Building Your Dream Electric Mountain Bike

Electric mountain bikes are a great way to save on fuel expenses and help the environment. Building your own electric mountain bike can be an inexpensive project if you repurpose a bike you already own or buy a second-hand one. You can then convert it using a kit that includes a throttle, speed controller, and a wheel with a hub motor. You can also build an electric mountain bike from scratch, but this requires more work and knowledge. It is important to consider the legal requirements and safety precautions when building and riding your own electric mountain bike.

Choosing the right bike frame

First, decide whether you want a hardtail or full-suspension frame. Hardtail frames are more affordable, as they don't have rear suspension. Full-suspension frames offer a more comfortable ride due to their front and rear dampening capabilities. Your choice should depend on the terrain you plan to ride on. If you'll be riding on smooth surfaces like asphalt, a hardtail frame could be sufficient. However, if you'll be riding on rough terrain with lots of bumps and loose gravel, a full-suspension frame will provide a smoother experience.

Next, consider the frame's material. Avoid using a carbon fibre frame, as it may not be strong enough to support the extra weight and handle the torque of an electric motor. Opt for a mountain bike frame with a strong, sturdy material that can withstand the additional weight and torque.

When choosing a frame, ensure it has a standard bottom bracket, as this is essential for installing the electric motor conversion kit. Additionally, consider the wheel size. The most common wheel sizes for off-the-shelf conversion kits are 26", 20", or 16". Smaller wheels accelerate faster, while larger wheels provide a smoother ride and are more efficient at cruising speed.

Another factor to consider is the compatibility of the frame with other components. Ensure that the frame you choose can accommodate the necessary hardware, such as the motor, battery, brakes, fork, and handlebars. Check that the frame is compatible with the motor and battery you plan to use, as these are crucial for your electric mountain bike's performance and speed.

Lastly, think about the cost and your budget. Building your own electric mountain bike can be more affordable than buying a pre-built one, but costs can add up quickly. Consider the price of the frame, motor, battery, and other components. If budgeting is a concern, you may want to look for second-hand or used parts, or opt for more affordable options, keeping in mind that the frame and motor are the most critical components for safety and performance.

Sourcing a conversion kit

Conversion kits are a great way to add an electric boost to your mountain bike without the price tag of a full e-bike. They are also a good option if you are unable to find an e-bike that suits your needs.

When sourcing a conversion kit, it is important to consider the type of kit you require. Mid-drive kits, for example, are mounted to the bottom bracket of your bike and are good for custom configurations. Crank-driven systems are also a good option as they are easy to determine compatibility; the only requirements are an alloy frame and a bottom bracket width of between 68 and 73mm, which is standard for all road and mountain bikes.

Another factor to consider is the battery. Some kits do not come with a battery, so you will need to source your own. When doing so, ensure that the battery voltage and output match the motor. It is also important that your charger is compatible, as charger incompatibility is a common cause of fires in electric bikes.

If you are unsure about compatibility or installation, it is recommended that you seek advice from a reputable bike shop.

Installing the electric motor

First, choose the right electric bicycle conversion kit. This kit will include essential components such as a throttle, speed controller, and a wheel with a hub motor. Ensure the wheel in the kit matches the size of the existing wheels on your mountain bike. You can purchase these kits online or from a local bike shop.

Next, prepare your mountain bike. Remove the pedals and sand the bottom bracket to ensure the electric motor fits snugly. If your bike has disc brakes, remove the retaining or cotter pin, as well as the clips or springs that hold the brake pads in place.

Now, it's time to assemble the electric motor. Firmly attach a wooden stick to the area where the footbrake was previously located. Drill a small hole for the handbrake cable to pass through. Mount a small wooden board in front of the drill's button, ensuring the hole is aligned, and secure it with a wire collector.

Finally, install the handbrake cable. Feed the cable through the hole in the wooden plate, around the button on the drill, and into the wire collector. With these steps completed, your electric mountain bike is almost ready for its first ride.

Remember to prioritize safety and always wear a helmet when riding your electric mountain bike. Enjoy your new creation and the thrill of riding on your very own electric mountain bike!

Adding a braking system

When building your own electric mountain bike, adding a braking system is a crucial step to ensure your safety and control while riding. Here's a comprehensive guide to help you through the process:

Types of Braking Systems:

Before installing the braking system, it's important to understand the different types available for electric mountain bikes:

• Rim Brakes: These are the more common type of electric bike brakes. They work by creating friction between the brake pads and the rims of the wheels. There are two subtypes: caliper brakes, which are lighter but less powerful, commonly found on road bikes; and V-brakes, which are more powerful and designed for mountain motorbikes.
• Disc Brakes: Disc brakes use a rotor mounted to the wheel hub, along with brake pads, to slow down or stop the bike. Disc brakes offer better stopping power and are less affected by wet or muddy conditions, making them a popular choice for electric mountain bikes.
• Regenerative Braking: This system converts the kinetic energy of the moving bike into electrical energy stored in the battery when you apply the brakes. It improves energy efficiency and extends the range of your electric bike.
• Anti-lock Braking System (ABS): ABS brakes prevent skidding and provide smoother braking with increased stability. This system is particularly useful for inexperienced riders or those riding in varying terrain conditions.

Installing the Braking System:

The installation process will depend on the type of braking system you choose. Here are some general steps to follow:

• Prepare the Bike: Ensure your bike is in good working condition. Check the tires, brakes, and all mechanical components. Make any necessary adjustments to accommodate the braking system, such as modifying the frame or installing specific components.
• Choose the Right System: Consider your riding style, terrain, and desired level of braking. Select a system that suits your needs, whether it's rim brakes, disc brakes, or regenerative braking.
• Gather Tools and Materials: Obtain the necessary tools, such as wrenches, pliers, and wire cutters, along with the specific components required for your chosen braking system.
• Install the Brake Levers: The brake levers activate the braking system. Connect them to the calipers using cables or a hydraulic system. Ensure the levers are within easy reach and comfortable to squeeze.
• Install the Brake Pads: Position the brake pads so they make firm contact with the wheel rim (for rim brakes) or the disc rotor (for disc brakes). Adjust them to apply the right amount of pressure when activated.
• Test and Adjust: Once installed, test the braking system thoroughly to ensure it's functioning properly. Make any necessary adjustments to the brake levers, cables, or pads to optimize performance and ensure a smooth, controlled stop.

Example: DIY Electric Mountain Bike with a Drill Motor

If you're building a DIY electric mountain bike with a drill as the motor, here's a simplified process for adding a braking system:

• Remove the pedals and footbrake from the bike.
• Sand the bottom bracket to accommodate the drill.
• Assemble a wooden stick where the footbrake was previously located.
• Drill a small hole for the handbrake cable to pass through.
• Install the handbrake cable through the hole and around the button on the drill.
• Mount a small wooden board to support the drill and secure the wire collector to the pin.

Always remember to wear a helmet and ensure your electric mountain bike complies with legal requirements and safety standards. Happy building and safe riding!

Testing and safety checks

Component Compatibility and Safety:

Before assembling your bike, ensure that all components are compatible with your frameset and suited for the intended use. Pay close attention to the brakes, shifters, front forks, derailleurs, and the electric motor. Hydraulic disc brakes, for example, are recommended for electric mountain bikes due to their superior stopping power and modulation, which is crucial for controlling the increased weight of the bike.

Electrical System Testing:

The electrical system, including the battery and motor, requires thorough testing. Check the battery's power output and range to ensure it meets your expectations and the intended use of the bike. Familiarize yourself with the safety risks associated with lithium-ion batteries, which are commonly used in e-bikes. Always use manufacturer-approved chargers and batteries to minimize safety risks.

Performance and Handling Testing:

Take your assembled bike for a test ride on various trails and terrain to evaluate its performance and handling. Assess the downhill performance, suspension, and handling to ensure they meet your expectations for an electric mountain bike. Identify any potential weaknesses or adjustments needed.

Legal Requirements:

Check the legal requirements for self-built electric bikes in your region. In the EU, for instance, the individual building the bike is considered the manufacturer and is responsible for obtaining a CE mark through the necessary testing. Ensure you understand the legal consequences and insurance implications in the event of damage or loss with your self-built electric bike.

User Testing:

Before taking your electric mountain bike out on more challenging trails, familiarize yourself with its performance and characteristics on less technical routes. Electric mountain bikes have added power, which can be surprising to new riders. Practice on easier trails will help you develop the necessary bike-handling skills to navigate more technical terrain safely.

Safety should always be a top priority when building and riding your electric mountain bike. Combined with thorough testing, this will ensure a smooth and enjoyable riding experience.

Frequently asked questions