The world of electric bikes, or e-bikes, has witnessed a remarkable surge in popularity in recent years. Many people are converting their traditional bicycles into electric-powered wonders using conversion kits. These kits typically include a hub motor, a controller, a battery, and various other components. However, one significant concern for those looking to electrify their bicycles is whether the conversion kit will fit their specific bike. In this article, we will explore the various compatibility and fitment factors you need to consider when choosing a conversion kit for your bicycle.
What is Dropout?
Before we delve into the specifics of different bicycle types and conversion kit compatibility, it's crucial to understand the concept of "dropouts." Dropouts are the parts of a bicycle frame or fork responsible for holding the wheel in place. In traditional bikes, they often take the form of an inverted 'U' shaped channel in a flat metal plate that is welded to the frame tubing.
Before you start it is important to measure the distance between these dropouts and the width of the dropout.
What are Standard Hub Spacings?
Mountain Bikes:
Front Hub = 100mm
Rear Hub(older) = 135mm
Rear Hub(new) = 142/148mm
When it comes to classic mountain bikes, you'll often find front fork dropouts spaced 100mm apart. The rear frame dropouts on the older bikes are typically spaced at 135mm while newer models have 142mm or 148mm spacing. This setup is quite common and usually accommodates most hub motors available in the market. However, in some cases, you might need to make minor modifications, such as filing the dropout slot or spreading the rear frame to ensure a proper fit.
Folding Bikes:
Front Hub = 74mm
Rear Hub = 120/ 135mm
Folding bikes are known for their compact design, and this is reflected in their hub spacing. The front fork of a folding bike is often spaced at 74mm apart and the rear hub is 135mm spaced apart, some folding bikes take it a step further with a narrower 120mm rear dropout. To accommodate these unique dimensions, special narrow folding bike motors are available, ensuring compatibility with your folding bike.
Tandem Bikes:
Front Hub = 100mm
Rear Hub = 145mm
Tandem bicycles are built for two, and they often use wider rear dropouts to handle the added weight and stress. In these cases, hub motors can still be accommodated with the use of spacers and necessary modifications. However, it's worth noting that for tandem bikes, a front hub motor is usually recommended due to the even weight distribution between the front and rear wheels, so lack of traction on front wheel is not a huge concern and regardless front hub are easier to install.
Fat Bikes:
Front Hub = 135/155mm
Rear Hub = 150/190mm
Fat tire bikes come in various frame geometries, especially as the industry experimented with fatter tires. Many earlier fat bikes used a front fork with 135mm dropout spacing and a rear hub that was 150, sometimes with an offset frame to prevent chain rub on the tire. If your fat bike falls into this category, you can use a standard rear hub motor on the front wheel, or simply add some spacers to the rear axle.
However, modern fatbike frames often have wider rear dropouts, ranging from 175mm to 190mm, and front forks that use a 150mm front hub. Fat Bikes usually require a specially designed Fat motor.
Road Bikes:
Front Hub = 100mm
Rear Hub = 130mm
Old road bikes typically have a 100mm front fork spacing and a slightly narrower 130mm rear spacing. In most cases, you can fit both front and rear hub motors with some frame spreading. However, road bikes with drop-bar handlebars may present additional challenges when it comes to mounting components like throttles and ebrake levers. Special solutions, such as handlebob posts, can help accommodate these components.
Thru-Axle Bikes:
Thru-axle frames, once limited to high-end downhill mountain bikes, have become more common across various bike types. These frames come in different sizes, including 12mmx100 for road bikes, 15mm x 100 or 15mm x 110 boost for cross-country, gravel, and mountain bikes, and 20mm x 110 for downhill bikes. To fit a hub motor in a thru-axle dropout, you'll need a hub motor designed specifically for thru-axles, or you can use adapters available for different thru-axle sizes.
Tadpole/Recumbent Trikes:
Tadpole tricycles, with two front wheels and one rear wheel, are often electrified with a single rear hub motor. You may also use dual motor setup in front wheels but that increase the complexity and cost of the project.
Delta Trikes:
Delta trikes have one front wheel and two rear wheels, with the rider typically in an upright position. These trikes often have a basket or cargo hold in the back, with the pedals driving a shaft that turns the right rear wheel while the left rear wheel freewheels. For delta trikes, a torquey front hub motor usually works well. In cases where extreme power is required for cargo applications, a dual motor setup with an All Axle hub motor on one of the rear wheels can be a suitable solution.
Belt Drive Bikes:
Bikes with belt drives are best equipped with front hub motors. Trying to modify the belt drive system to accommodate a rear hub motor is not recommended. Opt for a front hub motor to electrify your belt-drive bicycle.
Freewheel vs. Cassette Freehub?
Understanding the type of gear system on your bike is essential for motor compatibility. Conversion kits are available for both freewheel and cassette freehub systems. If you have a 7 or 8-speed shifter, the freewheel system should work fine. However, if you have a 9, 10, or 11-speed drivetrain and want to install a rear motor, it's strongly recommended to source a hub motor with a cassette freehub. Alternatively, you can change your gear system to use an 8-speed chain and shifter for easier setup.
What to do if the Conversion Kit doesn't fit?
Filing Dropout Slot:
If your bike has slotted dropouts, and the hub motor axle is slightly too wide to fit in the slot, don't worry. This is a common situation, and you can resolve it by using a hand file to enlarge the slot or by filing the axle flats on the motor to make them narrower. Around 20-30% of bike frames may require this type of filing for proper fitment.
Frame Spreading:
In many cases, achieving a proper fit involves spreading the frame to accommodate a wider hub axle. Almost any frame, including carbon fiber and aluminum, can be spread open by a few millimeters, usually within the elastic deformation limits of the frame material. This process is especially common for steel frames. However, if you need to spread the frame significantly, like 5mm or more, it's best to perform a cold set on steel frames, a process that's generally not suitable for frames made from other materials. Cargo bikes with rear stays bridged together are nearly impossible to spread.
Can you Do It Yourself (DIY)?
At EBIKEBC, our mission is to empower DIY enthusiasts with comprehensive guides and video instructions for the seamless installation of your conversion kits. We understand that taking on an electric bike conversion project can be both exciting and challenging, and we're here to provide you with the knowledge and resources you need to make the process as smooth as possible. Whether you're a seasoned DIYer or a novice looking to dive into the world of e-bike conversions, our step-by-step guides and instructional videos are designed to help you every step of the way, ensuring that you can enjoy the thrill of building and customizing your electric bike with confidence.
If you need help?
If you ever find yourself in need of assistance, don't hesitate to reach out to our experienced tech team. They are here to guide you through the conversion kit installation process, offering expert support and answering your questions step by step, ensuring that your e-bike project is a success. Alternatively, you can also take advantage of our service center, where our skilled technicians will handle the entire conversion for you, providing a hassle-free solution to bring your electric bike vision to life. We're committed to making your e-bike journey as accessible and convenient as possible, no matter your level of expertise or preferred approach to customization.
Choosing the right conversion kit for your bicycle is an important decision, and compatibility is a key factor. By understanding your bike's dropout type, spacing, and other specific features, you can select a conversion kit that fits your bike perfectly. With the right knowledge and the appropriate adjustments or modifications, you can electrify your bicycle and enjoy the benefits of e-biking. Remember that it's essential to follow safety guidelines and seek professional help when necessary to ensure a secure and efficient conversion process. Happy riding!
