8 of the Best Electric Bike Conversion Kits [in 2021]

There’s no doubt that e-bikes have been a key driving force in rejuvenating the global cycling industry. This has been accelerated by recent global events, which have caused a massive surge in new e-bike sales. The appeal of converting a bike to electric is still incredibly popular for many people and sales of conversion kits are stronger than ever. In this article I’ll be looking at 10 of the best electric bike conversion kits you can buy in 2021.

Why convert a bike to electric?

There’s such a choice of new electric bikes available on the market now you may ask the question why would anyone want to convert a bike to electric? One of the great things about fitting an e-bike conversion kit is you can build a bike to suit your particular needs and customise things like battery range and motor power output.

tongsheng tsdz2 diy electric bike

A DIY e-bike can look just as good as a factory electric bike

Cost is another big factor. With decent mid-drive electric bikes now starting at nearly £2000, you can build your own e-bike with similar performance characteristics and battery range for a fraction of the price. Some of the best electric bike conversion kits currently available offer a riding experience that isn’t far removed from that of a high-end Bosch or Shimano Steps motor.

Are E-Bike conversion kits easy to fit?

Fitting an e-bike conversion kit certainly isn’t going to be everyone’s cup of tea. Converting a bike to electric can offer up certain challenges but the end result can be rewarding. It definitely helps if you’re ‘mechanically minded’ or a bit of a ‘DIY enthusiast’. I have personally converted hundreds of bikes to electric over the last 5 years and no two bikes are exactly the same. You certainly need a bit of patience and a calm demeanour!

Choose the right conversion kit for your bike

The most important thing to consider is compatibility with your chosen donor bike. Most electric bike hub motor kits are designed to be compatible with standard bikes that use common wheel sizes like 26″, 27.5″ and 700c and mid-drive e-bike kits are designed to fit the common BSA threaded bottom bracket shellBelow I have listed the main types of e-bike conversion kit you will come across if you’re new to this and you’re think of taking the plunge!

Types of E-Bike conversion Kit

I have focused on the three most popular types of conversion kit currently available – there is a fourth type which is a friction-drive system but with advances in technology these are no longer as popular as they once were.


Rear wheel electric bike conversion kits

As the name suggests a rear wheel electric conversion kit has an electric hub motor which is usually laced into a specific rim size. The beauty of this kind of kit is in its simplicity – you remove your existing rear wheel, swap over the tyre, tube, gear cassette (or freewheel) and disc rotor (if you have disc brakes fitted). Then you install the new motorised wheel, fit the ancillary components which will usually consist of a display, controller, pedal sensor, wiring loom and battery.

yose power rear hub motor

A rear hub motor electric conversion kit fitted to a hybrid bike

Fitting a rear wheel e-bike conversion kit will usually take between 2-3 hours but if you’re new to this it can take longer. There are several key factors to remember when buying one of these kits.

  1. Get the right size wheel for your bike – e.g. 26″, 27.5″ or 28″ / 700c
  2. Make sure your bike doesn’t have modern thru-axles – hub motor kits are only compatible with quick-release drop-outs.
  3. Ensure the spacing on the hub matches your bike drop-outs – this is usually 135mm at the rear (between the frame where the wheel fits).
  4. If fitting a downtube battery, make sure your frame is big enough to accommodate – if not, get a rear rack battery.

Rear hub conversion kit pros and cons

PROS:
  • Generally hub motors are cheap to buy
  • Fairly straightforward to install, even for a beginner
  • Performance will be on a par with factory produced hub motor bikes
  • Hub motors are generally very reliable and require little maintenance

CONS:
  • Not as tidy looking as a mid-drive installation
  • Lower torque output
  • Not as efficient as mid-drive motor
  • Not suitable for modern thru-axle wheel fitment


Front wheel electric bike conversion kits

A front wheel hub motor conversion kit is the same basic design as above but will be easier to fit for a novice as you don’t need to worry about changing the gear cassette or freewheel. Most front hub motors will fit standard 100mm quick release fork drop-outs and are not compatible with thru-axles.

yose power front wheel ebike conversion kit fitted to hybrid bike

A front hub motor e-bike conversion kit fitted to an old hybrid bike

Front hub motor kit pros and cons

PROS:
  • Cheap to buy
  • More easy to install than a rear hub motor
  • Less fuss if you need to repair a puncture
  • Performance is on a par with factory produced front hub motor e-bikes
  • Usually very reliable

CONS:
  • The extra weight in the front wheel can take some getting used to
  • Can loose traction easily on wet surfaces when climbing (wheel spin)
  • Not as efficient as mid-drives
  • Will not fit modern thru-axle wheel fitment


Mid-Drive electric bike conversion kits

Mid-drive electric bikes conversion kits are more expensive than hub motors but they provide a much more integrated and professional-looking finish, plus they’re more efficient and provide greater torque – which is important for climb steep hills. Because the motor is installed where the crankset would usually be, the extra weight is low and central which can beneficial for handling and make the bike feel more ‘planted’.

bafang is one of the best electric bike conversion kits for mountain bikes

A mid-drive e-bike conversion kit fitted to a mountain bike

Another benefit of a mid-drive e-bike motor, is the power is transferred from the motor via the bicycle drivetrain directly to he rear wheel (much like a motorcycle). This means the motor will always be spinning at a high, optimum rpm thanks to the bicycles gear ratios (providing the rider uses the gears correctly).

A typical mid-drive motor like the Bafang BBS02B or Tongsheng TSDZ2 installs where the bicycles bottom bracket fits – this is the bearing that the crankset is attached to. Installation requires complete removal the bottom bracket using a special tool and sliding the e-bike motor axle into the bottom bracket shell.

Fitting a mid-drive e-bike conversion kit can be more tricky than a hub motor as some bottom brackets can be particularly difficult to remove. I strongly recommended you use a long breaker bar with the correct socket attachment. You will also need a crank puller to remove the crank arm and crankset.

Mid-Drive motor kit pros and cons

PROS:
  • Better efficiency than a hub motor
  • High torque output – great for steep hills
  • Very neat and professional looking installation
  • Performance on a par with high-end electric bikes

CONS:
  • Installation can be tricky for a novice
  • More internal parts = more potential long-term reliability issues
  • More expensive than hub motors


LEGAL NOTICE: It is important you consider the electric bike laws in your country before deciding which kit to buy. The legal power limit in the UK and EU is 250w continuous power with 25km/h (15.5mph) maximum assisted speed. If you fit a kit that produces more power and speed than this you run the risk of having your e-bike confiscated and having points on your driving licence.

So what are the best electric bike conversion kits?

I have selected the best e-bike conversion kits from each category: Front hub motor kit, rear hub motor kit and mid-drive conversion kits. I have personal experience installing all the kits featured below and will only recommend products I feel offer good value for money.

Season 250w rear wheel kit – best budget option

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Set Alert for Product: Season 26 Inch E-Bike Conversion Kit 36V250W Rear Motor for Electric Bicycle Freewheel for Disc/V brake, with LED display, Twist throttle - £179.99
Last Amazon price update was: September 17, 2021 5:51 pm
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The Season 250w rear wheel electric bike conversion kit is the cheapest road legal kit currently available. It uses a very reliable internally gear rear hub motor which is laced into a 26″ wheel (also available in other wheel sizes).

This conversion kit is designed to be a quick and easy way to add electric assist to your existing bike, or you could purchase a new bike for the installation and it would still be cheaper than buying a new ‘off the peg’ e-bike.

This particular kit doesn’t come with a battery although there are other options available that come with a battery.

PROS:
  • The cheapest rear hub motor kit in this selection
  • Easy to install
  • Comes with everything you need (battery option available)
  • Surprisingly good performance from the 250w motor
  • Excellent quality for the price
  • No pedalling resistance when motor switched off
  • Legal in the UK and EU

CONS:
  • Basic LED display
  • Lots of wires to tidy up after installation

8.5Expert Score
A great value road legal electric bike conversion kit

The Season 250w rear wheel conversion kit is reliable and offers good performance for the price. This kit performs as well as any factory produced hub motor e-bike I've ridden and with the addition of a cheap 36v battery you can have your bike transformed into an e-bike for less than £350. Highly recommended for those on a budget who want to build a commuter e-bike or something for leisurely weekend rides.

Value for Money
10
Performance
6
Efficiency
8
Reliability
10
Check out all the Season e-bike conversion kits here

Yose Power 350w rear wheel e-bike conversion kit with battery🏆

I have been dealing with Yose Power since 2017 and can honestly say they are an excellent company who place a big focus on customer support. Their electric bike conversion kits are quite remarkable considering they are so cheap. When I ran my e-bike conversion business, the Yose Power kit was a firm favourite with my customers and many of these early conversions I did are still being used to this day.

Unfortunately this 350w rear hub motor kit isn’t technically legal in the UK (or EU) but it does offer the best all-round performance for the price. This would be ideal for a cheap e-MTB conversion for use on private land.

PROS:
  • Very high quality for the price
  • Easy to install
  • Comes with everything you need including a decent battery
  • Very good performance from the 350w motor
  • Totally reliable
  • Tools instructions and cable ties included in the kit
  • Very good LCD display
  • No pedalling resistance when motor switched off

CONS:
  • Unfortunately 350w exceeds the UK maximum power output

8.8Expert Score
One of the best value e-bike kits currently available

I have installed over 50 Yose Power kits over the last few years and I haven't had a single reported motor failure. This is amazing especially when you consider the very reasonable price. These e-bike conversion kits are always delivered quickly and are very well packaged. There is everything you need in this kit to turn your humble mountain bike or hybrid into a good quality electric bike. Yose Power have a very good reputation and having a toolkit, instructions and even cable ties is a nice attention to detail. The supplied display puts a lot of very expensive e-bike displays to shame as well. I can't recommend this kit enough.

Value for Money
10
Performance
7
Efficiency
8
Reliability
10
Check out all the Yose Power e-bike conversion kits here Visit ebikechoices.com for the full Yose Power Kit review

Season 48v 1000w rear hub motor e-bike conversion kit

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Last Amazon price update was: September 18, 2021 12:55 am
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The Season 48v 1000w rear hub motor offers the most bang for your buck. The powerful direct drive motor will give you hours of fun, providing you use the bike on privately owned land. Direct drive hub motors aren’t particularly efficient and they produce lower torque than their smaller geared motor counterparts, but what they lack in torque they make up for with outright speed. Great fun if you looking to build a high performance off-road e-bike on a budget.

PROS:
  • Offers the most ‘bang for your buck’
  • Easy to install
  • Comes with everything you need
  • Very fast – turns your MTB into an electric off-roader
  • Direct drive motors are incredibly reliable
  • Good quality KT-LCD3 display and controller

CONS:
  • Direct drive hub motors are very inefficient
  • Very heavy – adds significant weight to the rear end
  • Not legal road in the UK and EU
  • Low torque output

7Expert Score
Lots of power but heavy and inefficient

If it's speed you want then the Season 48v 1000w rear hub motor is just the ticket. My personal view of big direct drive hub motors is they are antiquated, but for sheer performance for your money, you won't get anything cheaper. The low torque motor won't be so good for climbing steep hills and will deplete your battery much faster than a geared hub motor, but these motors are incredibly robust and seem to be able to handle lots of abuse.

Value for Money
9
Performance
7
Efficiency
3
Reliability
9
These motors produce peak power well in excess of 1000w and should definitely only be used on private land. When fitting to an off-road bike you should make sure the brakes are up to the job of stopping and always wear protective clothing and helmet
Check out all the Season e-bike conversion kits here

Yose Power 250w 26″ front wheel electric bike conversion kit with battery🏆

90 %
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Set Alert for Product: YOSE POWER Hub Motor 36V250W 26" Front Motor Bicycle E-Bike Hub Conversion Kit with Hailong Plus 36V 15.6Ah Battery DIY E-bike LCD Display with Front Light - £425.00
Last Amazon price update was: September 17, 2021 1:25 pm
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Having installed quite a few Yose Power front hub motor kits, I can testify to their reliability and ease of installation. The main benefit of a front motor over a rear motor is you don’t need to worry about cassette / freewheel compatibility as with a rear kit. Fitting the front wheel is easy, just remove the existing wheel, swap everything over (not forgetting the rim tape) and install the motor wheel. Performance is lively but these motors do tend to spin on steep climbs if the road surface is wet or there’s loose gravel.

PROS:
  • Great value for money
  • Easy to install
  • Comes with everything you need including a 36v 12.5Ah battery
  • Lively performance from the 250w front motor
  • Excellent quality for the price
  • Excellent LCD display
  • Legal in the UK and EU

CONS:
  • Front motor can spin on wet / loose surfaces
  • Not compatible with modern thru-axle wheel fitment

8.8Expert Score
One of the best 250w front hub motor kits on the market

I will continue to recommend the Yose Power front wheel hub motor kit. These kits continue to be incredibly popular amongst DIY e-bike enthusiasts and are perfect for commuters and leisure riders alike. The smooth 250w geared front motor wil provide more than enough assist for most riders. Front wheel kits are not particularly suitable for situations where there are steep off-road climbs involved.

Value for Money
10
Performance
7
Efficiency
8
Reliability
10
Check out all the Yose Power e-bike conversion kits here Visit ebikechoices.com for the full Yose Power Kit review

ReaseJoy 500w front hub motor conversion kit

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The ReaseJoy 500w front hub motor kit has been on the market for quite a few years and has remained virtually unchanged in that time. These kits are so cheap because they use electric motor technology which is now quite dated when compared with other kits available.

That said, there’s still a place for these budget kits and what they lack in refinement they make up for with speed. The ReaseJoy 500w motor will produce peak power close to 750w and this will translate into a fairly high top speed but poor climbing ability due to the design of the motor.

A small, road legal 250w geared hub motor will outperform one of these on a climb, but when it comes to maintaining a higher speed on flat terrain, the ReaseJoy motor will have the edge.

PROS:
  • Cheap and cheerful!
  • Easy to install
  • Comes with everything you need apart from a battery
  • Quite fast (once it gets going)

CONS:
  • Heavy motor
  • Produces noticeable drag with motor switched off
  • Inefficient
  • Not road legal in the UK due to the 500w power rating
  • Poor hill climbing performance

6.5Expert Score
Still a viable option but looking very dated now

I'm not a big fan of direct drive motors, particularly front motors like this. I have installed a few on bikes in the past and customers have always been happy with the end result. The ReaseJoy kit is cheap and does provide a good turn of speed but is heavy and inefficient. They are incredibly reliable though which is one saving grace.

Value for Money
7
Performance
6
Efficiency
3
Reliability
10
Remember to always fit a torque-arm when installing a heavy front hub motor and do not fit to a bike with carbon fibre forks.
Check out all the ReaseJoy e-bike conversion kits here

Bafang BBS02B 750w mid-drive conversion kit🏆

7.9/10 Read review
79 %
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What can I say about the Bafang BBS02B? It’s still one of the most popular retro-fit electric bike conversion kits on the planet, and with good reason. Ever since it was first released way back in 2014 it caused quite a stir within the DIY e-bike community. It wasn’t long before software developers had created user-friendly software that enable owners to re-configure the controller parameters so they could tune the motor to their needs.

Early BBS02 models were unreliable due to poor quality MOSFET’s in the controller but this problem seems to be much less of an issue these days, due to several upgrades by Bafang over the years.

As far as performance is concerned, the BBS02B is nothing short of remarkable. Producing peak power of around 1200w (48v battery) and 120-140Nm of torque, the BBS02B is only just eclipsed by it’s bigger brother the BBSHD 1000w.

PROS:
  • Amazing performance for the price
  • Good value for money
  • Very neat, professional looking installation
  • Much more reliable than it used to be
  • Good choice of smart colour displays
  • Excellent fun for off-road riding

CONS:
  • Installation can be challenging
  • Only compatible this BSA thread bottom bracket shells (68-73mm)
  • Not road legal in the UK and EU

8.1Expert Score
Buy one - you won't be disappointed!

Out of all the conversion kits I've installed over the years the Bafang BBS02B 750w has been the most popular - I reckon I've installed over 100 of these motor kits and customers love them. I have had a few reliability issues in the past but more recently this hasn't been a problem. Just remember the legality issue and use off-road only

Value for Money
8.5
Performance
9
Efficiency
8
Reliability
7
The Bafang BBS02B produces a lot of power and any bike this motor is fitted to should be treated with respect. Remember it’s not legal to use bikes fitted with these motor kits on UK roads due to the high power output.

Check out all the Bafang e-bike conversion kits hereVisit ebikechoices.com for the full Bafang BBS02B review


Tongsheng TSDZ2 250w mid-drive electric bike conversion kit

80 %
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Set Alert for Product: Europe stock Tongsheng 36V 250W/350W TSDZ2 VLCD5 XH-18 VLCD6 LCD electric bicycle central mid motor with torque sensor - $318.61
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  • $314.67 - August 21, 2021
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  • Lowest Price: $314.67 - August 21, 2021

Tongsheng have been producing the TSDZ2 for nearly as long as the Bafang mid-drive and also suffered from early reliability problems. Thankfully the latest versions of the TSDZ2 are much more reliable and out of 30 installations I’ve only had one blue nylon gear failure.

What sets the TSDZ2 apart from the Bafang is the sophisticated torque-sensing pedal assist system. This is much more like what you’d find on an expensive Bosch or Shimano Steps-powered electric bike. This measures your pedalling force and gives you assist in relation to how much effort you’re putting in. This translates into a very smooth and natural assist feel. It also means the motor is incredibly efficient.

The Tongsheng TSDZ2 is also cheaper than the Bafang, slightly smaller and over half a kilo lighter. The installation process is similar but the Tongsheng has a useful bracket which secures the motor via an 8mm bolt to the chainstay.

PROS:
  • Cheaper than the Bafang
  • Small and lightweight
  • Very neat installation
  • Torque-sensing pedal assist
  • Very efficient
  • Good performance – comparable to a Bosch Active Plus motor
  • Legal in the UK and EU (250w version only)

CONS:
  • Installation can be challenging
  • Some long-term reliability issues persist

8.5Expert Score
A torque-sensing e-bike motor for a fraction of the cost of a Bosch

I really like the Tongsheng TSDZ2 and I think it's possibly the best road legal electric bike conversion kit available. The torque-sensing assist works very well indeed and although it's not quite as refined as Bosch or Shimano motors, considering the price, the TSDZ2 is a very viable alternative to forking out £2000 on an off-the-peg mid-drive e-bike.

Value for Money
9.5
Performance
7.5
Efficiency
9
Reliability
8

Check out all the Tongsheng e-bike conversion kits hereVisit ebikechoices.com for the full Tongsheng TSDZ2 review


Bafang BBS01B 250w mid-drive electric bike conversion kit

7.9/10 Read review
79 %
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The Bafang BBS02B’s little brother is a road legal alternative that still punches well above its weight when it comes to quality and refinement. The BBS01B 250w still produces a good turn of speed and is comparable in performance to high-end e-bike motors like Bosch and Shimano. The cadence-based pedal assist has a more on/off feel to it but this can be fine-tuned with the optional USB programming lead and free open source software.

I’ve covered a lot of miles on the Bafang BBS01B in hilly Cornwall and have always found there is plenty of power on tap for a 250w motor. It’s smooth and very quiet in operation and will fit a majority of hybrid and mountain bikes as long as they have a standard BSA threaded bottom bracket.

PROS:
  • Road legal alternative to the BBS02B
  • Very smooth and quiet
  • Surprisingly good performance from the 250w motor
  • Legal in the UK and EU

CONS:
  • Can be tricky to install for the novice

8.3Expert Score
The Bafang BBS01B is a great road legal mid-drive conversion option

As with the BBS02B, I've installed loads of these motors and only ever had one or two electrical problems. Generally the Bafang BBS01B is very reliable and offers decent performance for the price. Another thing I love about this motor is how smooth and quiet it is. Definitely worth thinking about if you want to build a capable mid-drive commuter, hybrid or mountain bike.

Value for Money
8.5
Performance
7
Efficiency
8.5
Reliability
9
Check out all the Bafang e-bike conversion kits here

Conclusion

All of the e-bike conversion kits featured in this article are good in their own way. What kind of kit is going to be suitable for you, will depend on your budget, intended use and the kind of bike you will be using.

If I had to choose a personal favourite it would be the Tongsheng TSDZ2, but I prefer riding an e-bike where I get some exercise and still need to put in a bit of an effort. If I had to choose based purely on the grin factor then it would have to be the Bafang BBS02B 750w.

For the budget conscious DIY electric bike builder who is looking for a simple, reliable commuter or leisure bike then the Yose Power kits are in my opinion unbeatable.

Thanks for reading!

If in doubt ask me a question
If you need any help or advice regarding any of the e-bike conversion kits featured, please leave a comment below and I will reply within 24hrs.
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