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Choosing an e-bike is not only about looking at motor power, battery capacity or range. The way a motor delivers assistance, the type of tires, the frame design and the overall riding setup can all change how a bike feels on the road.
The new HITWAY U Series and S Series are built around two different riding concepts. U stands for Urban, reflecting a focus on everyday city riding, commuting and practical versatility. S represents the high-performance side of the lineup, bringing a more performance-oriented motor system and riding setup for riders who want stronger and more responsive assistance.
The four models — BK-U2, BK-U3, BK-S2 and BK-S3 — are also intentionally paired. The BK-S2 is the high-performance counterpart to the BK-U2, while the BK-S3 corresponds to the BK-U3. This means the U and S Series are not simply two unrelated model lines, but two different approaches to the same model structure: balanced everyday riding in the U Series and higher-performance riding in the S Series.
In this guide, we'll look at how the two series differ, compare the four models at a glance, and help you find the HITWAY e-bike that best fits the way you ride.
U Series vs S Series: What's the Difference?
The biggest difference between the two HITWAY series is where the motor is located.
The U Series uses a rear-hub motor, with the motor integrated into the rear wheel. The S Series uses a mid-drive motor, with the motor positioned around the bike's crank area and delivering assistance through the drivetrain.
This difference affects more than just the location of the motor. It also changes how the bike delivers assistance and how it feels when accelerating, climbing or changing pace.
U Series: Rear-Hub Motor
The HITWAY U Series is built around a rear-hub motor platform designed for practical and versatile everyday riding.
The motor sits directly in the rear wheel, creating a straightforward power delivery system that works well for commuting, city riding and recreational journeys. Both the BK-U2 and BK-U3 combine their rear-hub motors with torque-sensing pedal assistance, allowing motor support to respond to the rider's pedaling effort.
The two U Series models then take different approaches to the overall riding setup. The BK-U2 focuses on a balanced everyday configuration with 29-inch tires, while the BK-U3 adds more motor torque, a larger battery and wider tires for riders looking for additional range and a more substantial tire setup.
S Series: Mid-Drive Motor
The HITWAY S Series takes a different approach with a Bafang M430 mid-drive motor.
Instead of driving the rear wheel directly from the hub, the motor works through the bike's drivetrain. Combined with torque-sensing pedal assistance, this creates a more connected riding experience that responds to how much effort the rider puts into the pedals.
The S Series is therefore particularly suited to riders who value strong motor assistance, frequent changes in elevation and a more responsive connection between pedaling and motor support.
Both the BK-S2 and BK-S3 use the same core mid-drive system, while their different frame and cockpit designs give each model its own riding character.
HITWAY U Series vs S Series: At a Glance
If you want to understand the main differences quickly, the four models can be summarized as follows:
| Feature | BK-U2 | BK-U3 | BK-S2 | BK-S3 |
|---|---|---|---|---|
| Product Image |  |
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 |
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| Motor Platform | Rear-Hub | Rear-Hub | Mid-Drive | Mid-Drive |
| Motor | 250W | 250W | Bafang M430 250W | Bafang M430 250W |
| Max. Torque | 39 Nm | 55 Nm | 120 Nm | 120 Nm |
| Sensor | Torque Sensor | Torque Sensor | Torque Sensor | Torque Sensor |
| Battery | 36V 14Ah / 504Wh | 48V 15Ah / 720Wh | 48V 15Ah / 720Wh | 48V 15Ah / 720Wh |
| Max. Range | Up to 150 km | Up to 175 km | Up to 175 km | Up to 175 km |
| Charging Time | 4.5–5 h | 4.5–5 h | 1.5–2 h | 1.5–2 h |
| Frame Type | High-Step | Low-Step | High-Step | Low-Step |
| Tire Setup | 29 × 2.25" | 27.5 × 2.8" | 27.5 × 2.2" | 27.5 × 2.2" |
| Recommended Rider Height | 160–195 cm | 165–195 cm | 160–195 cm | 165–195 cm |
| Main Character | Balanced everyday setup | More torque, range and wider tires | High-torque mid-drive setup | High-torque mid-drive with a different frame and cockpit |
The table gives you the basic picture, but the numbers alone do not tell you which model fits your riding style. For that, it helps to look at what you actually expect from your e-bike.
How Do the U and S Series Feel on the Road?
The differences between the HITWAY U Series and S Series become more noticeable once you look beyond the specifications and consider how you actually ride.
The U Series focuses on practical and versatile everyday riding, while the S Series is built around a high-torque mid-drive platform with a more responsive connection between pedaling effort and motor assistance. Within each series, tire size, battery capacity and frame design further shape the riding experience.
Here is how the two series fit different everyday riding situations.
City Commuting
For regular city commuting, both the U Series and S Series offer practical setups, but they approach everyday riding differently.
The U Series is designed around straightforward everyday usability. The BK-U2 provides a balanced configuration with a rear-hub motor and 29 × 2.25-inch tires, making it a practical choice for commuting, errands and recreational trips on everyday roads. The BK-U3 builds on this concept with more torque, a larger battery and wider 27.5 × 2.8-inch tires.
The S Series offers a more responsive mid-drive riding experience. Its torque-sensing assistance follows the rider's pedaling effort, making it suitable for riders who prefer a more connected feel between pedaling and motor support. The S2 and S3 also offer different frame and cockpit configurations, allowing riders to choose between a longer integrated setup and a shorter, wider configuration.
In short: The U Series focuses on practical everyday riding, while the S Series adds a more responsive mid-drive feel for riders who want a stronger connection with the bike.
Hilly Roads
Hilly roads make the difference between the two motor platforms more noticeable.
The S Series uses a Bafang M430 mid-drive motor with high torque output and torque-sensing assistance. Because the motor works through the bike's drivetrain and responds to the rider's pedaling effort, the S Series is particularly suited to riders who regularly encounter changes in elevation and want responsive motor assistance.
The U Series can also handle everyday inclines, with both U Series models using torque-sensing pedal assistance. The BK-U3 provides 55 Nm of torque, giving it more motor torque than the BK-U2's 39 Nm while remaining on a rear-hub platform.
In short: If hills and frequent changes in elevation are a regular part of your riding, the S Series provides a high-torque mid-drive setup, while the U3 offers a higher-torque rear-hub option within the U Series.
Long-Distance Riding
For longer rides, battery capacity and the overall riding setup become particularly important.
The BK-U2 uses a 36V 14Ah / 504Wh battery and offers up to 150 km of laboratory-tested range under suitable conditions. It is designed as a balanced option for everyday riding and longer recreational trips.
The BK-U3 steps up to a 48V 15Ah / 720Wh battery and offers up to 175 km under suitable test conditions. Its wider 27.5 × 2.8-inch tires also give the bike a more substantial setup for riders who regularly encounter less-than-perfect everyday surfaces.
The S2 and S3 both use a 48V 15Ah / 720Wh battery with a maximum tested range of up to 175 km under suitable conditions. Their Bafang M430 mid-drive systems and torque-sensing assistance are suited to riders who want a more responsive riding feel over longer journeys.
In short: The U2 provides a balanced long-range option, while the U3, S2 and S3 all step up to a 720Wh battery and up to 175 km of stated range under suitable conditions.
Mixed & Uneven Roads
When your route includes a mixture of smooth city streets, rougher surfaces and uneven sections, the tire setup and overall bike configuration become more important.
The BK-U3 stands out within the U Series with its 27.5 × 2.8-inch wider tires. Compared with the 29 × 2.25-inch tires on the U2, the wider setup gives the U3 a different character and a more substantial contact area for riders who regularly encounter less-than-perfect everyday surfaces.
The S2 and S3 use 27.5 × 2.2-inch tires and front suspension, providing a balanced setup for everyday roads and changing surfaces. Their mid-drive systems also give the S Series a more responsive character when the riding conditions or elevation change.
The U2, with its 29 × 2.25-inch tires, remains a practical all-round option for riders whose routes mainly consist of regular urban and recreational roads.
In short: Choose between the models based on the surfaces you encounter most often: the U2 offers a balanced everyday setup, the U3 adds wider tires, while the S2 and S3 combine a responsive mid-drive system with their own frame and cockpit configurations.
How to Choose the Right HITWAY E-Bike?
The right e-bike depends on more than a single specification. Think about how you normally ride, how far you travel, the roads and surfaces you encounter, and the type of riding position you prefer.
Here is how the four HITWAY models approach those different needs.
BK-U2: Balanced Everyday Riding
The BK-U2 is designed for riders who want a practical and balanced e-bike for everyday use.
Its rear-hub motor and torque-sensing pedal assistance provide straightforward support for commuting, city riding and recreational trips. The 29 × 2.25-inch tires provide a stable setup for everyday roads, while the 36V 14Ah / 504Wh battery offers up to 150 km of laboratory-tested range under suitable conditions.
The U2 is a natural fit if your priority is an uncomplicated all-round e-bike that can handle regular commuting and leisure riding without focusing on one particular type of terrain or riding style.
Explore the HITWAY BK-U2 →
BK-U3: More Power, More Range, Wider Tires
The BK-U3 is for riders who want to stay with a rear-hub motor platform but step up the overall specification.
Its 55 Nm motor provides more torque than the U2, while the 48V 15Ah / 720Wh battery increases the available battery capacity. The 27.5 × 2.8-inch wider tires also give the U3 a different character, adding a more substantial contact area for riders who regularly encounter less-than-perfect everyday surfaces.
With a maximum range of up to 175 km under suitable test conditions, the U3 is particularly relevant to riders who want more range and a wider tire setup without moving to a mid-drive system.
Explore the HITWAY BK-U3 →
BK-S2: Integrated Handlebar & Longer Frame
The BK-S2 is designed for riders who want to experience the high-torque characteristics of a mid-drive e-bike.
Its Bafang M430 mid-drive motor works with a torque sensor to provide assistance that follows the rider's pedaling effort. The 48V 15Ah / 720Wh battery supports a maximum tested range of up to 175 km under suitable conditions.
Beyond the motor and battery, the S2 has its own frame and cockpit character. Its integrated handlebar and longer, narrower frame create a different riding position from the S3.
Choose the S2 if you are interested in a mid-drive platform and prefer its integrated cockpit and longer frame configuration.
Explore the HITWAY BK-S2 →
BK-S3: Different Cockpit & Shorter, Wider Frame
The BK-S3 shares the same core mid-drive motor as the S2, including the Bafang M430 motor, torque sensor and 48V 15Ah / 720Wh battery.
The main difference is how the bike is designed around the rider. The S3 uses a separate stem and a shorter, wider frame configuration, giving it a different cockpit layout and overall riding position.
This makes the S3 a useful option for riders who want the high-torque mid-drive experience but prefer the proportions and cockpit design of a shorter, wider frame.
Explore the HITWAY BK-S3 →
Which HITWAY E-Bike Fits Your Riding Style?
If you are still deciding between the four models, it can help to start with your priorities rather than the specifications.
| If you mainly want | Consider |
|---|---|
| A balanced e-bike for everyday riding | BK-U2 |
| A rear-hub e-bike with more torque and battery capacity | BK-U3 |
| Wider tires for a more substantial everyday setup | BK-U3 |
| A high-torque mid-drive riding experience | BK-S2 or BK-S3 |
| An integrated handlebar and longer frame | BK-S2 |
| A shorter, wider frame with a separate stem | BK-S3 |
| A practical rear-hub platform | U Series |
| A mid-drive system with strong torque output | S Series |
The goal is not to find one model that suits every rider. Instead, the differences between the four bikes allow you to choose the combination of motor platform, battery capacity, tire setup and frame design that makes the most sense for your own riding.
FAQ
Can I remove the battery from a HITWAY U Series or S Series e-bike?
Yes. The batteries used on the U Series and S Series are removable, allowing you to take the battery indoors for charging rather than needing to bring the entire e-bike to a charging point.
A removable battery can also make everyday storage and charging more convenient, particularly if the bike is stored somewhere without a power outlet nearby.
How long does it take to charge a HITWAY e-bike?
Charging time depends on the model, battery condition and charger being used.
The S Series uses a 7.5A fast charger and is designed for approximately 1.5–2 hours of charging under the specified conditions. The actual charging time can vary depending on the battery's remaining charge, temperature and charging conditions.
For the U Series, charging time also varies between models because the U2 and U3 use different battery and charger configurations.
Can I use a HITWAY e-bike for long-distance riding?
Yes. The U Series and S Series are designed to support both everyday journeys and longer recreational rides.
The removable batteries, multi-speed drivetrains and suspension systems make them practical for longer rides where distance, comfort and changing road conditions all matter. The actual distance you can cover on one charge will depend on factors such as rider weight, terrain, temperature, wind, tire pressure, luggage and the level of pedal assistance being used.
For this reason, the stated maximum range should be treated as a test-condition figure rather than a guaranteed distance for every ride.
Are HITWAY e-bikes suitable for different types of terrain?
The four models are designed for more than perfectly smooth city roads, but their setups are different.
Suspension forks help absorb bumps and uneven surfaces, while the different tire configurations influence how each bike feels on the road. The U2 uses 29 × 2.25-inch tires, the U3 uses wider 27.5 × 2.8-inch tires, and the S2 and S3 use 27.5 × 2.2-inch tires.
For mixed everyday riding, the choice therefore comes down to the type of surfaces you encounter most often and the riding characteristics you prefer.
What does the torque sensor do on a HITWAY e-bike?
A torque sensor measures how much force you are applying to the pedals and uses that information to adjust motor assistance.
Instead of providing assistance based only on whether the pedals are turning, the system responds to your pedaling effort. When you pedal harder, the motor can provide more assistance; when you ease off, the assistance can reduce accordingly.
This creates a more natural connection between the rider and the motor, particularly when starting, accelerating or changing speed.
What does the IPX rating mean on a HITWAY e-bike?
An IPX rating indicates the level of protection a product has against water under defined test conditions.
For an e-bike, this is useful when considering everyday riding in conditions such as light rain or splashing. However, an IPX rating should not be interpreted as meaning that the entire bike is waterproof or that it can be submerged in water.
Always follow the specific water-resistance guidance for your HITWAY model and avoid exposing the electrical components to unnecessary water or high-pressure cleaning.