The DIY E-Bike

Want to retrofit your current bike as an electric-assist bike? Here, Caleb Magoon, owner of Power Play Sports and Waterbury Sports shows you how.


Electric bikes are here to stay. Some buyers are older folks who want to stay in shape and for whom having a throttle option gives a sense of security. Others are recovering from injury or simply don’t have the stamina to navigate Vermont’s prolific hills. Some enthusiasts are simply extending their range or making a challenging commute more doable. Overall, these bikes open up the cycling market to many more people.

For more about e-bikes and who is using them (you may be surprised), click here.

While a new e-bike can cost as little as $649 (for an entry-level cruiser you might find at Walmart), a cheaper bike may not be reliable. And if you don’t want to spend upwards of $1500 to have a mid-range e-bike or deal with the hassle of having yet another bike in the garage, you might want to think about converting an existing bike.

While converting the bike you have into an e-bike isn’t an option for everyone, it does offer a cost-effective way to get people into the new market. Bike conversion kits cost anywhere from $500 to $2,000. The one big drawback? Installing a motor will void the manufacturer’s warranty on your bicycle.

Robert Coates is the motor install specialist at Power Play Sports (PPS), one of the two shops I co-own, and has been doing motor installations on bikes for over four years. He has led the way for e-bikes at our shop and has the skills to give a customer exactly what they want from a custom motor conversion.

Know What You Want Your Bike to Do

Before you convert an existing bike, think about how you plan to use it. Not all conversion kits fit with every bike. Motors can be a front wheel, rear wheel or mid-motor mount, where the crank is replaced. Each has advantages and disadvantages outlined below.

Throttle: Just like on anything else with a motor, this is the “Go” button or lever. Most, but not all e-bikes and conversions have one. These are great as a safety feature.

Electric Assist: Again, some but not all conversions will have this. The idea is simply this: when you pedal, the motor gives your natural motion a little extra juice. Most e-bikes allow you to select the amount of assist the motor gives you on a scale of 1 to 5 or 1 to 10. These have a much more natural feel when riding and will allow you to go faster and further more easily.

Hub Conversion Kits: In this type of conversion, which is the least expensive, your wheel hub is replaced with a motor that spins the wheel. The down side is that it adds a big weight to the front or back of your bike. This  alters the weight balance of a bike so that it doesn’t ride as well as with a mid-motor mount. In the case of a front wheel hub motor (the least expensive option within this category) you won’t be able to enjoy pedal assist—only throttle.

Mid-Motor Mount Kits These are the most expensive, but best option for all around use. These conversions best preserve the balance of the bike, and all options include pedal assist and throttle. The feel of a mid-motor pedal assist is superior to that of a rear wheel hub conversion, as the cranks and drivetrain are being driven, instead of just the wheel. It’s the most natural feeling ride.

If you are ok with a slightly higher price tag, we recommend a mid-motor mount. Not all bikes can be converted using one of these kits (hub mounts can be installed on nearly anything), but they are the better option all around.

Choose Your Motor

Choosing a motor and battery to drive your converted e-bike is your next step. Some of the following motors are “street-legal” and some are not, so check your local laws before you select one. No matter which kit you get, there should be a variety of motor sizes available to you.

Here are some easy guidelines for choosing how much power you’ll need.

300-400 watts: These smaller motors are great for minimal assist needs (less power, less speed). Think: a tough guy who wants minimal assist, or someone living in the Champlain Valley with lower, sloping terrain.

600-800 watts: Excellent bang for your buck in terms of power. A motor of this size will give you plenty of oomph for the hillier parts of the state without requiring a massive battery. For folks who need the pedal assist function and know they need to navigate steep or loose terrain, this is a great starting point.

1K+: These are the big boys. Keep in mind that a bigger motor requires more battery power. These are awesome, mostly off-road motors that really have a kick. They have plenty of power for getting over any obstacle and a maximum legal speed of 29 mph. Because of their size, they also tend to be a bit more rugged. At this size and price, few manufacturing shortcuts are taken. These motors tend to be extremely durable.

How Big a Battery? 

At PowerPlay Sports we recommend a couple of different motor and battery options depending on your intentions. However, if you are going online to buy a kit, ask the company you are buying it from which battery is most appropriate for the motor.

Batteries are generally measured in volts and amp hours to roughly describe the amount of power flowing to the motor at a given time. This can get extremely technical very quickly. Without going crazy, you will generally want a battery with more voltage for a bigger motor. Battery sizes range from 36 volts for a smaller motor to 54 volts for bigger motors. Most companies are happy to give you a recommendation, so don’t hesitate to ask what they think is most appropriate for the motor you want to drive.

These components and kits are available online from a number of sources. But once again, make sure you know who you are getting them from and how they handle warranties. If you are not consulting a bike shop or an expert, do a little more research to be sure you know what you are getting.

There are also a lot of optional parts available for e-bike conversions that can further improve comfort and safety. Motor cutoffs are an important safety feature that cut the motor when you change gears or hit the breaks. They can be complicated to install as each must also match the existing hardware on your bike. Once again, doing a little extra research or talking to an expert will help you determine if these extra features are right for you.

How to Retrofit Your Bike as an E-Bike

While ordering the parts and installing the kits is doable for the average consumer, the kits are fairly complex. Directions are often not included and online instructions tend to be incomplete. There are also some specialized tools and additional small parts that will likely be needed. They can be found at any bike shop, but add yet another level of complexity. So while a home installation is possible, having a bike shop complete the task is always the easiest route.

These installations take anywhere from less than an hour for a basic front wheel install to several hours for a more complicated hub or mid-motor retrofit. Thus, an installation could cost as little as $50 or as much as $500 for a big conversion. Many run right in between. Keep in mind, there is often a need to install smaller parts and replace things like your derailleur cable when you put in a motor cutoff. For this reason most shops will simply sell you a whole package that includes labor and any small parts needed. 

You can convert your existing bike into an e-bike, but you may want a shop to help. Photo by Caleb Magoon

However, if you want to do it yourself, go to town! Here’s what you need to do on an average mid-motor install (our most popular option). This installation takes us about three hours—you should expect a bit longer.

Before you do anything, make sure your kit is compatible with your bike. You will also need some specialized bike tools to complete the process.
Once you have the tools you need and a kit in hand, here’s what you do:

a) Remove your pedals, existing crank assembly and bottom bracket (in this order).

b) Assemble your new motor by installing the chain ring and guard onto the motor.

c) Install the new motor and bottom bracket on the frame, fastening them with the provided bolts and lock ring. Sometimes spacers need to be added for exact fit. We also recommend use of a light-strength locktite.

d) Remove one grip/shifter/brake lever to slip on the new throttle. Attach power control and computer/interface.

e) Attach the battery mount to your water bottle cage/accessory mounts. For a small frame, you may need to attach the battery to a back rack.

f) Install the wiring harness connecting the wires from the components on the handlebar down to the motor and the battery. Attach the motor to the battery. Try and keep the cable runs as clean and neat as possible!

g) Add-ons: Some kits will give you new brake levers to install while others will provide add-on magnetic disconnects for the existing levers. These should connect right into the wiring harness. The gear disconnect will require you to cut the housing and re-route your derailleur cable through the cutoff. The cutoff should connect easily to the wiring harness. Lastly, there should be a speed sensor that attaches much like a standard bike computer to the rear of the frame, with a sensor on a spoke.

h) Attach the battery and turn it on, along with the control module. Once they’re hooked up and everything runs, neatly arrange and tie up your cables with zip ties.

As the electric bike market develops, the only thing you can really count on is that we will see lots of changes in the coming years. The revolution these bikes should bring will make biking accessible for a huge number of people who can’t currently enjoy the sport. As always, if you are considering an electric bike, your best resource is a local bike shop. We have a tremendous bike community in Vermont and it’s just a matter of time before many of these options are available in your local store.

If you’re considering a new e-bike, don’t be deterred by the price shock. Conversions are more affordable and options can be selected to keep the price down. Additionally, prices on integrated e-bikes will only come down in the future. While the price does remain an obstacle for many, rebates are currently available from Burlington Electric and Green Mountain Power.

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