Jasion Thunder

The Amazon listing and Jasion's own product page mostly agree, and where they do not, the difference matters:

• Motor: the listing says only "1800W Peak". Jasion's page describes "a 750W (peak 1800W) motor". The rated figure is the one state law cares about, so it is useful that the maker publishes it, even if the Amazon title does not. Earlier marketing for the same bike, including a November 2025 Gadget Flow write-up, called it 1500 W peak, so the peak number has drifted while the rated one is the maker's.
• Torque: 85 Nm on both.
• Battery: 48 V 18 Ah, which is 864 Wh, removable, on both. Jasion lists a 7-8 hour charge with a 2.0 A charger. That is consistent with the arithmetic: a 48 V charger at 2 A puts in roughly 110 W, and 864 Wh / 110 W is just under 8 hours.
• Speed: the title and the first bullet say "30+ MPH". The fourth bullet says the five assist levels run "from a gentle 10 mph cruise to an exhilarating 28 mph". The listing disagrees with itself; Jasion's page sides with 30+.
• Weight and fit: 82 lb and a rider height of 5'2" to 6'3", from Jasion's spec table. The Amazon bullets give neither.
• Drivetrain and controls: seven-speed Shimano, cadence sensor, twist throttle, five assist levels and a color display, per Jasion.
• In the box: Jasion lists two fenders and a rear rack. The listing warns that "accessories/gifts may ship separately".

A cadence sensor switches power on when the cranks turn rather than measuring how hard you push, so assist arrives in steps rather than in proportion to effort. That is normal at this price and worth knowing if you are coming from a torque-sensing bike.

Most states use the three-class system. Class 1 is pedal assist to 20 mph, Class 2 adds a throttle and still stops at 20 mph, and Class 3 is pedal assist to 28 mph, with a throttle not allowed in most states. Every class is capped at 750 W. The federal consumer-product definition of a low-speed electric bicycle in 15 U.S.C. § 2085 is also written around a 750 W motor and a motor-only top speed under 20 mph for a 170 lb rider.

Jasion's 750 W rated figure would fit. The speed does not. A bike advertised at 30+ mph with a twist throttle sits above Class 3 on speed and outside it on the throttle, so as sold the Thunder is not a street-legal e-bike in any state that uses the class system. One spec catalogue files it as "Class 4", which is not a legal category anywhere. In practice that can mean it is treated as a moped or motor vehicle, with registration, insurance or licensing rules that a bicycle does not carry, and it is not welcome on bike paths or trails that admit only Class 1 or 2.

There is a partial fix. The Gadgeteer reports that the Jasion app lets the rider set the top speed and the per-level speed limits, and that out of the box the full speed was available in every assist level. Setting a 20 mph cap brings the riding speed in line with Class 2. It does not give the bike a class label from the maker, so check what your state requires on our street-legal-by-state guide, and read Class 1, 2 and 3 e-bikes explained if the categories are new to you. If a class-legal Jasion fat bike is what you want, the Jasion EB5 MAX at $579.99 (as of Oct 30, 8:10 AM EDT, subject to change) publishes a 750 W rated motor and a 28 mph Class 3 top speed, with a smaller 720 Wh battery.

48 V x 18 Ah is 864 Wh. E-bikes use roughly 15-30 Wh per mile depending on rider weight, speed, assist level, tires and terrain. An 82 lb bike on 4-inch tires with a throttle and a 30 mph top end spends much of its time in the upper half of that band. So:

• 864 Wh / 30 Wh per mile = about 29 miles (throttle-heavy riding at speed, or soft ground)
• 864 Wh / 20 Wh per mile = about 43 miles (moderate assist on pavement)
• 864 Wh / 80 miles = 10.8 Wh per mile, which is what the "80 miles" claim requires

That last number is below what a heavy fat-tire bike uses outside the lowest assist level with a light rider on flat ground. The 80-mile claim fails its own arithmetic. Our planning figure is about 35 miles, fewer in cold weather, on sand or snow, or with a lot of cargo.

The Gadgeteer's reviewer wrote that his usual rides of around 20 miles left four of the five battery bars showing. That is a good sign for unhurried riding, but a bar gauge reads battery voltage, which falls slowly at first, so it is not a range measurement and we do not multiply it out. For how range figures are built, see how far can an e-bike go.

The listing says the bike is "backed by UL certification" and does not name a standard or a testing lab. Jasion's product page does not name one either; some of its product photos carry a generic "UL certified" badge with no standard or certificate number. The Gadgeteer's spec list, written from the sample Jasion sent, names UL 2849, the standard for the complete e-bike electrical system. We could not find a certificate to confirm it, and UL 2271 (the battery pack standard) is not mentioned anywhere we looked.

That gap matters if your building, landlord or city requires UL 2849 for indoor charging. Ask Jasion for the certificate number and the lab before you buy, and see our e-bike battery fire safety guide for what to check. If documented certification is non-negotiable, the Funhang Fat 26 ($529.99 as of Oct 30, 8:10 AM EDT, subject to change) names SGS for UL 2271 and TÜV for UL 2849, and the step-through Vivi ACE07 ($703.61 as of Oct 30, 8:11 AM EDT, subject to change) carries an SGS-issued UL 2849 mark. Both are Class 2 fat bikes with smaller batteries.

The listing describes a "passenger-ready frame" that "welcomes your child, furry companion, or a loved one", and Jasion's page says the heavy-duty rear rack carries "gear, groceries, or a passenger". Neither publishes a load rating for the rack itself, and neither lists a passenger seat, footrests or a handhold. The 400 lb payload has to cover the rider, the passenger and anything else on the bike, so two adults can exceed it.

We would not put a person on a standard rear rack. A child needs a child seat rated for that rack, and a pet needs a carrier made for bikes. Many state vehicle codes also bar carrying more people on a bicycle than it is designed and equipped for, so a passenger on a bare rack can be a ticket as well as a fall risk. If carrying a passenger is the point, look at bikes built for it in our family e-bike guide.

Brakes: dual hydraulic discs, listed as "180mm Dual Hydraulic" in The Gadgeteer's spec list. The listing's "2-second braking" claim gives no starting speed, so it cannot be checked. The Gadgeteer's reviewer wrote that he did not feel confident in the braking power, that the brakes lacked an initial bite and felt squishy, and that he had to plan his braking in advance. That is worth knowing on a bike that weighs 82 lb before a rider and is advertised at 30+ mph.

Throttle: a twist grip on the right bar. The same reviewer reported the bike creeping forward when he was at a standstill, and that he once put it into walk assist mode by accident, which left him pedalling with no motor help until he spotted the icon on the display. Neither is a defect report from more than one owner, but both argue for learning the controls somewhere quiet and keeping assist at zero while you get on and off.

Frame and suspension: a low step-through frame ("High Carbon Steel Step-Through" in The Gadgeteer's spec list; Jasion's page does not state the material), an adjustable front fork with 80 mm of travel per the same list, which Jasion says locks out, and no rear suspension. The Jasion Thunder Pro is a separate, full-suspension model.

Extras: headlight, brake light and turn signals are standard, and the listing describes ride tracking and a "remote security lock" without explaining how the lock works. The Gadgeteer's reviewer finished basic assembly in under 30 minutes and praised the instructions.

Warranty: the listing promises 24 months on the motor, battery and controller. Jasion's own store says all Jasion bikes carry a 1-year warranty and sells an extra year as an add-on. If the longer term is part of why you are buying, save a copy of the listing and confirm it with Jasion in writing.

Buy the Thunder if you ride on private land, farm tracks, beaches or snow, want a step-through fat bike with a large removable battery, and either do not need class status or will cap the speed in the app and check your state first. Within Jasion's range it sits between the 720 Wh EB5 MAX and the 1,040 Wh EB5 Ultra on battery size, and it is the step-through option of the three.

Skip it if you need a bike you can show is Class 1, 2 or 3 for paths, campus or a building's rules (the EB5 MAX or the Vivi ACE07 fit that brief), if you need documented UL 2849, if the bike has to go up stairs at 82 lb, or if you plan to carry a passenger. For more options, see our best fat-tire e-bikes under $1,000 and, if speed is the draw, the fastest e-bikes on Amazon, which explains the same class problem for every bike on it.