Jasion Thunder Pro

Jasion's own comparison table on the Thunder Pro page puts the two side by side. The Jasion Thunder is the front-suspension original: Jasion lists it with a 48 V 18 Ah (864 Wh) battery, 85 Nm of torque, 30+ mph, a 400 lb payload, an 82 lb weight and a rider range of 5'2" to 6'3". The Thunder Pro moves to a 52 V 20 Ah (1,040 Wh) pack, 115 Nm, 35 mph, a coil rear shock under the seat tube, a 500 lb payload claim and a 96.6 lb weight, with the stated rider range stretched to 5'5" to 7'2". Both use 26 x 4 tires, hydraulic brakes, turn signals and Jasion's app.

So the Pro is the heavier, faster, rear-sprung version, with 176 Wh more battery. By Jasion's own figures it adds 14.6 lb and 5 mph. Neither bike fits a US e-bike class at its advertised speed. Pick the Thunder if weight and a lower minimum rider height matter more; pick the Pro for the rear suspension and the bigger pack. Jasion also sells a Thunder Pro ST with a lowered top tube, which is the version BikeRide tested and the better choice for shorter riders.

No, at any setting. Under the US three-class system, Class 1 is pedal assist to 20 mph, Class 2 adds a throttle to 20 mph, and Class 3 is pedal assist to 28 mph, with a throttle not allowed in most states. The federal consumer-product definition of a low-speed electric bicycle, 15 U.S.C. § 2085, requires a motor of less than 750 W and a motor-only top speed under 20 mph.

The Thunder Pro fails on both counts, and either one is enough. Jasion's product page rates the motor at 1200 W sustained, and BikeRide reports Jasion confirmed 1,200 W nominal in writing. BikeRide also GPS-verified 35 mph on the twist throttle alone. The Jasion app, per BikeRide, can set the top speed of each assist level and the overall top speed, so you can cap it at 20 mph. That fixes the speed. It does not change the motor rating, so the bike stays outside every class whatever the display says.

On public land, check before you ride. On National Forest land, e-bikes are treated as motor vehicles and are limited to routes the forest's Motor Vehicle Use Map opens to them, and a 1200 W, 35 mph machine plainly counts. If you need something you can ride on a road or path, Jasion's EB5 MAX publishes a 750 W rated motor and a 28 mph Class 3 speed, and our street-legal electric dirt bike guide covers the in-class options. The class system explainer and our state-by-state legality guide have the detail.

52 V x 20 Ah is 1,040 Wh. A realistic e-bike uses 15-30 Wh per mile, and a 96.6 lb full-suspension fat bike that can hold 35 mph lives at the top of that range or above it. The claims, checked:

• 90 miles (listing and Jasion, PAS 1 at a 9.3 mph average, 80 kg rider, flat road, 33°C): 1,040 / 90 = 11.6 Wh per mile. Possible only at that walking-plus pace on flat ground.
• 45 miles in PAS 5 (Jasion's table): 1,040 / 45 = 23.1 Wh per mile at a stated 38 mph average, which is faster than the bike's own 35 mph top speed. That row fails twice.
• 35 miles "pure dirt range" (listing, which we read as throttle only): 1,040 / 35 = 29.7 Wh per mile. This is the one claim that is arithmetically sane.

BikeRide measured it. With a 200 lb rider and gear, on a loop with about 1,256 feet of climbing, the bike went 27.70 miles at maximum assist (18.88 mph average) and 28.42 miles in PAS 3 (18.14 mph average). That is 1,040 / 27.7 = 37.5 Wh per mile, which BikeRide places among the five least efficient fat-tire bikes it has tested, and 32% of the 90-mile claim. BikeRide's own conclusion is that the honest range is around 30 miles for most riders. That is our planning figure too: more if you are light and ride gently on the flat, less if you hold 25 mph or more.

Charging is slow. The listing promises 15% to 80% in 5 hours; Jasion's spec list says 7-8 hours and names a 2.0 A charger. Putting back 65% of a 20 Ah pack is 13 Ah, and 13 Ah at 2 A is 6.5 hours, not 5. A full charge is 20 Ah / 2 A = 10 hours, which matches BikeRide's figure. Plan on charging overnight. Our range guide explains the Wh-per-mile method.

BikeRide's review (Scott Clough-Carroll, updated October 7, 2026) scored the Thunder Pro ST 80/100. The unit was supplied by Jasion, and BikeRide states that makers do not see reviews before publication. Its measured results, beyond the range test above:

• Top speed: 35.0 mph on GPS, stable at a sustained 35 mph. The display read about 23 mph at a true 20, a 15% overread.
• Acceleration: 0 to 20 mph in 8.0 seconds on throttle and on maximum assist, against Jasion's 5-second claim. Still tied for quickest in its group.
• Climbing: a 0.99-mile hill (6% maximum grade) in 2:03 at a 29.0 mph average, and a 0.65-mile, 226-foot climb with a 12% maximum grade in 2:00 flat. Fastest in the comparison group on both.
• Braking:21 feet from 20 mph to a stop, the longest in its comparison group (average 19.5 feet), from unbranded two-piston hydraulic calipers on 180 mm rotors.
• Pedal assist: the listing sells a "64-signal precision sensor" with "twice the precision of standard systems". BikeRide found it is a cadence sensor needing three-quarters to a full crank turn before assist arrives, against a 0.3-turn average, so it used the throttle to start on hills.
• Gearing: a Shimano Tourney 7-speed with a 48t chainring and 14-28t freewheel. Pedalling stops contributing at about 20 mph.
• Other: headlight measured at 187 lux at 15 feet against an 873 lux average; the battery gauge dropped by as much as 50% under hard load and recovered at rest; assembly took 1 hour 17 minutes; zero factory defects on its unit.

Jasion describes a hydraulic suspension fork with lockout and an upgraded rear soft-tail. BikeRide lists a 70 mm coil fork with preload and lockout and a coil rear shock with a 40 mm stroke. Its verdict: real comfort over broken pavement, boardwalks and light gravel, but the fork dives under hard braking and blows through its travel, and the rear is harsh and firm over bigger hits. Read the suspension as a comfort feature, not trail hardware. BikeRide also notes the bottom bracket sits low enough to scrape a pedal in tight turns.

The payload figure needs the most care. The listing and Jasion's page both say 500 lb. BikeRide asked Jasion support, which replied in writing that combined rider and cargo weight should stay below 270 lb with the stock suspension, that 500 lb is a static structural limit, and it suggested a stiffer rear shock for heavier loads. We list the 270 lb figure. Jasion's page also says the rear rack can carry "even an extra passenger"; at 270 lb total, two adults do not fit. Heavier riders should look at our heavy-rider guide instead.

Jasion's product page lists UL 2849 as its "Standard For Safety". UL 2849 is the system-level standard for an e-bike's electrical system (battery, charger, motor and controller together), which is a broader check than UL 2271, the battery-pack-only standard. Jasion's page names no testing lab and gives no certificate or file number. BikeRide's spec sheet records UL 2849 covering the bike, battery and charger operation, and it describes both the bike and battery as UL-certified. The Amazon listing we link does not mention UL at all. If your building or landlord requires proof of UL 2849 for indoor charging, ask Jasion for the certificate before you buy; our battery fire safety guide explains what to look for. BikeRide also records an IPX4 water rating, which means splashes, not heavy rain.

Jasion sells one frame size and claims it fits riders from 5'5" to 7'2". Its own geometry chart gives a saddle height of 35 to 39 inches from the floor, an 18.3-inch seat tube, a 48.6-inch wheelbase and 5.1 inches of ground clearance. Four inches of saddle adjustment cannot cover a 21-inch spread of rider heights. BikeRide's 6'0" tester with a 33-inch inseam needed the seatpost at full extension, and it puts the realistic range at about 5'5" to 6'1". Jasion calls the Pro a high-step frame; riders at the short end should look at the Thunder Pro ST.

Weight is the ownership cost. Jasion lists 96.6 lb and BikeRide's scale read 98 lb with the accessories fitted, which BikeRide says is too heavy for most e-bike car racks. The bike ships with fenders, a rear rack, a headlight, a brake light, turn signals and a horn, and this Amazon listing adds mirrors and a rack tail bag. The 26 x 4 tires are puncture-resistant Chaoyangs per BikeRide. On cover, the listing describes a 24-month protection plan for the motor, battery and controller, while Jasion's own page and FAQ state a one-year warranty, with an extra year offered as a limited-time gift on its store. Confirm in writing which applies to an Amazon order before you rely on the second year.

If you want the same power class from other brands, the ASKGO Dirt 5500 and the Gamvire dual-motor are also off-road machines sold on bicycle listings, and our fastest e-bikes on Amazon guide ranks them.