How to Choose the Right E-Bike Conversion Motor: A B2B Guide for Fleet, Rental and Aftermarket Applications

Choosing an electric bike conversion motor is not simply about selecting 250W, 500W, or 1000W.

For aftermarket conversion projects, the right motor must match the original bicycle frame, dropout width, wheel size, battery voltage, controller, riding environment, legal requirements, and fleet operating conditions.

For fleet operators, rental companies, distributors and companies supporting discontinued e-bike brands, motor selection is even more important because a conversion kit must work with an existing bicycle fleet, not a newly designed e-bike.

This guide explains the main types of e-bike motors, their voltage and power ranges, installation methods, drive systems, sensors, wiring, wheel sizes, dropout dimensions, and the information B2B buyers should provide when requesting a motor or conversion kit quotation.

Quick Answer: For most e-bike aftermarket projects, a geared hub motor is usually the easiest solution when the priority is simple installation, compatibility and maintenance. A mid-drive motor is generally better when climbing performance, weight distribution and integration with the bicycle's drivetrain are more important.

1. What Is an E-Bike Conversion Motor?

An e-bike conversion motor is an electric motor installed on an existing bicycle to provide electric assistance or propulsion.

A typical conversion system may include:

• Motor

• Controller

• Battery

• Display

• Throttle

• Pedal Assist Sensor (PAS)

• Brake sensor or brake lever

• Wiring harness

• Charger

• Optional torque sensor

• Optional IoT or fleet-management components

For aftermarket applications, the motor is usually the most important mechanical component because it must physically fit the bicycle and provide the required level of performance.

However, motor power alone does not determine whether a conversion kit will work.

For example:

500W motor + incorrect dropout width = installation problem

750W motor + unsuitable battery voltage = electrical compatibility problem

Correct motor + wrong wheel size = incorrect bicycle geometry and speed

Correct motor + incompatible controller = system failure

Therefore, B2B motor selection should always be treated as a complete system-matching process.

2. Why Motor Selection Is Different for the E-Bike Aftermarket

For a new e-bike manufacturer, the frame can be designed around the motor.

For an aftermarket conversion project, the situation is reversed.

The bicycle already exists.

The motor must fit the existing bicycle.

This is especially important for:

• E-bike rental fleets

• Shared mobility fleets

• Delivery fleets

• Hotel and resort rental fleets

• University fleets

• Tourist rental companies

• Bicycle refurbishment companies

• Distributors supporting discontinued e-bike brands

• Large repair and service companies

A fleet operator may have hundreds or thousands of bicycles using the same frame.

In this situation, the best motor is not necessarily the most powerful motor.

The best motor is usually the one that provides the right combination of:

Compatibility + reliability + legal compliance + installation efficiency + spare-parts availability + total operating cost.

3. Common E-Bike Motor Voltages

The most common e-bike motor system voltages are:

Which voltage should you choose?

A higher voltage does not automatically mean a better motor.

For the same power:

Higher voltage → lower current requirement

For example:

• 500W ÷ 36V ≈ 13.9A

• 500W ÷ 48V ≈ 10.4A

This can help reduce current in the electrical system and may make higher-power systems easier to design.

However, the motor, controller, battery, display and other electrical components must be matched to the same system voltage.

Simple rule

36V: common for standard city and commuter e-bikes.

48V: a strong choice for many commercial, cargo, rental and performance applications.

52V: commonly used for higher-performance aftermarket systems.

60V–72V: generally more appropriate for high-power or off-road applications where local regulations permit.

4. E-Bike Motor Power: What Does 250W, 500W or 1000W Mean?

Motor power is one of the most commonly misunderstood specifications in e-bike conversion.

A motor's rated power indicates its electrical/mechanical power classification, but real-world performance also depends on:

• Motor torque

• Controller current

• Battery voltage

• Battery discharge capability

• Motor winding

• Wheel diameter

• Rider weight

• Bicycle weight

• Terrain

• Gear ratio

• Motor efficiency

• Temperature

Therefore:

A higher wattage motor does not always mean a faster or better e-bike.

For aftermarket applications, it is better to select the motor according to the vehicle, operating environment and applicable regulations.

5. Motor Power Classes and Typical Applications

These are engineering/application categories rather than universal legal classifications.

6. E-Bike Motor Regulations: Why the Market Matters

One of the first questions in an international conversion project should be:

Where will the converted bicycle be operated?

Motor power and operating speed can affect the legal classification of an electric bicycle.

European Union

For the EU category generally associated with conventional pedal-assisted cycles, Regulation (EU) No 168/2013 excludes pedal cycles from its scope when the auxiliary motor has a maximum continuous rated power of 250W or less, assistance cuts when the rider stops pedalling, and assistance is progressively reduced and finally cut off before 25 km/h.

This is why 250W / 25 km/h pedal-assist systems are especially important for many European road-use applications.

United Kingdom

UK electrically assisted pedal cycle rules also use a 250W maximum continuous rated power and 15.5 mph assistance limit for the standard EAPC framework.

United States

The United States does not have one single nationwide e-bike classification that determines every road-use requirement. State and local laws can differ.

For example, New York defines electric-assist bicycles using a three-class system and specifies a motor below 750W, with different speed and pedal/throttle requirements for Classes 1–3.

California also uses an e-bike class system, and its current rules include specific requirements for Class 3 bicycles.

Important for fleet and rental companies

Regulations can be particularly important for commercial operators.

For example, California has enacted battery-related requirements for rental electric bicycles that become operative on January 1, 2028, including testing requirements referencing standards such as UL 2849 and EN 15194.

Therefore, a B2B conversion project should not simply ask:

“How many watts do you want?”

It should ask:

“What country/state will the converted bicycles operate in, and are they for road use, private property, rental, fleet or off-road applications?”

Regulations change and can differ by jurisdiction. The applicable local requirements should always be confirmed before finalizing a conversion specification.

7. Motor Classification by Installation Position

The two major installation positions are:

1. Hub motor

2. Mid-drive motor

7.1 Hub Motor

A hub motor is installed inside the bicycle wheel hub.

It can be installed on:

• Front wheel

• Rear wheel

Advantages

• Simple installation

• Easy aftermarket conversion

• Does not require major changes to the bicycle drivetrain

• Relatively easy maintenance

• Good compatibility with many existing bicycle frames

• Suitable for large-scale fleet conversion

Disadvantages

• Adds weight to the wheel

• Wheel removal can be more complicated because of motor cables

• Less efficient than a well-designed mid-drive system in some steep/low-speed conditions

• Rear hub motors require correct dropout and freewheel/cassette compatibility

Best applications

Hub motors are particularly suitable for:

• Rental fleets

• City bikes

• Commuter bikes

• Large-scale aftermarket conversion

• Refurbishment projects

• Discontinued-brand bicycles

• Simple fleet maintenance programs

8. Front Hub Motor vs Rear Hub Motor

Front hub motor

Best when the priority is:

simple conversion + easy installation + low modification cost

Rear hub motor

Best when the priority is:

traction + higher torque + MTB/cargo/performance applications

9. Mid-Drive Motor

A mid-drive motor is installed around the bicycle's bottom bracket area.

Instead of directly turning the wheel, it drives the bicycle through the existing drivetrain.

Advantages

• Better weight distribution

• Good climbing performance

• Uses the bicycle's gears

• Efficient for hills and variable terrain

• Natural riding feeling when combined with a torque sensor

• Excellent for MTB and cargo applications

Disadvantages

• More complicated installation

• Requires bottom bracket compatibility

• Greater drivetrain wear

• Usually more expensive

• More difficult for large-scale aftermarket conversions

Best applications

Mid-drive motors are especially suitable for:

• Mountain bikes

• Cargo bikes

• Hilly cities

• Premium commuter bikes

• Performance-oriented bicycles

• Applications requiring good weight distribution

10. Hub Motor vs Mid-Drive: Which One Should a B2B Buyer Choose?

Practical B2B conclusion

For large aftermarket fleets, hub motors are often the first option to evaluate because mechanical compatibility and installation efficiency are extremely important.

For specialized applications where climbing ability and drivetrain integration are more important, mid-drive motors deserve priority.

11. Hub Motor Dropout Width: One of the Most Important Measurements

For a hub motor conversion, the dropout width must match the bicycle frame.

The dropout is the distance between the two sides of the bicycle fork or rear frame where the wheel axle is installed.

Common hub motor widths include:

These are common dimensions, not a complete list.

Typical matching

100 mm front hub motor

→ Standard city / commuter / MTB front fork

110 mm front hub motor

→ Boost-style MTB / specific modern frames

135 mm rear hub motor

→ Common traditional MTB and city bike applications

142/148 mm

→ Modern MTB platforms

170/190/197 mm+

→ Fat tire and special frames

For an aftermarket project, never select a hub motor based only on wattage. Dropout width, axle type and wheel size should be confirmed first.

12. Mid-Drive Motor Bottom Bracket Dimensions

For mid-drive motors, the important measurement is usually the bottom bracket shell width and type.

Common widths include:

• 68 mm

• 73 mm

• 83 mm

• 100 mm

• 120 mm

• Other customized dimensions

Fat bikes and special frames may use wider bottom brackets.

For B2B projects, customers should provide:

• Bottom bracket width

• Bottom bracket type

• Shell diameter

• Crank compatibility

• Frame clearance

• Existing chainring size

For a large fleet conversion, it is strongly recommended to test the motor on the actual bicycle frame before confirming mass production.

13. Hub Motor Wheel Diameter: Which Motor Fits Which Bicycle?

Wheel diameter directly affects bicycle geometry, speed and motor performance.

Common e-bike wheel sizes include:

Why does wheel size matter?

For the same motor RPM:

Smaller wheel → higher wheel torque / lower theoretical speed

Larger wheel → higher theoretical speed / lower wheel torque at the ground

Therefore, a motor designed for a 20-inch wheel should not automatically be treated as equivalent to the same motor installed in a 29-inch wheel.

14. Geared Hub Motor vs Gearless Hub Motor

Hub motors can also be classified by internal drive structure.

Geared Hub Motor

A geared hub motor uses internal reduction gears.

Advantages

• Smaller and lighter

• High starting torque

• Good hill-climbing performance

• Efficient at low-to-medium speeds

• Excellent for city bikes

Disadvantages

• Internal gears can wear

• Usually more mechanical noise

• Freewheel mechanism adds complexity

• Maximum high-speed performance may be lower

Best for

• City bikes

• Rental fleets

• Commuter bikes

• Lightweight conversion kits

• Stop-and-go urban riding

Gearless Hub Motor

A gearless motor, also called a direct-drive hub motor, connects the motor directly to the wheel.

Advantages

• Simple internal structure

• Quiet operation

• No reduction gears

• Good high-speed performance

• Strong regenerative braking potential when supported by the controller

Disadvantages

• Heavier

• Larger motor size

• Can have lower low-speed torque compared with a geared motor of similar rated power

• More weight is added to the wheel

Best for

• High-power e-bikes

• Performance bikes

• Heavy-duty applications

• Some cargo applications

• High-speed/off-road applications where legally permitted

15. Motor Control Method: Pedal Assist, Throttle or Both?

An e-bike motor can be controlled in several ways.

PAS

PAS means Pedal Assist System.

The motor provides assistance when the rider pedals.

Advantages:

• Natural for many riders

• Simple control

• Common in road-legal pedal-assist systems

Throttle

The rider controls motor output directly through a throttle.

Common types include:

• Thumb throttle

• Half-twist throttle

• Full-twist throttle

• Button/throttle combinations

For fleet and rental applications, the throttle configuration should be considered together with the applicable local regulations.

16. Cadence Sensor vs Torque Sensor

This is one of the most important differences in riding experience.

Cadence Sensor

A cadence sensor detects whether the crank is rotating.

Advantages

• Low cost

• Simple

• Easy to install

• Reliable

• Good for basic conversion kits

Disadvantages

• Less natural response

• Motor assistance can feel like an on/off system

• Does not directly measure rider effort

Best for

• Rental bikes

• Basic commuter bikes

• Cost-sensitive conversion projects

• Large fleets

Torque Sensor

A torque sensor measures how hard the rider is pressing the pedals.

Advantages

• More natural riding feel

• Better control

• Better for hills

• Better for premium bicycles

• Can improve riding efficiency

Disadvantages

• Higher cost

• More complex

• More demanding installation

• Requires compatible controller/software

Best for

• Premium e-bikes

• MTB

• Cargo bikes

• Performance applications

Simple rule

Need low cost and simple fleet maintenance? → Cadence sensor

Need natural riding experience and precise assistance? → Torque sensor

17. Motor Power Transmission: Hub Drive vs Chain Drive

Another way to classify motors is by how the motor transfers power.

Hub drive

Motor → Wheel

Advantages:

• Simple

• Few drivetrain modifications

• Excellent for conversion projects

Mid-drive / chain drive

Motor → Crank → Chain → Cassette → Wheel

Advantages:

• Uses bicycle gearing

• Excellent climbing capability

• Better integration with bicycle drivetrain

This is why a mid-drive motor can perform very well on steep terrain even when its nominal motor power is not dramatically higher.

18. Common E-Bike Motor Wiring and Connector Types

Motor compatibility is not only mechanical.

The electrical connections must also match.

A typical hub motor may include:

Motor phase wires

Usually three thick wires.

They carry high current between the controller and motor.

Hall sensor wires

Usually a group of smaller wires.

They provide rotor position information to the controller.

Motor power + Hall cable

Many hub motors combine the phase and Hall wiring into one motor cable.

Waterproof connectors

Common in:

• Rental bikes

• Outdoor bicycles

• Cargo bikes

• Commercial fleets

• High-moisture environments

Higo/Julet-type connectors

Frequently used in integrated e-bike electrical systems.

Custom connectors

Large OEM fleets may use proprietary:

• Connector types

• Pin arrangements

• Wire colors

• Communication protocols

Therefore:

The connector appearance alone is not enough to confirm compatibility.

The supplier should also confirm:

• Connector model

• Pin number

• Pin definition

• Wire sequence

• Voltage

• Current

• Communication protocol

19. Common Motor Wiring Information

For a fleet conversion project, providing the existing connector and wiring information can significantly reduce development time.

20. How to Choose a Motor for Different E-Bike Types

21. The Best Motor Is Not Always the Most Powerful Motor

For B2B aftermarket projects, motor selection should follow this order:

Step 1 — Identify the bicycle

What model and frame is being converted?

Step 2 — Check mechanical dimensions

Confirm:

• Front/rear

• Dropout width

• Axle type

• Wheel size

• Brake type

• Cassette/freewheel

• Bottom bracket for mid-drive

Step 3 — Confirm electrical system

Check:

• Battery voltage

• Battery capacity

• Controller voltage

• Controller current

• Connector

• Communication protocol

Step 4 — Define the application

Is it:

• Rental?

• Delivery?

• Commuting?

• MTB?

• Cargo?

• Tourist operation?

• Fleet refurbishment?

Step 5 — Check regulations

Confirm the target country/state and legal operating requirements.

Step 6 — Select the motor

Only after the above information is confirmed should the motor power and motor type be finalized.

22. B2B E-Bike Motor Inquiry: What Information Should You Provide?

For a small retail purchase, a customer may only ask:

“I need a 500W motor.”

For a professional B2B conversion project, this information is not enough.

A supplier should ideally receive the following information.

23. For Fleet Customers, We Recommend Providing Photos

For aftermarket projects, photographs can save a significant amount of time.

Ideally, provide:

1. Full bicycle photo

2. Front fork/dropout photo

3. Rear dropout photo

4. Existing motor photo

5. Motor connector photo

6. Controller photo

7. Battery label

8. Display photo

9. Bottom bracket photo for mid-drive conversion

10. Wheel/rim size marking

If possible, also provide the original motor model number or bicycle model number.

A supplier can then evaluate compatibility before recommending a replacement motor.

24. A Practical Motor Selection Checklist

Before ordering an e-bike conversion motor, confirm these 12 items:

1. Target market

USA, EU, UK, Australia or another market?

2. Legal power and speed

What regulations apply?

3. Motor position

Front, rear or mid-drive?

4. Motor type

Geared or gearless?

5. Voltage

24V, 36V, 48V, 52V, 60V or 72V?

6. Power

250W, 500W, 750W, 1000W or higher?

7. Wheel size

20", 24", 26", 27.5", 28", 29" etc.?

8. Dropout width

Does the motor physically fit the frame?

9. Brake and drivetrain

Disc/rim brake? Cassette/freewheel?

10. Sensor

Cadence or torque?

11. Connector and communication

Are the motor, controller and display compatible?

12. Operating environment

Rental, delivery, commercial fleet, commuting, MTB or off-road?

If these questions are answered, motor selection becomes much easier.

25. Recommended Motor Selection by B2B Application

Rental Fleet

Recommended:

Geared rear hub motor + cadence sensor + durable waterproof connectors

Why?

• Easy maintenance

• Easy replacement

• Simple operation

• Good low-speed performance

• Suitable for large-scale fleet deployment

City Commuter Fleet

Recommended:

250–500W geared hub motor

depending on the target market and applicable regulations.

Priority:

• Reliability

• Low weight

• Low maintenance

• Comfortable acceleration

Delivery Fleet

Recommended:

500–1000W high-torque hub motor or mid-drive

depending on local regulations and vehicle design.

Priority:

• Load capacity

• Frequent starts and stops

• Climbing

• Thermal performance

• Long operating hours

MTB Fleet

Recommended:

Rear hub motor or mid-drive

Priority:

• Torque

• Climbing

• Weight distribution

• Off-road durability

Cargo Bike

Recommended:

High-torque rear hub or mid-drive

Priority:

• Total vehicle weight

• Payload

• Starting torque

• Hill climbing

• Brake system

• Thermal management

Discontinued E-Bike Brand Refurbishment

Recommended:

A compatible hub motor with matching mechanical and electrical specifications

This is often more important than choosing the newest or most powerful motor.

The key question is:

Can we convert the existing fleet with minimum changes to the frame and electrical system?

26. FAQ: E-Bike Motor Selection

What is the best motor for an e-bike conversion?

There is no single best motor for every bicycle.

For many aftermarket projects, a geared hub motor is the easiest starting point because it is relatively simple to install and maintain.

For hilly, cargo or performance applications, a mid-drive motor may be more suitable.

Is a 750W motor better than a 500W motor?

Not necessarily.

A 750W motor may provide more power, but the correct choice depends on the bicycle, rider/load, battery, controller, terrain and local regulations.

Is a hub motor or mid-drive motor better?

Hub motors are generally easier for aftermarket conversion.

Mid-drive motors generally provide better drivetrain integration and climbing performance.

The right choice depends on the application.

What voltage is best for an e-bike conversion?

36V and 48V are among the most common systems.

48V is particularly common for higher-performance and commercial applications, but the correct voltage must match the battery, controller and other electrical components.

Can I install a 500W motor on any bicycle?

No.

You must check:

• Dropout width

• Axle type

• Wheel size

• Brake compatibility

• Cassette/freewheel

• Battery voltage

• Controller

• Wiring and connectors

• Local regulations

What dropout width do I need for a hub motor?

There is no universal size.

100 mm is common for front wheels, while 135 mm is common for many traditional rear bicycle applications. Modern MTB and fat-bike platforms may use wider dimensions such as 142 mm, 148 mm, 170 mm, 190 mm or 197 mm.

Always measure the actual bicycle.

Is a geared hub motor better for rental fleets?

In many cases, yes.

A geared hub motor can provide a good balance of weight, torque, efficiency, installation simplicity and maintenance requirements.

However, the final specification should be based on the actual fleet application.

What information should I send to an e-bike motor supplier?

At minimum, provide:

Bicycle model + quantity + target market + motor position + wheel size + dropout width + voltage + required power + battery specification + controller specification + connector information + application.

Photos of the bicycle, existing motor and connectors are also highly recommended.

27. Final Guide: Choose the Motor by the Bicycle, Not Just the Wattage

For aftermarket e-bike conversion, motor selection should never begin with:

“How many watts do you want?”

A better question is:

“What bicycle are you converting, where will it be used, how will it be used, and how many bicycles need to be converted?”

The correct motor should match:

Bicycle → Dimensions → Wheel → Motor → Controller → Battery → Sensor → Wiring → Regulations → Application

For individual conversions, choosing a compatible motor is important.

For a fleet of 100, 500 or 5,000 bicycles, it becomes even more important because a small compatibility problem can multiply into hundreds of installation and maintenance problems.

For this reason, professional B2B aftermarket conversion projects should evaluate the complete system before placing a bulk order.

Need Help Selecting a Motor for Your Existing E-Bike Fleet?

If you are a rental company, fleet operator, distributor, refurbishment company or aftermarket service provider, you do not necessarily need to redesign your entire bicycle.

A suitable conversion motor and electrical system may allow an existing fleet to be upgraded or refurbished.

When requesting a quotation, send us:

Bicycle model + quantity + photos + wheel size + dropout width + battery voltage + target market + application.

We can then evaluate the mechanical and electrical requirements and recommend a suitable motor and conversion system.