Electric Bike Drivetrain and Gear Choices

When building or buying an electric bike, one of the most crucial decisions is selecting the right drivetrain and gear system. This choice significantly impacts your e-bike's performance, efficiency, and overall riding experience. Let's dive deep into the world of e-bike drivetrains to help you make an informed decision that perfectly matches your riding style and needs.

What Is an E-Bike Drivetrain

The drivetrain transfers power from both the rider and the motor to the wheels, directly affecting how the bike performs across different terrains and riding conditions. A well-chosen drivetrain ensures optimal efficiency, extending battery life and enhancing your riding experience.

What Are Your Drivetrain Options

1. Single Speed Drivetrains

Single speed drivetrains offer simplicity with just one gear ratio. They're ideal for:

Flat urban environments
Riders who prefer minimal maintenance
E-bikes with powerful mid-drive or hub motors that compensate for the lack of gears

The single gear ratio means you'll rely more heavily on electric assistance when facing hills or headwinds, but the trade-off is exceptional reliability and lower maintenance costs. Like Qiolor Tiger RL is the single speed off road electric bike.

2. Derailleur Gearing Systems

Traditional derailleur systems remain the most common choice for e-bikes:

Entry Level Options (7-8 speeds)

Affordable and widely available
Sufficient for casual riders on flat terrain
Typically paired with a single front chainring for simplicity

Mid Range Options (9-10 speeds)

Better shifting quality
Wider gear range
Improved durability for e-bike torque demands

Premium Options (11-12 speeds)

Extremely wide gear range
Precise shifting even under load
Specifically designed to handle e-bike torque

Derailleur systems offer excellent gear range but require regular maintenance and are more vulnerable to damage than internal hub gears.

3. Internal Hub Gears (IGH)

Internal hub gears enclose the gearing mechanism inside the rear hub:

3 Speed Hubs

Simple and reliable
Minimal maintenance
Good for flat city riding

7-8 Speed Hubs

Versatile for varied terrain
Cleaner appearance without derailleurs
Shift while stationary (ideal for urban commuting)

Premium Options (11-14 speeds)

Extremely wide gear range
Sealed from elements
Minimal maintenance requirements

Internal hub gears offer exceptional reliability and cleanliness but generally cost more and add weight to the bike. They're less prone to wear and tear, making them excellent for daily commuters and those who prefer low-maintenance solutions.

4. Belt Drive Systems

Belt drives replace the traditional chain with a carbon fiber reinforced belt:

Silent operation
No lubrication needed
Exceptionally clean (no grease)
Longer lifespan than chains (often 2-3x longer)

Belt drives typically pair with internal hub gears and require specific frame designs with a way to open the rear triangle.

How Many Gears Do You Need

The optimal number of gears depends on several factors:

For Flat Terrain/Urban Use

1-3 gears: Sufficient when your e-bike motor provides adequate assistance
7-8 gears: Offers versatility without complexity

For Mixed Terrain

9-11 gears: Provides adequate range for most hill climbs and varied conditions
Often paired with a single chainring front setup for simplicity

For Mountainous Terrain

11-12 gears or more: Offers extreme range for steep climbs
Sometimes uses a double chainring setup for maximum range

Most electric bikes have between 6 and 24 gears, with 6-9 gears being common for casual riders on flat terrain. For tackling varied terrains, including steep hills and off-road trails, having more gears (18-24) can be beneficial. However, for many users, especially those relying heavily on motor assist, 3 to 5 gears may suffice.

Some high-end systems, like the Rohloff 14-gear SPEEDHUB, offer a wide range of gearing options for refined control in a sealed, low-maintenance package.

How Gears Affect Your E-Bike's Performance

Your gear selection directly influences several crucial aspects of the riding experience:

Effects of Different Gear Ratios

Low Gear Ratios (Easier Pedaling)

Increased torque: Makes climbing hills easier with less strain
Reduced battery consumption: Less power needed from the motor when starting or climbing
Slower top speed: Limited maximum speed when pedaling in lowest gears
Improved motor efficiency: Less strain on the motor system during difficult conditions

High Gear Ratios (Harder Pedaling)

Greater top speed: Allows for faster riding on flat terrain and descents
Reduced cadence at speed: More comfortable pedaling at higher speeds
Increased battery usage: May require more motor assistance when accelerating
Reduced torque: Less effective for hill climbing without significant motor assistance

Impact on Motor Performance

For Mid-Drive Motors

The choice of gears significantly affects mid-drive motor performance:

With more gears: The motor can operate in its optimal efficiency range across various conditions
With fewer gears: The motor must work harder outside its efficiency range, potentially reducing battery life
Proper gear selection: Can extend battery range by up to 20-30% through keeping the motor in its optimal RPM range

For Hub Motors

Hub motors are less affected by gear selection but still impacted:

Direct-drive hub motors: Typically operate without multiple gears, relying on motor power alone
Geared hub motors: Can benefit from additional drivetrain gears for improved hill climbing capability
In multiple-gear systems: The motor provides consistent power regardless of gear, but rider efficiency changes

Special Electric Bike Drivetrain Needs

Several factors make e-bike drivetrains different from traditional bikes:

1. Torque Management

E-bike motors can generate significant torque, requiring:

Reinforced chains or belts
Stronger cassettes and freehubs
E-bike specific components rated for higher forces

2. Chainline Optimization

With mid-drive motors, the chainline (alignment of the chain) becomes critical:

Affects efficiency and component wear
May require specific chainring offsets
Often benefits from narrow-wide chainring designs to prevent chain drop

3. Gear Range vs. Steps

When choosing your gear system, consider:

Gear range: The difference between the highest and lowest gears (typically expressed as a percentage)
Gear steps: How close the gears are to each other

For most e-bike riders, having adequate low gears for climbing is more important than having closely spaced gears or extremely high gears for speed.

How E-Motors Change Your Gear Needs

The electrification of bikes has significantly influenced gear selection:

Reduced need for ultra-low gears: Motor assistance decreases the demand for extremely low climbing gears
Moderate gear ranges more practical: For most riders, a moderate range 7-10 speed system is usually sufficient
Simplification trend: E-bikes tend toward simpler drivetrain systems compared to traditional bikes

Best Gears for Different Types of E-Bikes

For Mountain E-Bikes

Wide range cassettes: 11-50t or 10-52t cassettes provide exceptional climbing ability
1x systems: Single front chainring with wide-range rear cassette simplifies operation while maintaining range
Motor torque considerations: Higher torque motors (80Nm+) can work effectively with fewer gears

For Commuter E-Bikes

Internal hub gears: 7-8 speed hubs offer sufficient range with minimal maintenance
Belt drive compatibility: Often paired with 5-8 internal gears for clean, reliable operation
Emphasis on reliability: Fewer, more robust components often preferred over maximum range

For Cargo E-Bikes

Ultra-low gears: Essential for starting with heavy loads
Gear inch calculation: Aim for a minimum low gear of 15-20 gear inches for loaded climbing
Component durability: Heavier-duty chains, cassettes and chainrings needed for load-bearing

Top Gear Brands for Your Budget

For Budget Builds

Shimano Tourney/Altus (7-8 speeds)
Basic single-speed setups
Entry-level internal 3-speed hubs

For Mid-Range Builds

Shimano Alivio/Deore (9-10 speeds)
SRAM X5/X7 series
Shimano Nexus 7-8 speed internal hubs

For Premium Builds

Shimano XT/XTR (11-12 speeds)
SRAM GX/X01 Eagle
Enviolo (formerly NuVinci) stepless hubs
Rohloff 14-speed internal hubs
Gates Carbon Drive belt systems

Picking the Perfect Drivetrain for Your E-Bike

When building your electric bike, the ideal drivetrain depends on your specific needs:

Consider your terrain: Hilly areas demand more gears or a more powerful motor
Evaluate your maintenance preferences: Internal hubs and belt drives offer cleanliness and reliability
Assess your budget: Higher-end components offer better performance but at increased cost
Think about integration: Ensure compatibility between your motor system and drivetrain

Remember that the best drivetrain is one that complements your motor system, matches your riding style, and meets your maintenance expectations. For many e-bike builders, a quality 9-10 speed derailleur system or 7-8 speed internal hub offers the sweet spot of performance, reliability, and value.

By carefully considering these factors, you'll create an e-bike that's not just powerful, but perfectly tuned to your individual riding style and needs.

FAQs

What's better for an e-bike: derailleur gears or internal hub gears?

Derailleur systems offer wider gear ranges at lower cost but require more maintenance. Internal hub gears provide better reliability, cleanliness, and the ability to shift while stopped—ideal for urban commuting—but typically cost more and add weight.

Can I use a single-speed setup for my e-bike?

Yes, single-speed drivetrains work well for e-bikes in flat areas or with powerful motors. They offer maximum simplicity and minimal maintenance but limit versatility in varied terrain.

Are belt drives worth it for electric bikes?

Belt drives offer significant advantages for e-bikes including cleanliness, silence, and 2-3 times longer lifespan than chains. They work best with internal hub gears and require specific frame designs, but many builders find the benefits outweigh the higher initial cost.