Jasion Thunder Pro

The Jasion Thunder Pro ST is a full-suspension fat-tire cruiser sold with a tantalizingly low price tag of just $1,299 (at the time of publication).

Jasion says the Thunder Pro will reach 35mph, last up to 90 miles, and “dominate streets and trails alike.” Those are bold claims for a budget e-bike, and we aim to find out if they hold up in real-world testing conditions.

Unboxing

Our Thunder Pro ST arrived without damage or missing parts, which was a relief given that plenty of online customer reports mention shipping damage and assembly issues.

The box contains tools and QR codes for downloading the user manual, app, and quickstart guide.

The bike ships mostly assembled, with just the front wheel, handlebars, pedals, and accessories left to install. We received fenders, a rear rack, mirrors, and a “tail bag.” The mirrors and tail bag are limited-time promotional gifts.

Bike Description

The steel-framed Thunder Pro is available as a step-over or step-through. Jasion claims the bike weighs 82.5lb, but I weighed it at 98lb with all of the accessories.

The frame comes in a single size, with a ridiculous height range of 5’5″ to 7’2″. At 6′ with a 33” inseam, I needed the seatpost at full extension. Riders over 6’2” probably won’t achieve full leg extension on this bike, never mind riders over 7′ tall, but more on this below.

Jasion says the Thunder Pro ST can support a 500lb payload, but their customer support told me that 500lb is a “static structural limit,” not a riding recommendation. They recommend keeping combined rider and cargo weight below 270lb with the stock suspension. That’s a huge difference.

The motor is a Jasion-branded rear hub with a 1,200W nominal power output, a 2,000W peak output, and 115Nm of torque. Again, I found conflicting numbers on Jasion’s website, so I had to ask for confirmation of these figures.

Pedal assist is managed by a cadence sensor, and the Thunder Pro has a twist throttle. A removable 52V, 20Ah or 1,040Wh battery powers the system, and both the bike and battery are UL-certified. Charging is done with a 2A charger, which takes a lengthy 10 hours to fully charge the battery.

The water resistance is just IPX4, which means the Thunder Pro shouldn’t be ridden in heavy rain. A bike marketed for “all-terrain” and “demanding conditions” should really have higher water resistance.

The Thunder Pro rolls on 26” aluminum rims and 4” Chaoyang puncture-resistant tires. The suspension includes a 70mm coil fork and a basic rear shock with a 40mm stroke. The fork has preload adjustment and lockout.

The drivetrain is a Shimano 7-speed setup with a 48t chainring and a 14-28t freewheel. Stopping is handled by generic two-piston hydraulic brakes with 180mm rotors.

The cockpit includes a seven-button keypad, thumb shifter, twist throttle, mirrors, and all the wiring, so there’s a lot going on.

The centrally mounted display is easy to read in direct sunlight, and the bike has a full safety package including front and rear lights, brake activation, turn signals, and a loud horn. There’s also app connectivity.

So, how does all of that translate out on the road?

Riding the Thunder Pro

The Thunder Pro is a massive, heavy e-bike that’s loaded with accessories, so it takes up lots of space. Again, I weighed 98lb, which also makes it one of the heaviest in this category. Thankfully, I didn’t feel the weight as much once moving.

The bike accelerates smoothly under throttle power, and the torque output is tempered, so it won’t throw you off the back. If you want a really torquey, snappy e-bike, this isn’t it, but it does reach high speeds on throttle power alone, achieving a GPS-verified 35mph.

I was surprised how composed the bike feels at that speed. The fat tires, long wheelbase, and full suspension make it feel stable feeling at these speeds. It’s worth noting that the display reads around 3mph higher than the external GPS.

The full suspension setup adds a lot of extra weight and maintenance needs, but it also provided real comfort benefits, taking the bite out of broken pavement and smoothing out light gravel paths. However, the rear shock bottoms out easily, resulting in a harsh feel over bigger hits. The budget fork also blows through its travel easily and dives under hard braking. This isn’t surprising given the price point, but it contradicts Jasion’s claim that this bike will “dominate” rough terrain.

In the stock settings, the pedal assist tuning is poor. PAS 1 pushed me to 10 or 11mph, but Level 2 took me to about 20mph, which is where ghost pedaling starts. Levels 3 to 5 all reach speeds over 20mph, and I had to spin my legs at a ridiculous cadence to contribute anything, which is something I really dislike.

The poorly tuned cadence sensor means assist takes a full pedal rotation to kick in when stopped. On a bike that weighs 100lb, this makes it difficult to get started, and impossible when on a hill. I ended up relying on the throttle to get moving first.

Thankfully, this can be fixed in the app. It allows users to adjust the top speed of every assist level, the overall top speed, and set the throttle’s output to match the chosen PAS level. With just five minutes of tinkering, I had properly tuned assist.

But there’s a quirk. When I first opened the app, the settings didn’t match how the bike behaved. I had to adjust and re-save the settings for them to sync properly. So, if the Thunder Pro isn’t responding the way it should, connect the app and re-save the adjustments.

There were two other complaints I had from testing. The first showed up during the climbing tests, where the battery gauge plummeted from full to 50 percent when under load, climbing back up after a minute of rest. These fluctuations may cause some range anxiety.

The second issue was pedal clearance. This bike sits low, and in tight, slow turns, it’s easy to scrape a pedal. I noticed it when pulling away from a stop into a sharp turn.

Pros

Power and Speed

The Thunder Pro ST delivers tons of power. I hit a GPS-verified 35mph, matching Jasion’s claim. It also posted the fastest hill climb times in its comparison group, and it holds its top speed comfortably.

Accessory Package

This bike comes with a lot of accessories and features: turn signals, a brake light, a bright headlight, a loud horn, a rear rack, fenders, and, at the time of publication, mirrors and a rack bag.

Tunability

Most bikes at this price point don’t include an app for tuning the pedal-assist levels. The Jasion app gives you control over the speed of each PAS level, overall top speed, and throttle limiting. It’s the tool that fixes the poor stock settings. Without the app, the overall pedaling experience would be pretty bad.

Cons

Every bike has its problems, and the Thunder Pro ST has a few you should know about before buying.

Payload Claim

Jasion markets a 500lb payload, but the support team told me in writing that this is a static structural limit, and that the combined rider and cargo weight shouldn’t exceed 270lb with the stock suspension. The suggested fix for heavier loads is buying a rear shock with a higher load capacity. We hope Jasion removes this from its site as this spec is misleading and shouldn’t be used to market the bike.

Height Range Claim

The claimed 5’5″ to 7’2″ height range is ridiculous. At 6′ tall, I’m using the full seatpost extension, and the long reach is sure to be a stretch for riders at the low end of that range, making the true height range much, much narrower than advertised.

Weight and Bulk

At 98lb with the accessories installed, the Thunder Pro is extremely heavy. This makes it challenging to lift and maneuver, and means it won’t fit most e-bike racks. It’s also enormous, so it requires a lot of space to store.

Test Results

Climbing Test 1 – Gradual Hill

The Thunder Pro ST really shined in our climbing tests, finishing the gradual hill in 2:03 at an average of 28.1mph; the fastest time in the comparison group, edging out the Heybike Hero’s unrestricted run by three seconds and finishing well clear of the other three.

Climbing Test 2 – Steep Hill

On the steep climb, the Thunder Pro was equally as impressive, reaching the top in two minutes at an average speed of 19.5mph. Whatever you make of Jasion’s unreliable spec sheet, the climbing power is real.

Acceleration Test

Jasion claims the bike will go from 0 to 20mph in 5 seconds, but I measured 8 seconds on both throttle and maximum pedal assist across multiple runs with a full battery. Although the claim didn’t hold, 8 seconds on throttle ties the Cobra and Obsidian for fastest in the comparison group.

Range Tests – Medium Assist, Max Assist

Jasion claims the Thunder Pro can last up to 90 miles in the lowest assist level with a 176lb rider on a flat route. Using max pedal assist with my 200lb on board, the Thunder Pro ST lasted 27.7 miles with 1,256 feet of elevation gain at a rapid 18.9mph average speed.

In its stock tune, using PAS 3, it lasted 28.4 miles at 18.1mph. These nearly identical results are because PAS 3 provides close to full power. Both results sit in the lower half of our comparison group.

Brake Test

In our brake test, the Thunder Pro ST came to a complete stop from 20mph in 21′. That’s the longest distance in the comparison group.

Conclusion

So, does the Thunder Pro ST deliver on Jasion’s promises?

Well, it depends which claim you’re looking at. It reached the claimed 35mph top speed and posted the fastest hill climbs in the comparison group, but it stops there.

The most glaring misrepresentations are the 500lb payload capacity, which is actually just 270lb as the bike is sold, and the wildly inaccurate height range. To add to that, the 90-mile range also doesn’t seem possible, even with ideal conditions, and the five-second 0 to 20mph acceleration didn’t hold up in testing.

The Thunder Pro ST is a powerful, comfortable, well-equipped cruiser with an aggressive price tag, but the budget suspension isn’t suitable for “rough terrain,” and the bike won’t “dominate” trails. Unfortunately, all of these exaggerations and misleading specs really make you doubt Jasion as a brand.

One last reminder: the 1,200W continuous power output and 35mph top speed exceed e-bike limits in most areas, so be conscious of that if want to ride this bike on public roads or trails.

Score Breakdown

• Build quality:70
• Performance/Innovation:75
• Design:70
• Ride quality:75
• Price/Value:85

Overall:75

Detailed Specs

Electric Bike Class: Unrestricted
Warranty: 1-Year limited
UL Certification: UL 2849
IP Rating: IPX4
Total Weight: Claimed: 82.5lb – As Tested: 98lb
Payload Capacity: 500lb
Motor Brand: Jasion
Motor Type: Rear hub
Motor Nominal Output: 1,200W
Motor Peak Output: 2,000W
Max Torque: 115Nm
Top Speed: 35mph
Throttle: Twist
Pedal Assist: 5 levels
Sensor: Cadence
Battery: 52V 20Ah (1,040Wh)
Charger: 2A
Charge Time: 10 hours
Range Claimed: 90 Miles
Range Tested (PAS Trail): PAS 5) 27.70 mi – 1,256 ft. – 18.88mph avg.
Display: LCD
Frame: Steel
Fork: 70mm coil suspension – preload, lockout
Brake Levers: Unbranded hydraulic
Brake Calipers: Dual-piston hydraulic
Brake Rotors: 180mm
Chainring: 48t
Derailleur: Shimano Tourney
Shifter: Shimano TX50
Freewheel: 14-28t
Rims: 26” Aluminum
Tires: 26” x 4” Chaoyang
Fenders: Full coverage
Lights: Front, rear, turn signals, brake light
Grips: Hard plastic
Saddle: Unbounded Fit
Pedals: Alloy platform
Handlebar: 700mm
Kickstand: Single-sided

Geometry Details

Frame Size 5’5” – 7’2”
Seat Tube: 18.3” (465mm)
Reach: 16.53” (420mm)
Stack: 27.16” (690mm)
Stand Over Height: 20” (508mm)
Virtual Top Tube Length: 22” (558.8mm)
Seat height minimum 35” (889mm)
Seat height max 38.5” (977.9mm)
Wheelbase: 48.6” (1234.44mm)

The Jasion Thunder Pro is definitely a decent e-bike for the price. What I like the most about this bike is the speed. This is the fastest full-size e-bike that I’ve ever reviewed on this channel.

It’s not the greatest hill climber, so that’s the biggest surprise on this thing, I think. But it’s a good-looking bike, and it’s got good, decent suspension for the money, and decent top speed overall.

The suspension and tires are doing a good job, smoothing out the bumps and cracks. So, it’s a pretty comfortable ride, although I do wish the seatpost were longer.

Is it the best bike in the world? Absolutely not. But you’ve got to look at what you’re paying for the bike, and I think for what you’re paying, it’s freaking awesome.

You have suspension in the back and suspension in the front. It’s a really feature-rich bike with a lot of great options for the price. [It’s] pretty heavy.

But the second I sat down on it, the frame basically bottomed out and was hitting the suspension that it came with.