaded and add a second pack when a day trip stretches longer.
The bike-path gravel rider
If your off-road is mostly flat gravel paths and easy dirt, this is more bike than you need. You'd be spending $3,499 for climbing power you'll almost never use, and a lighter, cheaper fat-tire bike would fit that kind of riding better.
The strictly-public-paths rider
If you'll only ever ride marked bike paths and public roads, you'll keep it capped at 20 mph and 500W to stay legal, which means the full 1000W and 160 Nm mostly sit idle. You're paying a premium for capability that only really pays off on private or off-road land.
Frequently asked
Does the Biktrix Juggernaut Ultra Duo 4 Step-Over have a throttle?
Yes. It has a , so you can ride up to 20 mph without pedaling. That's a big help for pulling away from a stop on a steep climb, though riding on the throttle uses up the battery faster than pedaling.
How far does the Biktrix Juggernaut Ultra Duo 4 Step-Over go on a charge?
Biktrix claims from the 910Wh . That's a best case on easy terrain, so expect a good deal less on the steep, soft ground it's made for. You can add a second battery to nearly double the capacity.
What class is the Biktrix Juggernaut Ultra Duo 4 Step-Over?
It ships as a bike, with a throttle and a 20 mph limit. It's also programmable, so you can unlock more power and speed in the settings for off-road or private-land use.
How much torque does the Biktrix Juggernaut Ultra Duo 4 Step-Over have?
It makes from its Bafang Ultra M620 mid-drive motor, which is among the highest you'll find on a production e-bike and the reason it climbs so well under load.
How much does the Biktrix Juggernaut Ultra Duo 4 Step-Over weigh?
About 88 pounds with the battery installed, which is normal for a fat-tire off-road bike with a motor and battery this size.
What's the payload capacity of the Biktrix Juggernaut Ultra Duo 4 Step-Over?
It's rated to carry 380 pounds, so a heavier rider plus a full load of gear or cargo is well within its limits.
How it compares to its siblings
Same 160Nm torque and 380 lb payload as the Ultra Duo Pro Step-Thru, but in a step-over frame at $3499 — a real premium just for the frame swap. It claims a far longer 95 mi range despite a smaller 910Wh battery, but the brakes drop to dual-piston 180mm from the Duo Pro's quad-piston 203mm setup. Get this over the Step-Thru only if you need the step-over geometry or the fat/MTB tire choice (26x4 or 27.5x3); otherwise the Step-Thru has better brakes for less.
Biktrix Juggernaut Ultra Duo Pro Step-Thru review Biktrix Juggernaut Ultra Eagle 2 review Biktrix Juggernaut Ultra FS Pro 3 Cruise review Biktrix Juggernaut Hub Duo Step-Over 2 review
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Biktrix Juggernaut Ultra Duo 4 Step-Over is ranked on:
Guides worth reading
- Mid-drive vs hub motorWhere the motor sits changes how the bike climbs, what it costs, and what wears out. Neither is better everywhere.
- E-bike classes explained: Class 1, 2 and 3Three classes, two questions: does it have a throttle, and how fast does the motor keep helping.
- Nominal vs peak watts on an e-bikeThe wattage in the headline is usually the peak figure, which can be roughly double the number the motor actually sustains.
How we score: the Genius Score blends a bike's capability against same-price peers with its value for the money, weighted for what this off-road buyer prioritises. Specs are pulled from the manufacturer's live page and normalised (nominal vs peak watts, true weight with battery). Ratings are our estimate from specs, not a lab test.