The VIVI FM20UL is a 20″ x 2.4″ fat-tire folding electric bike designed to do double duty: compact enough for apartments and car trunks, but powerful enough to handle city streets, bike paths, and light off-road detours. With a 1000W peak brushless hub motor (65 Nm torque), a 48V 7.8Ah (374Wh) battery, and a true folding frame + folding stem, it’s built as a portable urban utility bike rather than a big, heavy full-size fat-tire rig.
As a VIVI Ebike referral partner, I earn commission from qualifying purchases.
👉 See current details and color options for the VIVI FM20UL on the official VIVI site.
TL;DR – VIVI FM20UL at a Glance
| Category | Details |
|---|---|
| Bike Type | 20″ x 2.4″ fat-tire folding electric bike, urban/utility focus |
| Motor | 1000W peak brushless hub motor, 65 Nm torque |
| E-Bike Class | Class 2 (pedal assist + throttle, up to ~22 mph) |
| Battery | 48V 7.8Ah (374Wh) removable lithium-ion |
| Claimed Range | 22–25 miles throttle only, 44–50 miles with pedal assist |
| Realistic Range | Plan on about 18–35 miles depending on weight, terrain, and assist level |
| Max Speed | Up to 21.7 mph (35 km/h) / ~22 mph |
| Bike Weight | About 55 lb (25 kg) |
| Max Load | Up to 330 lb (rider + cargo) |
| Tires | 20″ x 2.4″ anti-puncture “fat” tires, 30 TPI |
| Frame & Fork | 6061 aluminum alloy step-over frame, coil suspension fork (60mm travel) |
| Brakes | Mechanical disc brakes, 160 mm rotors |
| Drivetrain | Shimano 7-speed (14–28T freewheel) |
| Riding Modes | Pure electric, PAS, normal bike, walk/assist push, cruise control |
| Best For | Riders wanting a portable, folding fat-tire bike for commuting, errands, and light trails |
👉 Check the official FM20UL spec tables and geometry on the VIVI product page before you decide.
Key Specs: VIVI FM20UL Technical Overview
| Spec Category | VIVI FM20UL Details |
|---|---|
| Model | FM20UL |
| Colors | Black / White |
| E-Bike Class | Class 2 |
| Motor | 1000W peak brushless hub motor, 65 Nm torque |
| Battery | 48V 7.8Ah (374.4Wh) removable lithium-ion battery |
| Controller | 48V 18A brushless motor controller |
| Display | 48V intelligent digital LCD display |
| Charger | US plug 54.6V 2A smart charger |
| Charging Time | 4–6 hours |
| Top Speed | 35 km/h (21.7 mph) max, 25 km/h (15.5 mph) regular speed |
| Max Range | Max 50 miles, PAS 44–50 miles, throttle 22–25 miles |
| Bike Weight | 25 kg / 55 lb |
| Load Capacity | 150 kg / 330 lb |
| Riding Modes | Pure Electric, Pedal Assist, Normal Bike, Assist Push, Cruise Control |
| Waterproof Rating | IP54 |
| Certification | **SGS |
| Frame | 6061 aluminum alloy, step-over |
| Fork | Iron/aluminum alloy coil suspension fork, 60mm travel |
| Drivetrain | Shimano RD-TY200 7-speed, SL-TX50 thumb shifter, 14–28T freewheel |
| Brakes | 160 mm double mechanical disc brakes, front and rear |
| Tires | 20″ x 2.4″ 30 TPI anti-puncture fat tires |
| Geometry Highlights | 63″ total length, 27.2″ standover, 29.1–46.1″ seat height, rider 5’1″–6’3″ recommended |
Design & Frame: Folding Fat-Tire Utility in a Compact Package
The FM20UL is built around a 6061 aluminum step-over frame with true folding capability: the main frame folds and the aluminum alloy stem is retractable and folding, letting you shrink the bike’s footprint for car trunks, RVs, closets, or apartment hallways.
Key design elements:
- Step-over frame – more traditional than step-thru, but still relatively low thanks to 20″ wheels
- Retractable folding stem – drops the handlebar height when folded and helps fine-tune fit when open
- Integrated rear rack rated to 25 kg (55 lb), plus full-coverage fenders
- A relatively short 63″ overall length, which makes it maneuverable in tight city environments
The vibe is “urban utility tool” more than “big beach cruiser”: small enough to live in tight spaces, but burly enough to handle rough pavement, curbs, and light trails.
Motor, Speed & Real-World Power
VIVI equips the FM20UL with a 1000W peak brushless hub motor rated for 65 Nm of torque. On a 20″ wheel, that torque translates into:
- Quick, confident starts at lights and stop signs
- Solid hill performance for most city and suburban use cases
- Enough punch to keep you comfortably at or near the ~22 mph top speed when conditions allow
The spec sheet lists:
- Class 2 e-bike designation
- Regular speed: 25 km/h (15.5 mph)
- Max speed: 35 km/h (21.7 mph)
In practice, you can think of it as a zippy Class 2 folder that feels closer to a small moped than a mellow cruiser when you open it up.
Because it uses a cadence-based assist:
- The motor kicks in when the sensor detects your pedaling and adjusts based on PAS level
- Higher PAS levels feel strong and lively, but riding at max assist and speed will drain the 374Wh battery faster
Battery, Charging & Realistic Range
The FM20UL uses a 48V 7.8Ah (374.4Wh) lithium-ion battery mounted inside the frame and removable for charging or storage.
VIVI’s range claims:
- Throttle (Ebike) range: 35–40 km / 22–25 miles
- PAS range: 70–80 km / 44–50 miles
- Max range: 80 km / 50 miles (best case)
With a 374Wh pack and a strong hub motor, those numbers are achievable under light, ideal conditions. For most riders, a more grounded expectation is:
- 18–25 miles if you lean heavily on the throttle, ride fast, or tackle a lot of hills
- 25–35 miles if you mostly pedal in PAS 1–3, ride at moderate speeds, and stick to flatter routes
Charging takes about 4–6 hours with the included 2A smart charger.
If you think of this as a one-charge-per-day commuter for trips up to ~15–20 miles plus errands, you’ll rarely run into range anxiety. Longer days are still doable with a mid-day top-off at home, work, or your RV.
Folding, Portability & Storage
As a folding bike, portability is part of the FM20UL’s value proposition:
- Folding frame + folding stem reduce both length and height, making it easier to store behind a car seat, in an SUV trunk, under a workbench, or in a small apartment corner
- At about 55 lb, it’s lighter than many full-size fat-tire e-bikes, but still not a “carry it up several flights of stairs daily with one hand” bike
Most practical scenarios:
- Rolling it into elevators and folding by your desk or in a storage area
- Transporting in an RV, van, or wagon as a “last-mile” vehicle
- Stashing it in tight garages or shared storage spaces alongside cars and other gear
If you expect to carry it upstairs regularly, consider whether 55 lb plus bulk fits your reality.
Ride Quality, Suspension & Tires
The FM20UL sits on 20″ x 2.4″ anti-puncture fat tires with 30 TPI casing, paired with a coil spring suspension fork (60mm travel).
This combination gives you:
- More grip and cushioning than skinny commuter tires, with enough volume to soften potholes and cracks
- A balance between rolling efficiency and comfort – 2.4″ is substantial but not as draggy as 4.0″ sand tires
- A front end that absorbs bigger hits on rough pavement, cobblestones, or gravel paths
VIVI also highlights dual shock absorption via the front suspension fork and the rear shock-equipped saddle, which helps take the edge off sharper bumps and rougher surfaces.
With sensible tire pressures, the bike feels:
- Stable and planted at typical city speeds
- Nimble enough to weave through traffic or tight bike paths thanks to the shorter wheelbase
The adjustable handlebar and seatpost heights (roughly 29.1″–46.1″ saddle height) help riders from 5’1″ to 6’3″ find a reasonably upright, comfortable position.
Braking, Safety & Electronics
Braking is provided by 160 mm front and rear mechanical disc brakes with alloy levers and motor cut-off switches.
- For a 55 lb, ~22 mph folding bike, this setup is adequate and straightforward to maintain
- Motor cutoffs in the brake levers ensure the hub motor stops driving when you brake, improving safety and control
Electronics and safety features:
- 48V integrated LED headlight and 48V DC integrated LED taillight for visibility
- Waterproof integrated wiring harness and IP54 rating, suitable for light rain and everyday splashes
- 48V LCD display showing speed, assist level, mode, and battery
- Half-twist throttle plus thumb throttle and built-in cruise control for steady-speed rides on long flats
For frequent night or high-traffic riding, you may still want to add:
- A brighter or secondary headlight
- High-visibility clothing and reflective add-ons
Drivetrain, Gearing & Climbing
The FM20UL uses a Shimano 7-speed drivetrain with:
- Shimano RD-TY200 rear derailleur
- Shimano SL-TX50 7-speed thumb shifter
- 14–28T 7-speed freewheel
- 42T chainring and 170mm cranks
Paired with the motor’s 65 Nm torque, this gear range is tuned for:
- Comfortable cadence at 12–18 mph in mid-level PAS
- Climbing typical city grades with motor assist, especially at lower gears and moderate PAS settings
It’s not a super-low gearing setup for extreme hills, but for urban and suburban inclines, it fits the FM20UL’s intended role.
Everyday Use: Commuting, Errands & Light Adventures
Where the FM20UL really shines is day-to-day practicality:
- Commuting: Ride from home to work on a mix of roads and bike paths, then fold and park under a desk or in a corner
- Errands: Use the integrated rear rack (rated to 55 lb) for groceries, bags, or small boxes
- Recreation: Take it on weekend rides, river trails, or park loops—fat-ish tires and suspension handle light off-road well
- RV / van life: Fold it for travel, unfold at campgrounds or trailheads to explore nearby towns and trails
The 330 lb max load, fat tires, and rear rack make it a genuinely useful utility machine, not just a travel toy.
Pros & Cons
Pros
- True folding design (frame + retractable folding stem) for easier storage and transport
- 1000W peak motor, 65 Nm torque – strong for a compact folder
- 48V system with 5 PAS levels and cruise control
- 20″ x 2.4″ anti-puncture tires balance comfort and efficiency
- Shimano 7-speed drivetrain tuned for city and light trail riding
- 55 lb bike weight – lighter than many full-size fat-tire e-bikes
- 330 lb load capacity plus integrated rear rack and full fenders
- Certified to UL 2849 / 2271, GCC, CPSC 1512 for added safety confidence
Cons
- 374Wh battery is modest compared to long-range bikes; heavy throttle and high speeds reduce range significantly
- Mechanical rather than hydraulic disc brakes – perfectly usable, but may need more frequent cable adjustments
- Step-over frame may not be ideal for riders who strongly prefer a very low step-thru
- Folding at 55 lb is still bulky; not ideal if you must frequently carry it up and down stairs
- Motor and battery setup prioritize punch + portability over ultra-long-distance touring
Who the VIVI FM20UL Is Best For
The FM20UL is a strong fit if you:
- Need a folding e-bike that can live in a car trunk, RV, small garage, or apartment
- Want more power and torque than many entry-level folders provide
- Are between 5’1″ and 6’3″ and prefer a compact, upright ride instead of a big 26–29″ frame
- Typically ride short-to-medium distances (5–20 miles per trip) on mixed pavement and light off-road
- Value utility features like a rear rack, fenders, lights, and cruise control right out of the box
In short, it’s ideal for riders who want a portable urban utility e-bike that doesn’t feel underpowered.
Who Might Want a Different Bike
You might want to look at a different model if:
- You routinely ride 40–60+ miles in a day and don’t want to charge mid-ride
- You need a true step-thru frame for maximum ease of mounting and dismounting
- You strongly prefer hydraulic disc brakes or a torque-sensor feel
- You rarely need folding and would rather have a larger frame and bigger battery for similar money
In those cases, a long-range 26″ commuter or full-size fat-tire model may line up better with your priorities.
Final Thoughts: Is the VIVI FM20UL Worth It?
If you’re looking for a compact, folding fat-tire e-bike that delivers strong power, decent range, and real-world utility without taking over your home or vehicle, the VIVI FM20UL lines up well with what its spec sheet promises.
It won’t rival dual-battery adventure bikes for range, but as a folding urban utility machine with a 1000W peak motor, 2.4″ fat tires, and UL-certified electronics, it offers a compelling mix of portability, capability, and value.
