The best electric bike conversion kits will enable you to add a motor to your existing bike simply and relatively cheaply – at least compared to the price of buying a whole new electric bike.
There are an increasing number of ebike conversion kits out there, and they’re getting more sophisticated and easier to install on your bike, making for a practical alternative to a new purpose-built electric bike.
An electric bike conversion kit will include the motor to drive you along and the battery to power it. It also needs to provide the apparatus to control the power output level. This usually takes the form of a bar-mounted display.
In addition, a kit will include sensors to detect how fast you’re travelling and your level of pedal input to ensure the power supplied matches your needs.
We’ve tested a few electric bike conversion kits here at BikeRadar, but there are lots more we’re yet to try. A full test of the best electric bike conversion kits is in the works – stay tuned.
If you want a more detailed explanation of the different types of kit available and things to consider when purchasing an electric bike conversion kit, then head to our explainer further down the page.
What electric bike conversion kits are available?
Swytch electric bike conversion kit
- Pros: Very compact; easy to install; variety of range options
- Cons: 100mm threaded front axle only; not compatible with thru-axles
London-based Swytch makes a conversion kit that, it says, is the lightest in the world at 3kg total weight. It can convert any bike into an ebike.
The kit includes a 40Nm brushless hub-based motor that comes pre-laced into a replacement front wheel. The lithium-ion battery pack connects to your handlebars and also acts as the system controller and LCD display.
There’s a crank-mounted cadence sensor, and that’s all you need to fit to your bike to get going.
There’s a Brompton-specific kit available too, with an adaptor for the Brompton’s front luggage mount.
Depending on the range you want, there are three sizes of battery pack available, which provide a claimed range of 35km, 50km or 100km.
Swytch has recently unveiled an even more compact kit with a pocket-sized battery that weighs just 700g and, Swytch says, gives 15km of range.
Swytch Go electric bike conversion kit
- Pros: Price; matches the speed and power of Swytch’s costlier units
- Cons: Motor is not compatible with wheels under 26in
Swytch has also recently announced its Go bike kit, which is expected to cost less than £500. The brand says this was developed in response to the cost-of-living crisis, which has seen more people trying to save money by cycling.
The Go features a power pack, motor and pedal sensor, with wires attaching the three parts. Rather than the units sitting in a proprietary handlebar mount, the Go uses a set of simpler and cheaper Velcro straps.
Despite its simpler design, Swytch promises the same ride feel as the costlier Air and Max units.
Skarper electric bike conversion kit
- Pros: Easy to fit; level of assistance is impressive
- Cons: Not cheap
First announced in June 2022, Skarper’s ebike conversion kit comprises of a proprietary disc brake rotor and chainstay-mounted motor unit.
Fitting the Skarper is straightforward – simply remove the rear wheel’s disc rotor and replace it with the Skarper equivalent. You then attach a ‘stud’ to the chainstay, which holds the unit in place, before looping a silicone-encased pedal sensor to the bike’s crank arm.
While it’s still in pre-production, the unit is expected to weigh 3.9kg, plus a 620g rotor. The 250-watt motor is claimed to produce 32Nm of torque.
Senior technical editor Warren Rossiter got a first ride on the final prototype of the system and thinks the system could play a key role in an electrified future.
Cytronex electric bike conversion kit
- Pros: Clever sensor tech; decent range
- Cons: Not much onboard info on battery level and range
Weighing between 3.2kg and 3.6kg, the Cytronex ebike conversion kit is another front-wheel conversion to house a hub motor, but in this case, the battery is designed to fit in a standard bottle cage.
We tested the kit on a Cannondale Quick hybrid and reckon that conversion takes around 30 minutes. The charge level is displayed via LEDs on the battery, which also houses the system controller. We got up to an impressive 48 miles on a charge.
We’ve also tested the kit on a Brompton P Line lightweight folder, where the total weight undercut the C Line-based Brompton Electric. Fit it to a C Line and it’s also cheaper than the Brompton Electric.
Electric bike conversion kits: different types explained
There are a number of ways to electrify your existing bike for assistance up those hills: you can fit a powered wheel, either front or rear; you can attach a drive unit to the bottom bracket; you can fit a motor above the rear wheel and drive it via friction; or, most sneakily, you can conceal a motor in the seatpost.
Many can even be fitted by a competent home mechanic if you’re feeling handy and have an afternoon spare.
So, what are your options? Let’s take a look at the different ways to convert your non-assisted bike into an electric bike.
Powered ebike wheels
Fitting a powered ebike wheel is probably the most practical option for many people.
A powered ebike wheel is built around a special hub that contains a motor. This is usually powered by a separate battery.
This sounds simple, but the main downside is that it adds rotating mass to your bike, which feels harder to accelerate than non-rotating mass.
Be wary of systems controlled by a throttle (also called ‘twist-and-go’) though. Legally, they’re classified as electric motorcycles rather than ebikes, and need to be taxed and insured. Take a look at our guide to ebike laws for more information.
Rear-mounted friction drive ebike conversion kit
Readers of a certain age may remember earlier incarnations of these in the 1980s/90s: a box that sits on your rear wheel and powers it via friction with a rubber flywheel driven by a motor.
The idea hasn’t gone away, and lives on in devices such as the Rubbee, which promises bolt-on electric assistance for nearly any bike.
Rubbee’s base model has a claimed weight of just 2.8kg, with a 16km range that can be extended up to 48km with the top-spec, 4kg version.
It works with any wheel diameter between 16in and 29in, has an integrated carrying handle and clips on and off your seatpost. Prices start from €579.
Concealed ebike conversion kit
Now we come to the low-key way to do it – hiding a motor inside your bike so no one knows it’s there.
The Vivax Assist was the best-known device for doing this, although the company has now ceased trading. It’s the system that was used by Belgian cyclocross pro Femke Van den Driessche in 2016 to power her way to victory in her home championships. She was found out at a subsequent race, got a six-year ban and quit racing.
Vivax Assist may be no more, but we reckon this idea still has legs – at least for the budding cyclocross cheat.
Mid-drive ebike conversion kit
Many commercially available ebikes are powered with motors mounted around the bottom bracket, near the pedals.
These have the advantage of placing the weight low down on the bike, making it more stable.
This isn’t just a ready-made option though – you can also buy aftermarket conversion kits with mid-drive units.
Bafang is a brand that is increasingly focusing on complete ebikes, but it also offers a mid-drive conversion kit on Amazon, as well as wheel hub motors.
Priced from £360, Bafang says the conversion is easy to install using only a few tools to remove the bottom bracket and fit the drive on the front of the down tube.
As above, be careful of throttle-controlled kits that won’t pass the UK ebike regulations and will legally be considered a moped.
You’ll find other mid-motor systems on Amazon too, such as that from TongSheng, which is claimed to fit 95 per cent of standard bike frames and be 30 per cent lighter than a Bafang unit.
It uses a torque sensor, so should fall within the ebike regulations, and is priced from around £350 – although that doesn’t include a battery.
German brand Pendix has a mid-drive system priced from €999 to €2,190 that weighs from 5.4kg for a 28km range. It replaces a BSA bottom bracket and can be fitted to folding bikes as well as a wide range of regular machines.
Folding ebike conversion kit
What can you do if you’ve got a folding bike and want to join the electric revolution?
Well there’s good news if you’ve got a Brompton – a number of ebike conversion kits are available. They generally work with a powered hub in the front wheel and a battery carried in a bag mounted on the front.
As discussed above, Swytch and Cytronex can both be used to convert a Brompton. Swytch’s Brompton kit is priced at £999, although discounts of up to 50 per cent are sometimes available on the site.
As with its other systems, there’s a front wheel hub motor, a clip-on power pack and a bottom bracket torque sensor. Quoted range is up to 50km.
Swytch will also build wheels for folders with other wheel sizes and different fork blade widths, such as Dahon’s models.
Are electric bike conversion kits legal?
Most electric bike conversion kits are legal to fit to a bike, although the precise rules differ depending on where you live.
In most of the world, the motor needs to be limited to a maximum of 250 watts of continuous power output, unless the electric bike is only used on private land.
You also need to be pedalling for the motor to work – a throttle can only operate at low speeds and assistance needs to cut out once the speed exceeds 25kph. There may be a minimum age to ride an electric bike: in the UK it’s 14.
The rules are different in the US, where higher power outputs and higher speeds are usually legal, while Australia has some variants as well, so it’s worth checking that your electric bike conversion kit is legal where you live before purchasing.
Is converting an electric bike worth it?
An electric bike conversion kit is not cheap, so you want to be sure it’s going to work for you.
You need to have a candidate bike in decent condition to justify taking the kit route.
If you’re going to have to buy a bike to fit the kit to, or going to need to make a lot of repairs to your bike to make it roadworthy, the total cost is probably going to mean it’s not a lot cheaper than buying a complete electric bike.
You need to be confident you can fit the kit yourself as well. If you’re going to have to pay a shop to fit the motor or sort things out if the conversion goes wrong, your savings over purchasing a new electric bike may dwindle quickly.
It’s also worth noting that an electric bike conversion kit may affect your bike’s handling, particularly if there’s a heavy motor and battery mounted somewhere where the bike was not designed to carry it.
Drivetrain components may not be adequately beefed up for the extra power they need to transmit and may wear or break. Factors such as torque steer may be a problem, and cabling and sensors can be unsightly.
In contrast, if you buy a complete electric bike from a reputable brand, it will have been engineered around the motor and battery, and you’ll know what the finished product looks like.
Can you convert any bike into an electric bike?
There are designs of electric bike conversion kit that will work with pretty much any type of bike. Kits are available that are engineered specifically for certain bikes, such as the folding bike conversion kits we’ve talked about above.
A design such as the Rubbee should be mountable on most bikes. However, tyre wear may be an issue with a road bike with narrower tyres, and wet-weather grip between the motor’s drive wheel and the tyre may also be a problem.
But some kits, such as those that work with a specific bottom bracket configuration, may not fit on some bikes. An unusual wheel size may also limit available options, so it’s worth checking the compatibility of your planned solution before buying.