How to Convert a Road Bike to an Electric Bike

Since the going rate for an excellent electric bike is around $2,000, you may be wondering if you can save money by converting your existing road bike to an electric bike.

Yes, you can. Any road bike can be converted into an electric bike. Converting the more affordable models to electric should be a breeze in most cases.

Benefits of Converting a Road Bike to an Electric Bike

Buying a conversion kit is more cost-effective than purchasing a new electric road bike in the United States. The average price of a brand-new electric road bike is more than a conversion kit.

Adding a mid-drive system or a small rear hub motor isn’t as challenging as you might think, even if your current setup isn’t ideal.

Think about your home’s location. If you live where the landscape is as level as a bowling green, the daily bike commute will be a breeze.

On the other hand, living in a hilly region can make it challenging to cover large distances using a road bike. In this case, an electric bike comes in handy.

The main advantage of converting an old road bike to an electric assist is the financial ease. You can save money by purchasing a used beginner road bike and turning it into an electric bike.

How do You Know if a Road Bike Can be Converted into an Electric Bike?

Many factors will determine whether or not your bike is suitable for the job. They are primarily concerned with your bike’s bottom bracket, frame material, and wheel dropouts.

Bottom Brackets

If you add a mid-drive, the type of bottom bracket your bike uses will be crucial. In most cases, standard square tapered cartridge bottom brackets are included.

This sensor is meant to be fitted on the non-drive side of the cartridge.

Most road bikes will have either Octalink/ISIS internal or external cup bearings. The pedal sensor for hub motors must be tailored to the unique characteristics of the bike.

The pedal assist sensor can be installed on the electric road bike.

If the bottom bracket shell on your bike is 68 mm-73 mm wide and 33.5mm in diameter, you can use a mid-drive.

 If your bike uses a press-fit bottom bracket, you can get away with using just a hub motor instead of a mid-drive.

Frame Material and Wheel Dropouts

The thru-axles on modern road bikes make it impossible to install a standard rear hub motor; however, the traditional dropouts on older bikes make it easy.

The frame material of a road bike plays a crucial role in making the transition to an electric bike. The extra weight of a conversion kit is too much for these frames to manage.

Steel Frames

A steel-framed touring bike is one of the best conversions to electric power. Steel is one of the best materials for an electric bike because these bikes are designed to haul more people and gear.

The main disadvantage is that adding an electric conversion kit and a medium-sized battery increases the donor bike’s weight by about 20 pounds.

The most widely available road bikes include aluminum frames and carbon forks. You can also use alloy frames with either mid- or rear-hub motors.

However, a torque arm should be installed before a rear hub motor to prevent the wheel from escaping the dropouts.

Carbon Fibers

Full carbon frames cost more than steel frames; however, they are an option. New carbon-framed bikes typically use a press-fit bottom bracket.

Despite carbon fiber’s incredible strength, the frame experiences considerable strain from the 2.5-kilogram rear-hub motor.

While several carbon-framed electric road bikes are available, the X35 e-bike motion motor is noticeably lighter than the typical retro-fit hub motor.

Even though your bike has a threaded bottom bracket, the area around the BB shell might have been beefed up in preparation for a mid-drive.

This preparation mode can make it nearly impossible to fit the motor into the housing because of the severely reduced clearance between the motor shaft and the housing.

Front Hub Motor-Assisted Drive

Front hub motors are available; however, most mechanics advise against them due to the prevalence of carbon forks on road bikes. Steel forks allow the use of a front hub motor.

Things to Consider Before Turning a Road Bike into an Electric Bike

The following are some critical factors that should be considered before turning an ordinary road bike into an electric bike in the US:

1. Weight

You can safely ignore the weight of your donor bike, as you have to add 6 and 8 kgs to the finished product. If you want the lightest bike possible, you’ll have to go for the most expensive upgrade.

Choosing the right battery size requires thinking about weight and range. As the battery range grows, the battery’s weight will climb considerably.

A standard 36V 8Ah compact battery does not weigh more than 2 kilograms, while a 36V 20Ah battery would weigh more than 4 kilograms.

Long-lasting batteries are a smart purchase. Moreover, the dreaded range anxiety won’t affect your performance.

2. Chainlink

The front chainring will be positioned 5-15mm farther from the crank than the big ring, typically because of the engine’s design.

The ‘dished in’ design of the standard 42-tooth chainring included with the motor helps address this issue. However, the indexing will be terrible if you use a regular 110BCD chainring.

In its legally proper default setup, the TSDZ2 will stop assisting once your cadence reaches about 90 revolutions per minute (rpm).

There could be dependability issues. Any electrical device, including the TSDZ2, is susceptible to failure. You can expect a small percentage of defective motors because of the high production volume.

3. Power

The Bafang motor can go from 250w up to 1000w. The 1000w BBSHD works, but it’s more suited to mountain riding due to its nearly 5kg weight.

Bikers in the United States and Australia cap the power output of motors at 250 watts. If your engine can go quicker, do so at your own risk.

The initial conversion to Bafang will not only help you on two wheels but also pave the way to upgrade to a regular bike.

4. Battery

You must consider how much range you need and how often you plan to use the electric assist when deciding on the battery.

Consider a tiny bottle battery to lighten your load and maintain a covert profile. You can use the bottle cage provided.

36-Volt, Bottle-Shaped Battery

Alternatively, you can conceal a power pack inside a relatively small backpack and attach it to the bike’s pannier rack.

The size and energy capacity of the battery you choose will significantly impact the total weight you add.

 Keep in mind that different sizes of batteries have vastly different weights. Small batteries might only weigh a few kilograms. A high-power 36v 21Ah battery might weigh more.

Electric Conversion Kit

It depends on your tastes. The transformation into an electric bike will impact not only the visual appearance but also the weight and general feel of a regular bicycle.

Tongsheng TSDZ2 mid-drive motors and compact bottle batteries, which are about the size of a large water bottle and usually fit in a standard bottle cage, are considered the best covert setup.

Adding this system to your bike will only cause a weight increase of 5.6 kilograms. It has a stealthy, lightweight design and excellent torque-sensing pedal assist function.

On the other hand, increased resistance makes pedaling more of a challenge. At speeds above which the aid no longer applies, more drag will be experienced even with a mid-drive.

Bafang’s Performance

In contrast to the TSDZ2, the Bafang motor can’t be locked to prevent it from pivoting in the bottom bracket shell. Bafang has introduced a steel mounting plate toothed on the bottom but smooth on top.

After installing the engine on a bike with an aluminum frame, the assumption is that the lockring’s teeth will sink into the alloy surrounding the BB shell, preventing the shell from slipping.

Pedal assistance from the Bafang mid-cadence drive may not be as intuitive as that from Tongsheng’s torque sensor; however, it’s more reliable.

You can also fine-tune the assist settings via a USB connection and the company’s free setup program.

When using an electric motor, getting the shaft spinning as rapidly as possible is vital to avoid the engine overheating and maximize its performance.

Make sure the power on the Bafang and all succeeding ones increased smoothly. This way, you will require less effort from the controller.

Ultimately, it contributed to a more natural experience with electric assistance while reducing energy use.

The Bafang mid-display drive’s adaptability is another advantage. The C965 and the SW102 mini-display are excellent options for a road bike due to their compact size and stealthy design.

Although the Bafang has a smaller Q-factor than the TSDZ2, it is still much larger than a tiny crankset. All redesigned mid-drives suffer from a chain line compromise.

 You should be alright if your tape player only goes up to 8 or 9 speeds. However, the indexing quality may decrease at greater rates. You could try adjusting the rear derailleur’s tension to see if it helps.

Wheel Hub Motor Electric Conversion Kit

Installing a hub motor in a road bike is the most practical method of adding electric assistance. Many popular brands use the X35 e-bike motion rear hub motor in electric road bikes.

A 250-watt rear hub motor often has a smaller diameter than the 32-tooth cog on an 11-32 cassette. Hub motors are typically lighter than their mid-drive counterparts.

The most noticeable benefit is the complete absence of resistance when pedaling with the assistance switched off.

 Therefore, if you occasionally need help, hub motors are ideal. However, the motor and batteries add some extra weight.

You can use your existing bottom bracket and crankset with some hub motors. The freehub allows for a 10- or 11-speed cassette. They are generally reliable.

Adding an electric hub motor to a road bike has numerous benefits.

Durability increases as the number of miles driven increases. Hub motors are significantly more trustworthy than mid-drives over a vehicle’s lifetime.

Installing a Hub Motor Conversion Kit on a Road Bike

Less efficiency

Hub motors aren’t quite as efficient as mid-drives and can’t match their torque output. Battery life will be slightly reduced using a 250-watt hub motor instead of a similar-sized mid-drive motor.

Additional Controls and Sensors Add Complexity to the Wiring

The installation is typically less tidy than with a mid-drive. Remote controls and pedal sensors are standard components of hub motor conversion kits.

Pedal-Powered Speed Aids can be Detected Using Cadence Transmitters

Since most commercially available hub motor e-bike conversion kits only incorporate sensors to detect the rider’s cadence when pedaling, the electric assistance feels on/off.

The use of cadence-based pedal sensors can be helpful for those who have difficulty pedaling because of pain or discomfort. Pedal rotation generates motion, and the motor supplies the necessary force.

Inefficient Pedal Assist Systems

Pedal assist systems that rely on cadence are inefficient compared to those that measure torque.

A torque sensing system keeps track of how hard you’re working on pedaling and adjusts the level of help it gives you, making the ride feel more natural.

Adjustable Tires

A 36h lace pattern is necessary for most aftermarket hub motors. Your wheels will have a machined braking surface for rim brakes. They will be compatible with a standard disc rotor.

If your bike has been installed with all-black disc wheels, you should purchase a matching black rim and have the motor connected to that.

Stainless steel silver spokes are included with many hub motor kits. However, they may not match your front wheel spokes’ color scheme.

A hub motor is the best option for your road bike if you only require help on hills and want to reduce tiredness when riding long distances.

 If you ever wish to ride your bike without the motor and battery installed, it takes less than five minutes to switch out the rear wheel and remove the battery.

To keep weight and maintain a stock appearance, you should purchase a hub motor kit (without a wheel) and have it laced into a rim that complements your bike.

Final Words

Choosing the best e-bike conversion kit for your road bike will depend on various factors. The choice between a hub motor and a mid-drive system comes from personal preference.