Electric Bike Conversion Kit Guide – What You Need to Know

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Thinking about converting your bike to electric, but don’t know where to start? In this Electric bike conversion kit guide I will examine the different ways you can add electric assist your bicycle.

If you are willing to take the plunge, converting a bicycle to electric assist can be an extremely rewarding experience. Not only that, but you can also make a substantial saving when compared to buying a factory produced e-bike.

DIY eBike vs Factory eBike

A typical entry-level mid-drive electric bike will cost in the region of £1600 ($2000). The brand new DIY mid-drive ebike below cost me less than £900 ($1160) to build (including the cost of the new donor bike).

diy electric bike

The donor bike I used in the above build is a Decathlon BTWIN Riverside 900, with a Tongsheng TSDZ2 mid-drive motor and 36v 13ah battery.

As you can see there are substantial savings to be made by converting a decent spec new bike to electric assist. If you are converting a bicycle you already own then the savings are even greater.

Let’s say you have an old Trek or Cannondale mountain bike sitting in the shed. Typically, a decent mid-drive conversion kit with battery will set you back around £600 ($780). That’s a massive saving when compared with buying a factory-built mid-drive electric bike.

decathlon e stilus 29 electric mountain bike
The Decathlon E-Stilus is great, but you won’t get much change from £3000!

Converting a bike to electric isn’t for everyone though, and if you’re not mechanically minded, I would recommend purchasing a factory-produced electric bike or find someone who can fit the kit for you.

You will also need to consider the fact that a retro-fit electric bike conversion motor may not be as reliable in the long-term as a Bosch or Shimano steps motor commonly found on factory produced electric bikes.

Useful Links

In order to choose the right motor for your needs, you need to ask yourself what your intended use is going to be.

If you live in a fairly flat area, with only slight inclines, then a small geared hub motor should be more than adequate, but if you live in an area where there are relentless steep hills, then a mid-drive would be more suitable.

Ultimately, the decision you make will be influenced by your own personal needs.  Both types of motor have their place on e-bikes but it is worth remembering that mid-drives in general are far more energy efficient than small hub motors.

Direct drive hub motors

The direct drive hub motor is the simplest form of electric bike propulsion: The outer shell of the hub is an integral part of the motor, and has a big ring of powerful magnets fixed to it.

When the motor runs, it drives the wheel directly (that’s where the name comes from). Put simply this means that the wheel is basically a motor with the shaft fixed in place so that the body of the motor (the outer hub shell, and thus your wheel) spins instead of the shaft.

direct drive hub motor installed on a hardtail mountain bike

It is a simple design, but comes at a cost – the motor needs to be quite big and heavy to produce enough power. A smaller motor spinning slowly wouldn’t produce enough torque, and the speed you want your wheel to turn at is relatively slow, so the motor needs to be as big as possible to produce torque at low speeds.

On the positive side, direct drive hub motors tend to be cheap and reliable plus they can handle a lot of power. So if you are looking for a high performance electric bike on a budget then a big hub motor may be the way to go.

Geared Hub Motor

Small geared hub motors are a lot more efficient than direct drive motors. The motor case is connected to the stator through a planetary gear reduction system. For every rotation of the case, the motor inside spins many times faster. This allows the motor to work at higher (and more efficient) speeds, while still allowing the wheel to spin at a slower driving speed.

Another great benefit to using a geared hub motor is there is practically zero pedalling resistance if the motor is switched off or runs out of power – you can pedal like on a normal bicycle.

a small geared hub motor installed on a mountain bike

Geared motors are usually maintenance-free, but if you do a lot of hill climbing it is likely the nylon planetary gears will wear over time. Thankfully these are cheap and relatively easy to replace.

Check out the best hub motor conversion kit on eBay

Front Hub motor vs Rear Hub Motor

Front wheel Electric bike conversion Kit

There are various pros and cons of fitting a front hub motor vs rear hub motor. When it comes to electric wheels, front hub motors are usually more straightforward to fit. The main reason for this is you do not need to worry about swapping over gear cassettes or freewheels.

Front wheel electric bike conversion kit fitted to a ladies hybrid bike

It should be noted, that the best option for a front wheel electric conversion would be a small, geared hub motor. The reason for this, is they are compact, lightweight and produce reasonable torque.

Larger direct drive front wheel electric bike kits are available. They are generally cheaper and more powerful, but the extra size of the motor can make it difficult to fit onto bikes that have disc brakes. They are also considerably heavier and less efficient.

bafang 250w hub motor electric bike conversion kit

Another plus with a front hub motor is when you are using the pedal assist, the bike is effectively being driven by both wheels. Whilst the electric front wheel is giving you help, you are putting power through the rear wheel by pedalling.

Electric front wheels are not particularly good for off-road riding, as the powered wheel can have a tendency to spin on rough ground, particularly when climbing steep hills.

Rear Wheel Electric Bike Conversion Kit

A rear wheel electric hub motor is usually the preferred way to add electric assist to a bicycle using a conversion kit. Changing the rear wheel involves a little more work, specifically removing the gear cassette (or freewheel), you will need a special tool for this job.

As far a riding is concerned, the motor is pushing as opposed to pulling you (as with a front motor). Generally a smaller geared rear hub motor will look a lot more discreet.

bafang 48v 500w cst rear hub motor kit with color display

Another bonus with rear hub motors, is they are a lot better for use on rough ground. All of the rider weight is concentrated on the back wheel, there is much less of a problem with wheel spin.

The only real downside with this set-up, is replacing an inner tube in the event of a puncture can be time-consuming. I always recommend a good puncture resistant tyre like a Schwalbe Marathon Plus to greatly reduce this risk.

Mid-Drive Motor

The mid-drive motor is the preferred drive system of more expensive e-bikes. These types of motors are by far the most efficient and they also produce much more torque than hub motors.

a bafang bbshd mid drive motor installed on a hybrid bike

Fitting this kind of motor can be tricky for the inexperienced, as the bicycle’s bottom bracket needs to be removed to facilitate installation. Once this job has been done, the rest is fairly straightforward. It is important to remember that most mid-drive kits are only compatible with standard threaded bottom bracket shells of 68mm-73mm wide and approximately 33.5mm diameter.

When installed correctly, a mid-drive system will give your bike the look and feel of a more expensive e-bike.

cube mountain bike with a bafang bbs02 and 52v battery

The only downsides to mid-drive motors are increased pedalling resistance when the motor is switched off and periodic maintenance (such as tightening the motor). You will also be limited to a single chainring on the front.

bafang bbs02b 750w electric bike kit
✅Link to Bafang BBS02B (trusted vendor on Aliexpress)

Mid-Drive vs Hub motor

Taking into account all of the above information it really boils down to your budget and the kind of riding you plan on doing.

In my experience, small hub motors are usually a lot less hassle than mid-drives in the long-term. Another thing to consider is pedalling resistance. Both the mid-drive and direct-drive hub motor produce a significant amount of resistance with the motor off.

Mid-drives are definitely much better at hill climbing, a 250w Bafang BBS01B will produce nearly 100% more torque than a geared hub motor equivalent.

mountain bike fitted with a 1000w direct drive hub motor

Hub motor kits have more of a ‘DIY look’ about them, there will be an external controller (usually in a frame bag), an external pedal assist sensor and lots of wiring to tidy up. Mid-drive motors definitely provide a cleaner and neater looking finished product.


If you are looking for a bit of help with hills but want to pedal under your own steam for a lot of the time, then a small geared hub motor would definitely be the way to go. If you are looking for a bike that will be able to tackle very steep climbs with ease, then maybe a mid-drive would be a better option.

Choosing the right e-bike battery

Battery choice is important because it will determine the kind of range you can expect from your electric bike.

First and foremost you will need a battery of the right voltage. Most kits are 36v or 48v, the 48v kits will usually take 52v batteries but this can in some cases compromise reliability. There are some motor controllers available that will take either a 36v or 48v battery but you will need to double check this first before making your purchase.

electric bike battery
✅Link to electric bike batteries (trusted vendor on Aliexpress)

The Ah (amp hour) spec provides a measurement of battery capacity.  In other words, it is an indication of how much energy can be stored by the battery. For example a 36v 13ah battery (36v x 13ah) will have a total energy capacity of 468Wh (watt hours) – using a constant 20Wh per mile would give a  range of approximately 23 miles. In real-world riding this figure could be much greater or lower depending on power level used, rider weight, the kind of terrain (flat or hilly) and wind direction.

The other thing to consider is the size / style of frame you will be fitting the battery to. Normal hybrid or hardtail mountain bikes of 18″ frame and above usually have plenty of space, but when you get down to 16″ frames, things can become a lot tighter.

full suspension mountain bike fitted with a bafang bbshd

If you have a full-suspension mountain bike then mounting a battery in the frame can be practically impossible (depending on the bike). Ladies framed bikes and step-through bikes are usually better suited to a rear rack-mounted battery.

It is advisable that you take measurements of your frame triangle before purchasing a battery. It is also worthy to note that some battery packs do not align particularly well with the bottle holder threads on the frame. If this is the case, you may need to drill and riv-nut an extra hole or two.

For more information on e-bike batteries please check out my article ‘electric bike batteries explained’

Thank you for taking the time to read this article, if you need any further help or advice choosing a conversion kit, please leave a comment below.

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Passionate E-Bike advocate and enthusiast since 2016. Riding an electric bike helped me to lose weight, get fit and reignite my passion for cycling!

22 thoughts on “Electric Bike Conversion Kit Guide – What You Need to Know

  • Hi Tony,
    I successfully fitted a TSDZ mid motor kit to my Dawes 27 inch wheel road bike in 2019. It was fine until I got intermittent cut outs of electric assist at low speeds. These became constant at speeds below about 8 mph. Digital speed is shown correctly but analogue speed goes to full scale as soon as the bike starts moving. It then reverts to showing the same as digital speed reading above about 8 mph and electric assist is back on. When analogue speed is at full scale it clearly exceeds the maximum speed setting for electric assist which shows on the analogue scale. This is presumably why electric assist is lost at lower speeds. I have tried in vain to get a replacement display. I presume the fault is in the display. I presume there is only one speed sensor signal and the display is at fault coming up with two different speed values. I have tried in vain to purchase a replacement display.The display type is an 850C Unfortunately the type number is not a unique definition. An 850C for Bafang looks the same but is different and does not work correctly with my TDSZ2.
    Can you help me find a source for a replacement display to fit the existing kit including wiring harness. I can send a photo showing the error situation on screen.


    Oliver Hinton

    • Hi Oliver,

      It does sound like a fault with the display. Although, I’d temporarily disconnect the speed sensor to see if that makes any difference as they can sometimes fail. Regarding getting a replacement display. OKfeet on Alixpress sell the 850c display which is configured to use with the TSDZ2 – here is a link to their product page on Aliexpress.


  • Hi Tony

    Any recommendations for a Pashley Princess e upgrade ??

    • Hi Susanne,

      The Pashley Princess is a tricky one as it has an internally geared rear hub and drum brakes. This would rule out either a front or rear hub motor. A mid-drive on the other hand should work, but there may also be potential problems with that. Assuming the Pashley uses a standard threaded bottom bracket (crank bearing) then something like a Bafang BBS01B 250w motor should fit, but you would need to remove the chainguard.

      A more straightforward solution would be something like the Rubee X friction drive system – this would clamp straight on to the seat post, but you would need to remove the rear mudguard for this to work.

      If you could swap out the front fork with something similar that has mounts for v-brakes, then a front hub motor with a rack-mounted battery would work well. I would contact a local bike shop or Pashley dealer to see if this is possible.

      All the best,

  • Hi Tony,
    I would like to hear your expert opinion.
    I want to convert my bike to an e-bike.
    My GIANT TROOPER 3500 bike is set to 28 “RIM (700C) or (622X19).
    1) The manufacturer indicates that for this rim the width of the compatible tire is from 1.1 “to 2.5” (28-62mm).
    2) On the other hand, in the Georg Boeder table, recommendations for choosing the width of the tire and rim, it is indicated that with an inner rim width of 19, the tire size according to ISO should not exceed 44mm.
    The first contradicts the second, who to believe and how to act?
    Because I plan to put Schwalbe marathon plus mtb 29×2.10 tires on my electric bike.
    What do you advise me to do when choosing tires?
    Sincerely, Vladimir.

    • Hi Vladimir,

      I would say 2.1″ (53mm) is a bit of the wide side for 19mm internal rim width. They would fit and they’d probably be just fine, but I would err on the side of caution. I’ve ridden with oversize tyres before without any major issues, but they tend to feel a bit squirmy on the back end.

      Looking at the Giant Trooper it looks like a hybrid / touring bike, I would make sure there’s enough frame clearance for 2.1″ wide tyres just to be sure.


  • Hi there Tony,
    I’ve got a 59cm Nashbar steel frame cyclocross bike (https://www.nashbar.com/nashbar-steel-cyclocross-bike-nb-sxia-50-p/p-re2eqweq3uaeyaa2) and was looking at the mid drive option you’ve reviewed (the tongsheng tsdz2 ebike kit). I was wondering if you’ve had any experience with this style of bike before. It’s set up with Shimano 105 gear set and I was wondering how difficult it would be to install something like the tongsheng. Thanks for all your help and wonderful website, it’s truly a gift.

    • Hi Brendan,

      I’ve convert quite a few road bikes in the past. Looking at the Nashbar, it has a standard FSA crank with thread bottom bracket, so the TSDZ2 should be a straightforward installation. You’ll be limited to a single chainring (42t standard), and you will need to adjust the indexing on the rear mech. The Q-factor is offset on the Tongsheng but you can fit the older style Shimano Steps cranks arms to improve this.

      I hope this helps, let me know if you have any more questions.


  • Hi I’m looking to convert a Scott genius mc20 carbon bike to a ebike the rear triangle is aluminium but the main triangle is carbon I really like this bike and apart from knee pain when pedalling uphill (arthritis)I have no problems so I’mm just looking for a bit of assistance uphill otherwise I just want to ride as normal I’m told the mid motor (which I would prefer) isn’t suitable for a carbon frame,so I’m looking at a geared hub motor I usually ride 30miles twice a week , I’ve measured the front triangle and a down tube battery would be tight ,the triangular battery would fit with the controller fitted underneath the diagonal downtube I would prefer a torque sensor to pedal assist the wheels are 26” which kit and battery would you recommend thanks in advance kev

    • Hi Kevin,

      If your Scott MC-20 is the 2007 model, then it should use a regular Shimano XTR threaded bottom bracket. If you can remove the crank and take a photo of the bottom bracket area and possibly take a measurement from the underside outside edge to the inner part of the BB shell, I can let you know if the Tongsheng TSDZ2 will fit. You can contact me through my FB page – there is a link in the header of this website. The torque-sensing hub motor kits available from China are supplied with a torque-sensing bottom bracket that requires a hole to be drilled in the underside of the BB shell (for the wiring), which isn’t a good idea on a carbon frame.


      • thanks for the reply tony ive been looking into it and now im thinking of a rear hub motor and the pedal assist sensor ( no drilling req) i like the sound of the bafang g320 geared hub motor the wiring supposed to be better not coming out of the end of the axle also its supposed to be silent ,i mainly want to pedal the bike as normal most of the time with a bit of assistance on the hills, also the g mac looks good with brake regeneration ,also because of the frame geometry a downtime battery would be tight ,i do like the idea of the grin with the controller built into the battery holder ,but the hardcore triangular battery would fit betters there a kit you would recommend for my needs”””””’i normally ride about 30 miles twice a week ,but if the battery flattened i would like to be able to ride the bike as normal as possible, apart from the extra weight ,where can i buy from-what about shipping and import taxes to the uk thanks in advance kev

        • Hi Kev,

          I’ve just messaged you on FB. Checking availability with suppliers.


  • Hi Tony,
    Just swapped out a broken Yose Power kit on my wifes Santa Cruz ultralight, all is good other than I had to fit the PAS on the crank side rather than the left due to the size of the bottom bracket, it’s on and reads fine, but only when peddling backwards. there is an option to reverse the direction of the sensor on the c500-lcd control unit but it either doesn’t work or won’t set. opened the wires up to see if I could swap them to reverse the sensor but the obvious swap makes no difference.( live red blk and wht, assumed swapping the blk n wht would reverse, but still reads backwards). Any ideas most appreciated, thanks, Neil

    • Hi Neil,

      If your kit uses the split magnetic sensor disc, sometimes just turning the disc around will sort the problem out. If that doesn’t work you may need to buy a crank-side specific sensor and magnetic ring – these are usually available from eBay and occasionally Amazon. The Yose Power kit uses a 3-pin higo connector for the PAS sensor, if you can find an alternative with a similar connector it will save you the need to cut and splice the existing connector – the 3 wires are live, ground and signal. Sometimes different sensors use different colour codes for the wiring, so you may need to figure that out through trial and error (most manufactures will have a wiring diagram available).

      I hope this helps, if you have any more questions, please let me know.


  • Hi Tony, I read in your other post you stated “You would definitely need a 30A BMS for the BBSHD – unless you reprogrammed the controller and limited the maximum current to 25A (which would defeat the object).”
    If I plan to run a 48v 13ah battery, what is the problem with limitng the max current to 25? ie-why does that defeat the object. The motor is rated to 1000w, but at 48v that power is achieved at around 20A. I am concerned with the lifespan of the BBSHD when running, so why would you need a 30A output when that well exceeds the 1000w of the motor?

    Sorry if it’s a stupid question, I am exploring the idea of running the BBSHD on my mountain bike.

    • Hi Jim,
      There’s absolutely nothing wrong with limiting the max current to anything you see fit. What I meant by ‘defeating the object’ is in my experience, most people spend the extra money on the BBSHD (over the BBS02 750w) for the full 1500w+ power output. I used to own a BBSHD and found it produced more than enough power in the lower assist levels, with the added benefit of increased torque, efficiency and durability. I know a couple of owners who have limited their motors to 18A and still very rarely need to use full power mode. In my opinion the BBSHD is worth the extra money over the BBS02 simply because it’s a more robust and reliable motor.

      All the best,

      • that’s great to hear! I am mostly looking to do some trail riding, dealing with hills on the way to these trails gets tedious. I am not one for top speeds on these bikes. Just looking to cruise along to the trails at a comfortable 30-35kmh with pedalling. Is there any sort of battery size you’ recommend?

        • For a good all-rounder, something like a 48v14Ah or thereabouts. Since you’re not going to be hammering the hell out of it in full power mode, you should be able to get a fairly decent range off one of those. I just had a quick look on eBay Australia and there’s quite a choice. If it’s going on a Hardtail MTB you should be fine for clearance. Here is a link to a decent one that uses Samsung cells.


  • Thanks for the excellent resource website – truly great work and has made for fascinating reading since I decided to energise my 26” framed Trek 700c hybrid with a powered conversion for my 15m west/east London commute. I’m 6’6” and a chunky lump so will need some grunt, but I don’t fancy arriving at work dripping with sweat, so your recommendation of the ebikeling 700c 1200w kit looked great. Only issue – any idea where can I buy one in the UK? They wont ship & I don’t want to wait for 60 days shipping in from PRC……

    • Hi,

      I’ve found a supplier on eBay who offer a similar kit (1500w 48v 700c rear hub motor). They ship from Spain, so delivery shouldn’t take too long – Here is the link.

      Glad you’ve find my website useful, if you need any more advice let me know.


  • Thanks for the brilliant website…. lots of good advice. During the lockdown I have dragged my old commuter bike out out of the shed and put it back into service. I to regularly ride to work, but when I moved to a very hilly area it was relegated! I am now thinking that with some electric power I could start using it again……

    The complication is that it has a Shimano nexus 7 speed hub gear with a back pedal brake. That means either front hub motor, or convert to derailleur or….. would a mid mount conversion work with the hub gear….. or would it just break it?

    Any suggestions bearing in mind good hill climbing is a key for me


    • Hi Geoff,

      Thanks for your complements, glad you like my website.

      There is a version of the Tongsheng TSDZ2 mid-drive that works with a coaster brake – here is the link.

      In my experience Shimano Nexus and Alfine hub gears work fine with moderately powered mid-drive motors. I have even installed several Bafang BBS02 750w motors to bikes with Nexus 8 hub gears without any long term issues. The Bafang doesn’t support the coaster brake function though.

      The Tongsheng is a good motor in my opinion, if you opted for the 350w or 500w version, that should give you enough assist for steep hills. I have tried these motors on 25% – 30% gradients and you still need to put a fair bit of effort in, but it doesn’t turn your legs to jelly!

      If you need any more advice, please let me know.

      All the best,


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