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E-bike conversion kits offer a solution that allows you to transform your regular bike into an electric one by adding a motor, battery, and electric controls. When chosen carefully and installed correctly, these kits enable you to ride with electric assistance just like a standard e-bike. While there is now a wide range of ready-made e-bike designs available, conversion kits still have their own merits and disadvantages that need to be considered.
Advantages of E-Bike Conversion Kits
Preserve Your Beloved electric Bike : You may desire a little power boost on a beloved non-electric bike that fits you perfectly.
Unique Bikes: Electric versions may not exist for the type of bikes you prefer, such as folders and recumbents. While more options are appearing in the market, especially e-folders, electric bike conversion kits can be valuable for moderately powered bikes that closely resemble traditional bicycles. On the other hand, they can also cater to power-hungry beasts on the higher end of the spectrum.
Swapping Possibilities: E-bike conversion kits can be easily transferred between bikes, allowing you to try electric assistance on various machines. If the kit is a convenient front hub wheel kit that is easy to remove (like those offered by Leeds, Cytronex, Swytch, etc.), you can switch back to riding your bike in its original form at any time simply by reinstalling the original wheel and leaving the battery off. With such systems, you can even electrify multiple bikes by swapping the battery between them, fully utilizing its potential.
Environmentally Friendly: Opting for an e-bike conversion kit instead of buying a new e-bike is generally a greener choice, as it eliminates the need to manufacture another new bike to replace the current one you own.
Opportunity for Innovation: Bike enthusiasts who enjoy tinkering and experimenting will find the endless possibilities of motor kits and bikes intriguing. The performance of a kit depends on the bike it is installed on. Hub motors, for example, are typically designed for specific wheel sizes to comply with the speed limits set for electric bikes in their respective territories. However, you can create unique combinations by fitting a hub geared for a larger wheel into a smaller one, resulting in increased pulling power at low speeds, making it an excellent choice for climbing hills or carrying heavy loads. Additionally, you have the chance to design an e-bike that stands out from mainstream offerings. For example, Grin Technologies in Canada offers a range of solar panels and related devices that allow for solar charging of your e-bike conversion kits as you ride.
High Value: E-bike conversion kits can provide excellent value for money. If you have a bike sitting in your garage or find a good-quality bike at an affordable price, it can be converted to an e-bike at a relatively low cost compared to purchasing a new e-bike of similar quality. However, it is important to consider the quality of the recipient bike before installing a kit, as described in the Fitter’s Responsibilities section below.
Lightweight: Kits also make it possible to create an incredibly lightweight electric bike, with a total weight of 22 pounds or 10kg achievable, or even lighter if cost is not a concern. While there is now an increasing number of lightweight e-bikes available off-the-shelf, these models tend to be in the mid to high price range. Therefore, e-bike conversion kits still offer an economical pathway to owning a lightweight e-bike. There are now kits available that add just a little over 3kg to the weight of a non-electric bike, and even lighter options exist, although these may provide less power assistance.
**IMPORTANT NOTE:** Kits containing illegal motors and control units are available in the market, and many people are using them on the road, either unknowingly or intentionally. A fast and/or powerful kit can provide immense enjoyment, but it is crucial to understand that once you surpass the parameters outlined in the regulations, you are solely responsible for your actions. In most jurisdictions, your bicycle will be treated as a moped under the law and subjected to more stringent penalties associated with motorcycle use. If you are held accountable for causing harm to someone, the consequences will be severe. The electric bike legislation acts as a safety measure to protect you, and disregarding it is at your own peril.
Drawbacks of E-Bike Conversion Kits
Potential Complexity: Some e-bike conversion kits may involve a greater level of complexity compared to others, necessitating at least basic bicycle DIY skills. However, certain systems like the Leeds and Cytronex kits are relatively straightforward, requiring you to simply install a wheel, mount the battery, and attach a basic cable setup. These kits do not demand specialized knowledge about bicycles. Nonetheless, there might be instances where modifications are needed for supposedly “universal” fit systems, such as filing out narrow fork dropouts. Alternatively, all-in-one wheels like the Zehus and Smart Wheel offer convenient installation options but have their performance limitations.
Limited Choices: If you desire a mid-drive system, your options are considerably limited, and the installation process tends to be more challenging compared to most hub motor systems.
Aesthetical Concerns: Many conversion kits do not possess the polished appearance of off-the-shelf electric bikes. External cable runs secured with cable ties are commonly seen, while modern complete electric bikes tend to have concealed cables within the frame. Nevertheless, the smallest and most seamless e-bike conversion kits seamlessly integrate with the bike, making it difficult to discern that it is an electric bike.
Potential Incompatibility: It is crucial to note that not all e-bike conversion kits are compatible with all bicycles. Attention must be given to selecting the correct motor speed based on the wheel size (although most hub motors come pre-installed in the appropriate wheel size) and finding a suitable location for mounting the battery among other factors. Front hub motor conversion kits are generally easier to install compared to rear hub motor conversion kits as they do not require any interference with the gear system. Some conversion kits may need to be installed by a qualified professional, while others recommend it unless you possess extensive knowledge as a bicycle mechanic.
Varying Quality: Similar to complete electric bikes, the quality of conversion kits can vary significantly from one to another. Notably, Heinzmann stands out for their high-quality connectors and cables, instilling confidence in producing smooth and tidy cable runs, thereby minimizing the visual impact of the kit.
E-Bike Conversion Kits: Which Kit is Suitable for Me and How to Install It?
Should I opt for a geared or direct drive conversion kit system?
The majority of e-bike conversion kits utilize a geared system, where the motor power needs to be adjusted through a set of compact gears before reaching the hub shell. These kits are typically fixed-gear and geared to achieve a maximum speed of 15.5mph or 20mph (depending on whether you are purchasing a European or US spec kit). However, they can also be geared to optimize hill climbing ability, potentially resulting in a top assisted speed lower than the legal power assist limit.
Direct drive motors do not gear down onto the hub shell, so in reality the hub is the motor itself. Although this might sound ideally simple, motors generally prefer to spin at a much higher speed than the 200-400 rpm at which bike wheels typically spin. Additionally, direct drive motors lack the torque of geared motors, which is crucial for effective and efficient hill climbing abilities. To compensate for these inherent characteristics, direct drive motors are often manufactured with a wider diameter than geared motors. This helps them gain torque, but it also results in a larger size, thereby offsetting any weight savings achieved by the absence of gears.
However, direct drive motors offer distinct advantages that might be of value to you. They operate quietly, although some geared motors are now extremely quiet as well. Furthermore, direct drive motors have the capability to brake regeneratively using the motor. This feature allows you to brake during long sustained descents without having to constantly hold the brake lever. However, it is important to note that regenerative braking does not significantly recharge the battery with a meaningful amount of power.
Take into account the weight and placement of the electric bike kit
Most e-bike conversion kits weigh approximately 7 pounds or 3.2 kg for models like the Cytronex with the Nano system. On the other end of the spectrum, there are beefier motors with larger batteries that can weigh up to 20 pounds or 9 kg. It is worth noting that if the kit is excessively heavy, it may exceed the recommended weight limit for the bike, especially when considering the weight of the rider and any luggage being carried. Additionally, the distribution of weight is important as too much weight in the wrong areas can affect the bike’s handling. This particularly applies to the placement of the battery. Attaching a heavy battery to the handlebars is not advisable as it can negatively impact bike handling. Even integrating the battery into the rear rack can noticeably affect handling.
Ideally, the battery should be positioned as low down and centrally on the bike as possible. Consider if it is feasible to mount the battery on the downtube of the recipient bike. If that is not an option, attaching a bikepacking style frame bag along the top tube can be a reasonable compromise, as long as the battery is not excessively heavy.
This can vary significantly between e-bike conversion kits and different bike models. Below is a non-exhaustive list of factors that should be taken into consideration. It is important to consult with the company from which you are purchasing the kit for their specific fit requirements.
E-Bike Conversion Kits: Front Hub Motors
Front hub motors are the easiest type of kit to install and pose the fewest compatibility issues with the recipient bike. There are several considerations when fitting a front hub electric bike kit:
– Is there enough space between the forks for the motor? If it is narrower than the fork dropouts, packing washers can usually be used to make it fit. However, if the motor is wider than the dropouts, it may not be possible to fit it at all. In cases where it is possible, fork-spreading might be necessary, but this should be approached with caution as it can void the fork warranty and be dangerous if done incorrectly or excessively, especially on certain fork designs. It may also be necessary to file out the slotted fork dropout, but only in small amounts as filing it too much can weaken the fork.
The Importance of Front Fork Design
The design of the front forks is of utmost importance when it comes to electric bike conversions. It is crucial that their profile allows the motor to spin freely within the hub, with ample clearance. To ensure compatibility with their kit, Cytronex actually offers a motor template that you can use to check your forks.
It is equally important to consider the width of the front fork dropouts. They should allow the axle shoulders to slide in smoothly, without any significant sideways movement. Additionally, the dropouts must have sufficient depth to snugly accommodate the non-turn (anti-torque) washers.
Another crucial aspect to consider is whether there is enough space for the battery to fit in its designated location. Cytronex provides a template specifically designed for their unique bottle battery, which allows you to determine if it fits properly.
Conversion Kits: Rear Hub Motors
When fitting a rear hub motor, it is essential to ensure that there is enough space between the dropouts. Additionally, for single speeds, the chain line should not deviate too far from its optimal alignment. The motor should also have a compatible sprocket for derailleur gearing.
It is also important to consider whether a rear hub motor will provide the desired gear ratios. In some cases, you may need to change hub gears to accommodate a derailleur system. Furthermore, you should determine whether the rear hub allows for freewheel or freehub (cassette) gearing. The former offers a smaller range of gears, while the latter can accommodate more modern rear derailleur gear systems.
Conversion Kits: Mid-drive Motors
Mid-drive kits often require a specific bottom bracket width and threading pattern. It is worth noting that newer bikes are more likely to have non-compatible bottom bracket designs, especially those that are less than ten years old. Installing mid-drives can pose compatibility challenges and often requires specialized expertise.
For more information on bottom bracket compatibility issues, check out this advice from Empowered, which addresses common issues with Bafang mid-drive kits.
Consider how anti-torque brackets or locking devices fit onto your bike and whether your frame is compatible with them.
Conversion Kits: All-In-One Wheels
All-in-one wheels, whether they are front or rear systems, face similar fitment challenges as discussed above. For more information on this topic, refer to this guide to all-in-one wheels.
The Importance of Proper Wiring
One crucial aspect to consider is the length of the wiring runs from the motor to the battery and other components of the system. It is essential that they are long enough to ensure proper connectivity. Therefore, it is advisable to inquire about the wiring during the pre-purchasing stage with the potential supplier.
On some economical kits, the controller is a separate component that needs to be housed on the bike. This adds complexity to the wiring runs and results in more exposed wires and connections that are prone to damage and failure.
The more advanced systems have the controller integrated into the battery casing.
As an additional safety measure, some systems require you to replace your brake levers with ones that cut off motor power when activated. Keep in mind that this also adds another wiring run from the brake levers to the controller.
However, some systems do not require this. For example, the Heinzmann direct drive system relies on a precise torque sensor, so the power cuts out immediately when you stop pedalling. Similarly, the unique Cytronex sensor allows the motor to be stopped in a much shorter distance than the European EN standard requires. (The standard states that brake sensors must be installed if the motor cannot be stopped within 2m of ceasing pedalling on a road surface).
Are E-bike Conversion Kits Road Legal?
It may seem obvious, but conversion kits present an opportunity to build an e-bike that may not meet the legal criteria. It is also possible to unintentionally install a kit that produces an illegal e-bike.
In the United States, state laws play a significant role in determining the legality of e-bikes and conversion kits. Many states are adopting the three-class model for e-bikes. To determine what a typical buyer should look out for to ensure their kit produces a road legal e-bike, we will stick with this model. (For an overview of state legislation, visit here, and for specific state legislation, visit here).
According to the three-class model, “legal” e-bikes (treated as regular bicycles regarding use on roads, bike paths, and lanes) fall into the first two classes. This means the kit should have an assisted speed of 20mph and a power output limit of 750W when installed on the intended bike. Pedelec or throttle-only kits are suitable for road and bike lane use and are categorized within the first two classes (note that dirt trails have their own specific regulations). The third class is limited to pedelec only with a maximum speed of 28mph and 750 watts, but these e-bikes face restrictions on certain bike and pedestrian routes. There aren’t many kits available that offer the Class 3 option.
In European Union countries and the UK, there is a simpler regulation with a maximum assist limit of 15.5mph and a power limit of 250W. However, EU rules require the pedals of the e-bike to be turning for the power to activate. This means an electronic sensing mechanism must be installed, which typically includes a bottom bracket housed torque sensor (providing the best riding experience, but also adding cost and complexity), a motion sensor (easily fitted around the bottom bracket, but offering a less refined riding experience), or a proprietary sensing system like the one designed by Cytronex for their C1 kits.
It is also important to ensure that the kit is properly fitted to a suitable bike, as you have legal responsibilities as the fitter (see The Fitter’s Responsibilities section below).
Prevent Easy Modifications of the E-bike Kit
Consider the Manufacturer’s Track Record
Responsibilities of the Fitter
Recommended E-Bike Conversion Kits
Here is a list of suggested e-bike conversion kits, based on our knowledge of reputable companies in the electric assist kit industry.
Lightweight Hub Motor Kits – Weighing around 7-9lbs / 3-4kg
These lightweight e-bike conversion kits are perfect for electrifying bikes while keeping the final weight of the converted bike as light as possible. They are particularly suitable for folding bikes that need to be lifted frequently or for those who want a lightweight e-bike that is quick and easy to ride once the motor assistance cuts out at the legal limit.
Lightweight Hub Motor Electric Bike Kits*
Naturally, these compact kits lack the sheer motor power of their larger counterparts, although riders may prefer this as it provides a more “bikelike” experience and likely results in increased physical exertion. Therefore, if you are a spirited rider seeking a nimble e-bike that offers a slight boost on steep inclines, a lightweight hub motor electric bike kit is certainly worth considering.
To maintain a low weight, these kits often come equipped with a small battery, resulting in a potentially limited range. However, some of these smaller kits demonstrate remarkable efficiency, and when ridden by reasonably fit individuals, they can achieve impressively high figures. For instance, tests conducted on the Cytronex C1 have shown it to have a comparable range to certain mid-drive systems equipped with larger batteries.
Furthermore, there is an abundance of companies based in the EU region that manufacture small e-bike hub motor kits, primarily catering to the 250W motor power and 15.5mph assist laws that are more suitable for compact models.
*Heading 3: Cytronex C1*
The Cytronex C1, developed over a span of many years in the UK, utilizes a discreet geared front hub motor and a compact battery unit encased in a bottle. Countless components of the Cytronex kit are manufactured in the UK, boasting an array of original design features, including a mount made from marine-grade stainless steel for the bottle and a minute sprocket motion sensor responsible for delivering power. With a weight ranging between 3.2-3.6kg (approximately 7-8lbs) depending on specifications, it undoubtedly stands as one of the lightest retrofit options available.
Despite its modestly-sized battery, the Cytronex C1 manages to retain its low weight while maximizing efficiency, resulting in an impressive range from such a relatively small power source. Cytronex currently holds five patents and incorporates innovative technologies such as the sprocket motion sensor, their unique bottle battery design, and the “Boost Button,” a distinctive two-way control. The kits are available in both EU and US specifications.
The year 2021 has witnessed a host of improvements that are set to enhance the Cytronex kit’s performance. It now utilizes new lithium cells in its battery packs, delivering 198Wh, a welcomed increase from the previous 180Wh. Importantly, this increase remains within the limit allowing for transportation of the product on an aircraft. Another distinctive Cytronex feature is the inclusion of two battery packs within the bottle, each with a capacity of 99Wh, just below the threshold for dangerous goods.
Moreover, the newly introduced bottle battery units boast Bluetooth capability, enabling users to conveniently monitor charging progress from their smartphones. For instance, one can now easily check the battery’s charge level while enjoying a coffee or lunch at a cafe, without physically inspecting the bike. Additionally, the exact charge level can be viewed on the phone, and power levels can be adjusted on the go.
The Boost Button has also undergone enhancements, now featuring five different colors representing five power levels, as opposed to the previous three, and allowing for seamless navigation between them by pressing either side of the Boost Button. Furthermore, both the main C1 sensor has been further refined, making it more compact and easier to install, with universal compatibility for hub gear bikes. The Brompton sensor has also undergone further improvements, simplifying its installation process even more.
Price range: Starting from £1045 as of 2021, Cytronex offers a range of complete e-bikes powered by their system, catering to various bike styles, including tandems, and featuring a Brompton-specific model that has been thoroughly reviewed.
The UK’s Swytch offers a kit that can be easily fitted to almost any bike, and it claims to be one of the simplest kits available. The kit consists of three main components:
- 1. A front hub motor pre-laced into 28″, 26″, and 16″ (Brompton) rims, which are available in stock. They also provide a custom build service for other sizes. The only wheels that are not compatible are those with thru-axles, usually found on high-end mountain bikes that are less likely to have such a kit.
- 2. Battery options include the 180Wh (‘Eco’ kit) and the 252Wh (‘Pro’ kit). Both batteries have relatively small capacities compared to other e-bikes. If you believe you can handle the extra weight, it is recommended to go for the larger pack on your handlebars, as it is the best option for most riders.
- 3. The universal pedal sensor, which has recently been redesigned, can be easily configured to fit around the pedal crank on the opposite side of the chainwheel. It consists of a circle of twelve magnets that communicate with a separate sensor attached to the bike frame using a small sticky pad. The sensor and magnet wheel can be aligned using small Allen-head bolts to ensure accurate alignment. The goal is to get the magnets to pass as close to the sensor as possible without making contact.
I have personally tested the heavier 2.1kg (252Wh capacity) ‘Pro’ battery option, and I found that this specific kit added 4.45kg / 9.8lbs to the weight of the bike.
Vekkit, a Polish company, is a relatively new player in the market. They offer a minimalist kit that can be installed in approximately 10 minutes. The kit includes a front wheel with a motor, a bag with a battery, a wireless pedal sensor, and a wireless handlebar remote.
There are limited independent reviews available, so all the details provided are based on the company’s claims. The kit is compatible with wheel sizes ranging from 16” to 29”. The total weight added to the bike is just over 3kg for the smallest battery option. Battery options include 180Wh, 187Wh, and 360Wh. They also offer options for folding bikes like Bromton and Dahon, which have very narrow front forks.
The kit is priced at approximately €730, including shipping to the UK. This price includes the smallest battery and excludes a handlebar remote (only app control). They also offer shipping to the US; however, please note that the kits are UK/EU spec and have a 15.5mph assist limit.
The Swytch and Vekkit kits are available for purchase in the US.
The Swytch and Vekkit kits are available for purchase in the UK.
This small, light geared hub motor from the UK is perfect for Brompton conversions
This small, light geared hub motor from the UK is a fantastic choice for Brompton conversions and similar projects where electric hill climbing ability is desired without adding excessive weight. Nano Electric Bikes also offers kits for Moultons, Dahons, and other bikes upon request.
The Nano System: Innovative Design for Bromptons
The Nano system revolves around a brushless 250w, 290rpm, 36v motor integrated into a Brompton front wheel. This wheel connects to a controller via a modified luggage block and luggage frame, allowing the system to become operational when the Brompton bag, containing the battery, is securely clicked into place. It’s important to note that the Nano system for Bromptons is specifically engineered to ensure that the foldability of Brompton bikes remains unaffected. The kit offers options for pedelec only as well as pedelec plus throttle, although it does not include a twist and go feature. The kit adheres to EU/UK specifications, with a maximum assisted speed of 15.5mph.
Recent Developments: Slimmer Motor for Enhanced Compatibility
Recent advancements in the Nano system include the introduction of a slimmer motor. In many cases, this motor can be effortlessly installed into the forks of most Brompton bikes without requiring any adjustments. However, if adjustments are necessary, Nano provides the required tool and comprehensive instructions. The motor itself weighs less than 2kg and boasts an exceptional free wheel, ensuring that the difference in pedaling feel is hardly noticeable when the motor is not in use.
Travel-Friendly Option: Smaller Batteries
Nano proudly advertises the fact that their option of utilizing smaller 4Ah, 36V Bosch powertool batteries makes their system one of the few that can be taken on a plane. These Bosch batteries are widely available, simplifying the process of finding replacements or spares when needed.
Price Range and Review
The price range for Nano’s electric bike conversion kits starts at £800 for the kit alone, as of 2021. For a comprehensive understanding of the Nano system, you may refer to this detailed review of the Nano system.
About ARCC: A High-Tech Approach from Cambridge, UK
ARCC, based in Cambridge, UK, similar to Nano Electric Bikes, utilizes an EU-spec front hub motor and Bosch powertool battery for their electric bike kits. However, ARCC distinguishes itself through its high-tech approach, incorporating a wireless ‘pod’ control unit. Their specialization lies in providing conversion kits for Brompton and Airnimal Joey folders, as well as the iconic UK Moulton design. The ARCC kit adds just under 4kg to the overall weight of the bike, including the battery. It’s worth mentioning that ARCC also offers pre-fitted kits for their own range of bikes.
The Innovative ARCC e2-pod: A Fusion of Functionality and Design
The ARCC e2-pod, crafted from solid-looking aluminum, not only acts as a wiring nexus but also serves as a battery mount. It securely clamps onto the head tube and communicates wirelessly with the Bluetooth controller, conveniently mounted on the handlebar. Alternatively, if preferred, the system can be controlled using an iPhone equipped with the appropriate app. The pod also integrates the cables from a bottom bracket torque sensor and brake lever sensors, seamlessly combining various components for a streamlined design.
Battery Options: Power and Flexibility
ARCC offers battery options of 144 or 216Wh Bosch power tool batteries. Additionally, for those seeking even greater power, there is an opportunity to purchase an even larger 324Wh Bosch power tool battery, although this specific battery is not directly available from ARCC. However, it can easily be obtained through DIY outlets and similar sources.
Expert Review: Moulton Option Tested
A detailed evaluation of the Moulton option offered by ARCC has been conducted by EBR. To gain insights and a comprehensive understanding of this particular option, you can refer to their in-depth review.
Price range: Starting from £1799
Mid-weight Hub Motor Kits – Approximately 9lb – 18lb / 4-8kg
Note that in the Mid-weight Kits section, certain companies like Leeds offer a relatively lighter option, but this involves the use of compact batteries. Most of their offerings weigh over 4kg. Furthermore, it’s worth noting that some of the mentioned brands have the option of bigger batteries that are slightly heavier than 6kg. However, we have categorized them as ‘Mid-weight’ since the majority of their kits fall within the 4-6kg range.
US & UK Availability
GRIN, based in Vancouver, in collaboration with MAC from China, has developed an exceptional rear hub motor that combines the efficiency of a geared motor with regenerative power. This motor is ideal for heavy cargo hauling and loaded touring, as it provides extra riding enhancement through its weight and increased regen capabilities, which also reduces wear on braking components. Previously, gearless motors were the only choice for regenerative power. GMAC is compatible with modern freehub derailleur gears, providing a wide-ranging gear range. For more technical details, refer to the Grin video below.
Weighing approximately 8lbs / 4kg, this motor is lighter than most gearless motors by around 2lbs / 1kg.
If you prefer a ready-to-use wheel with the motor and battery included, the price will likely exceed US $2000. However, this investment will grant you one of the most innovative hub motors available.
GRIN All-Axle Hub Motor
The All Axle motor is a direct-drive front hub created by Grin from Vancouver. It is designed to be universally compatible with various quick release and thru-axle front fork standards present in today’s cycling industry. This motor is also compatible with many single side mounts for trike and quad vehicles, making it one-of-a-kind in its versatility.
Heavier Hub Motor Kits – Over 13lbs / 8kg
E-Bike Kit presents a fantastic selection of 500W rated kits for both front and rear wheels. For those who prefer, they also offer motor-only options, allowing you to find your own battery source.
All kits provided by E-Bike Kit operate at 48V. They have two main kit options: the ‘Performance’ kit, featuring a geared motor, and the ‘Heavy Duty’ kit, with a direct drive system. Additionally, they offer a specialized Fat Bike kit.
Beyond these options, E-Bike Kit also caters to e-trikes, e-tandems, and a wide range of recumbent bikes, including Catrike, HP Velotechnik, Trident Stoweway, and more.
Considering weight, the lightest E-bike kit available on their website weighs only 9.5kg / 21lbs. This can be attributed to their utilization of large and powerful motors, coupled with decent-sized batteries. In fact, their kit battery choices range from 432Wh to an impressive 960Wh.
As of 2021, the price range for complete kits starts at US $1068.
Other Grin Options
Other Grin Options
It is essential to emphasize the extensive array of kits and options available from Grin. In this article, we have endeavored to cover the most practical and innovative ones. Grin is a highly capable and knowledgeable team based in Canada. They made a name for themselves with the Cycle Analyst handlebar readout, which serves as the core of many of their remarkable e-bike conversion kits. This component allows users to program and customize various performance aspects.
Grin’s website is a treasure trove of resources, particularly for unconventional or complex DIY conversion projects. They even provide options for electrifying wheelbarrows to handle heavy loads! Whether you seek a straightforward and cost-effective conversion or an electric bike kit tailored for a heavy-duty load hauler, fat bike, or recumbent bike, you can confidently turn to Grin. While not comprehensive, there is a comprehensive overview of many of Grin’s various options available here.
Falco offers an exceptional direct drive system that boasts a wireless handlebar display and utilizes advanced five-phase motor technology (most hub drives, on the other hand, utilize three phases). The motor itself weighs 11.5lbs / 5.2kg. Even when using their smallest battery option of 500Wh, the total weight of the kit is likely to exceed 13lb / 8kg. We previously reviewed a Falco kit on a longtail cargo bike, which you can read about here.
Price range: From US $1699 for complete kits as of 2021
The notion of mid-drive power and torque-sensor efficiency remains captivating when considering kit options. In fact, it offers even greater potential for saving money compared to fitting a hub drive kit, as off-the-shelf mid-drive e-bikes typically come with significantly higher price tags than their hub motor counterparts.
However, the range of bikes that a kit is likely to fit may be limited, as the bottom bracket, which the kit needs to fit into, comes in various sizes and standards. This means that a universal fitting mid-drive kit has never been produced. Additionally, mid-drive kits tend to add more weight compared to lighter hub motor kits.
However, there are still options available for those who are looking for power, efficiency, and a well-balanced e-bike conversion. These options are definitely worth considering.
US & UK Availability
Bafang Mid-drive BBS Series
The Bafang BBS mid-drive is one of the few mid-drive kits available in the market. It comes in various versions, with the 750W and 1000W versions being commonly found in the US (BBS02 and BBSHD respectively). It is widely considered to be the most easily accessible mid-drive kit on the market.
It’s important to note that Bafang mid-drive motors only fit bikes with standard JIS-BSA bottom brackets. These bottom brackets have inner diameters of approximately 33.5-35mm. In the case of bikes with larger internal frame diameters, such as those with press-fit bottom brackets, adapters would be required for the mid-drives to fit.
Another option worth considering is Tongsheng’s TSDZ2 mid-drive. Similar to the Bafang BBS system, it originates from China and is known to offer comparable performance characteristics. One advantage of the Tongsheng mid-drive is that it offers torque sensing power along with independent throttle control. It also provides options for side bottom brackets of 100mm and 120mm, as well as a choice of voltages (36, 48, and 52V). This means that it can be fitted to bikes with non-standard bottom brackets, such as fat bikes.
All-in-One Kits (Hub Wheel Systems)
‘All-in-one’ kits are quite rare due to the technical challenges involved in designing and producing them. These kits require every component of the electric bike kit to fit inside a single wheel hub. While this simplicity is attractive, it usually results in either a very heavy hub or a hub with a small battery (which is also housed in the hub). Additionally, there may be performance compromises due to the design constraints of fitting everything into a single hub.
There are a couple of notable kits in this category:
Smart Bike Wheel
This kit was recently reviewed by EBR, and it left a good impression. It is extremely compact and affordable, with a range of 23-54 miles (depending on the PAS setting) from its 313Wh battery. The internal gyroscope and tachometer in the hub do an excellent job of regulating power from the 250W motor. The accompanying app is well-designed and connects quickly with the wheel. It also provides easy access to settings that are typically harder to find in a standard e-bike display. The only downside is that the tachometer and gyroscope system, though clever, don’t deliver the same smooth ride as torque or even cadence sensing systems (although the company offers other options). The kit adds around 20lbs / 9kg and costs starting at US $495.
Zehus was possibly one of the first companies to design and manufacture an all-in-one hub. Their hub is much smaller compared to the Smart Bike Wheel mentioned above and is designed for rear wheels, accommodating only a single gear. Consequently, its applications are somewhat limited. However, many bike companies use this system to convert their own bikes, resulting in bikes with a single gear. It is particularly popular among folding bike manufacturers, with Hummingbird claiming to have made the world’s lightest folding e-bike using this hub. The Zehus all-in-one kit adds around 3kg / 6lbs 10oz to the weight of the recipient bike. Various options are available from Nfixed in the UK, with prices starting at £1390. You may also come across this system branded as the Flykly Smartwheel.
Note that some all-in-one brands mentioned on the internet no longer produce their systems, such as Superpedestrian, Electron Wheel, and Evelo’s Omniwheel. This highlights the technical challenges associated with producing such a system.
As the name suggests, friction drives use the principle of friction to transfer motor power to the front or rear wheel of the bike. This design promises an easy-to-fit and removable system that requires minimal modification of the recipient bike.
However, while friction drives have been around for quite some time, they tend to come and go quickly. This hints at the system’s inherent weakness – the friction applied to the wheel can be prone to slipping, especially in wet weather. Additionally, most of these systems work best on smoother tires.
Nevertheless, for those riding in dry weather conditions and looking for a lightweight and affordable kit, friction drives may still have a market. Here are some of the currently available models:
A Canadian-designed system that mounts over the rear wheel in a pannier-style rack. It can accommodate one or two 278Wh batteries in the rear rack. Claimed to weigh around 13lb / 5.8kg. Prices start from US $499.
This system attaches to either the front or rear wheel and weighs around 4.5lbs / 2kg. Prices start from US $1249.
This UK-specific system is designed to fit over the front or rear wheel. Revos claims a weight of around 2-4.5 lbs / 1-2kg, including a 200Wh battery. RRP £595.
Rubbee clamps onto the seatpost and drives onto the rear wheel. Some of its features include a modular battery system and a wireless cadence sensor. Starting weight is 6.1lbs / 2.8kg.
Velospeeder is a clever-looking German design from the company behind the super-efficient Velogical rim generator for powering LED lights. It drives onto both sides of the wheel rim, rather than onto the tire like most systems. It claims to have a self-correcting anti-slip mechanism. It adds as little as 3.7lbs / 1.7kg to the bike’s weight. Prices start from €1131.