Defiant ST (Step-Through) by Jupiter Bike

Meet your new Jupiter Defiant ST Step-Through Folding Electric Fat Tire Bike!

Built to completely transform the way you explore, the Jupiter Defiant ST merges heavy-duty performance with smart, portable utility. Its reinforced, low-profile folding frame makes hopping on and off effortless while maintaining a rigid, rock-solid foundation that handles urban streets and rugged backcountry trails with equal poise. Whether you are flattening steep neighborhood inclines on your morning commute or tracking deep into off-road terrain on the weekend, this e-bike delivers a plush, confidence-inspiring ride that redraws the boundaries of what a compact fat-tire bike can do.

Industry-Leading Electrical Safety

• UL 2849 Certified: This is the gold standard for eBike electrical systems. It means the entire drivetrain—including the high-torque rear hub motor, display computer, and charger—has undergone rigorous testing to prevent electrical failures, ensuring complete reliability when you are miles away from home.

• UL 2271 Certified: This specifically covers the lithium-ion battery. It ensures the "heart" of your bike is protected against overcharging, short-circuiting, and impact, providing a safer charging and storage experience in your home or garage.

Meet your new ride:

30–50+ Miles of Pedal Assist Range. A premium 48V, 13.2Ah (633.6 Wh) battery with high-quality cells powers your extended adventures and long-distance treks. Think of Watt-hours as being the size of your gas tank. (The average mid-range eBike has around 500 to 650 Wh, putting the Defiant ST right in the sweet spot for maximum efficiency!)

Max Speed. The Jupiter Defiant ST is capable of hitting 28 MPH, but out of the box, it is programmed as a Class 2 e-bike. In that setting, it caps the motor assistance at 20 MPH. To get it up to 28 MPH, you just have to change the configuration in the display settings to unlock its Class 3 capabilities. (For more info on class ratings, there's a section on that below!)

Watts with the Torque? The Defiant ST is propelled by a heavy-duty hub motor that serves up 750W of sustained power (peaking at a massive 1130W) and a hill-flattening 80 Nm of torque. Combined with a geared drive system for quiet, ultra-efficient operation, this heavy-duty power configuration means you can effortlessly conquer the steepest inclines, accelerate smoothly from a dead stop, and handle rugged terrain without breaking a sweat.

Natural Control. Utilizing a highly responsive cadence-sensing system, the motor delivers power across 5 distinct levels of Pedal Assist (PAS). This maximizes battery efficiency—yielding up to 50 miles of pedal-assist range while adapting perfectly to your preferred pacing. Out of the box, the bike is programmed with a default maximum speed of 20 MPH, but it can be easily adjusted to achieve a top speed of 28 MPH. This flexibility allows you to seamlessly configure the electronics to match your local riding and trail laws, giving you the ability to switch the bike between Class II or Class III operational modes.

What Class Rating does the Defiant ST have and why should I care?

This premium eBike offers the ultimate flexibility, capable of switching between Class I, Class II, and Class III modes. While it ships as a Class II, you can easily change it through the bright, handlebar-mounted LCD control panel.

Understanding the Class Ratings: Why Versatility Matters

Class I (Pedal Assist Only, 20 MPH): The motor provides assistance only when you are pedaling and ceases to provide help once you reach 20 MPH. This mode is widely accepted on multi-use public land paths, mountain bike trails, and state parks that strictly prohibit throttles.

Class II (Throttle & Pedal Assist): This is the "out of the box" setting. The bike includes a variable-speed twist throttle that can propel you up to 20 MPH without any pedaling required, perfect for effortless cruising or getting a boost when hauling heavy gear from a standstill.

Class III (High Speed, 28 MPH): This unlocks the eBike's top speed of 28 MPH via pedal assist. It is the ideal setting for commuting on city streets or covering long distances quickly across open gravel roads and double-tracks.

Understanding local and state ebike regulations is essential because laws vary significantly regarding where different class types are permitted, and staying informed ensures you can enjoy the full range of riding freedom while remaining legally compliant and safe on every road and trail.

Battery and Charger

The Defiant ST is powered by a high-performance 48V 13.2Ah battery pack seamlessly concealed and locked directly within the frame structure. Engineered for extreme safety, reliability, and longevity, the entire battery pack is officially UL 2271 certified. To minimize your downtime between rides, the system includes a smart charger, allowing you to quickly replenish the high-capacity cells, quick-swap the battery if you want to double your range, and get back out on your next journey with minimal waiting.

Shimano 7-Speed Gears

The Defiant ST features a high-performance Shimano Altus 7-speed drivetrain engineered for smooth, precise, and reliable shifting across varied terrain. Paired perfectly with the high-torque hub motor, this gearing configuration provides a versatile mechanical range to efficiently tackle steep climbs and maintain a comfortable pedaling cadence at top speeds. The system features an authentic Shimano rear derailleur, a matching Shimano Rapid-Fire paddle shifter, and an e-bike-rated chain built to handle the intense torque output without skipping a beat.

Hydraulic Disc Brakes

The Defiant ST is equipped with a premium hydraulic disc braking system engineered for maximum stopping power and precise, modulated control. This setup pairs dual 160mm stainless steel rotors with superior heat dissipation, offering exceptional braking leverage under heavy loads or high speeds. The system features an integrated electronic power cutoff mechanism. The moment you pull the levers, power to the motor is instantly disconnected, ensuring rapid, safe, and reliable stops in any weather or trail condition.

20" x 4" Fat Tires

The Defiant ST comes factory-equipped with premium 20" x 4.0" all-terrain knobby fat tires. Engineered specifically for compact portability and high-performance stability, these tires feature an aggressive tread pattern designed to bite deep into loose terrain, snow, sand, and mud while maintaining a smooth rolling resistance on hardpacked surfaces and pavement.

Strong and Lightweight Aluminum Alloy Frame

Built to handle the demands of rugged exploration and urban commuting alike, the Defiant ST is engineered around a premium, high-strength 6061 Aluminum Alloy frame. This robust chassis features a low step-through architecture, eliminating high leg swings and making mounting or dismounting effortless for riders of all abilities. The frame provides a rock-solid, stable foundation that ensures predictable handling, heavy-duty cargo capability, and a space-saving folding mechanism for easy storage.

Suspension

The Defiant ST features an advanced "Dual Shock" full suspension system engineered to deliver top-tier comfort and stability across rugged trails and bumpy city streets alike. Up front, a high-performance front suspension fork absorbs heavy impacts from potholes, roots, and ruts, while the rear frame shock dampens jarring vibrations on the back end. Working together with its rugged 4-inch fat tires, this setup maximizes ground traction, keeps you in total control, and provides an ultra-cushioned, floating ride no matter how wild the terrain gets.

Start me Up!

The Defiant ST is ready to go with the start of a button on the control pad!

Is this a folding eBike?

Yes! The Defiant ST features a heavily reinforced folding mechanism that allows the frame and handlebars to collapse down fast into a compact footprint (approx. 38" x 22" x 28"), making it seriously portable and easy to fit inside a car trunk, closet, or RV.

Lights, Displays, and Safety Features

Engineered for both night riding and rugged trails, the Defiant ST features a fully unified safety setup to keep you protected on every ride. You'll stay completely aware of your surroundings and metrics via the high-visibility LCD smart display. Safety features include a strong, high-output 4-bulb LED headlight for low-light navigation, a frame-integrated rear tail light that doubles as an active brake light, and a loud electric horn button located right beneath the left grip.

300 Max Load Weight

The Defiant ST supports 300 pounds combining the rider and any heavy cargo, pannier bags, or gear. The bike includes a heavy-duty, MIK-compatible rear rack and full city-style mudguards out of the box to maximize your hauling capabilities with ease.

Is the Defiant ST your size?

The recommended rider height for the Defiant ST is 5'0" through 6'2". The ultra-low step-through frame ensures a highly accessible standover height, allowing for a incredibly comfortable fit and stress-free stops.

Does the Defiant ST have a sturdy kickstand?

Yes!