At Electric Pedal Power in Melbourne's South East, we've spent years selling, installing, riding and working on high-power electric bike conversion kits. One of the most exciting systems we've worked with is the CYC X1 Pro Gen 4 mid-drive conversion kit.
The X1 Pro Gen 4 sits at the extreme end of the electric bike conversion market, with up to 6,000W peak power and 280Nm of peak torque according to CYC's current specifications.
With the right battery, setup and gearing, these kits can turn a suitable mountain bike into an incredibly powerful off-road electric bike, with approximately 5–6kW of usable peak power, around 90km/hr potential top speed and massive hill-climbing ability.
But there is one part of the bike that can struggle to keep up with all that power.
The bicycle drivetrain.
That's why Electric Pedal Power is currently developing the CYC Bullet-Proof Drivetrain — a heavy-duty drivetrain package specifically designed around the demands of powerful CYC mid-drive electric bike conversions.
Why does a high-power mid-drive need a stronger drivetrain?
A conventional electric bike with a rear hub motor puts the motor's power directly through the rear wheel.
A mid-drive electric bike is completely different.
The motor drives through the bicycle's chain, front chainring and rear sprocket. This allows the rider to take advantage of the bicycle's gearing and multiply the torque at the rear wheel.
That's one of the major reasons powerful mid-drive electric bikes can climb incredibly steep hills.
But there's a downside.
All that motor power is being transferred through components originally designed primarily around human pedalling.
A CYC X1 Pro Gen 4 can produce vastly more torque than a normal cyclist can generate through the pedals. CYC currently lists the X1 Pro 4 at 280Nm peak torque, making it a seriously high-powered mid-drive system.
The chain, front cog and rear cassette therefore become critical components.
Chains can stretch, break and suffer under heavy loads
One of the most common issues we've seen with high-power mid-drive electric bikes is accelerated chain wear.
A chain that may last a long time on a conventional bicycle can experience a very different life when it is repeatedly subjected to thousands of watts of motor power.
Heavy acceleration, steep hill climbing and sudden changes in load can all put enormous forces through the chain.
Gear changes can be particularly hard on the drivetrain.
When the motor is producing substantial torque and the rider changes gear, the chain and sprockets can experience a sudden shock load. Eventually, chains can stretch, wear excessively or even break.
And once the chain starts stretching, the problem doesn't stop there.
Rear cassettes can quickly become worn
The rear sprockets are another major weak point.
Under repeated high-power use, the teeth on the rear sprocket can wear rapidly. Eventually, the teeth can develop the familiar "shark fin" appearance, where the sprocket teeth become hooked and distorted.
Once this happens, the chain may no longer properly engage with the sprocket.
Instead, the chain can begin jumping or slipping under acceleration.
With a powerful mid-drive, that can happen at exactly the wrong moment — such as when climbing a steep hill or putting the power down off-road.
Eventually, the bike can become effectively unrideable until the drivetrain is replaced.
This is one of the main reasons we believe there is a genuine need for a heavy-duty electric bike drivetrain specifically designed for high-power mid-drive conversions.
Introducing the CYC Bullet-Proof Drivetrain
Electric Pedal Power is currently working with a local fabrication shop in Melbourne's South East to develop our new CYC Bullet-Proof Drivetrain.
This project has been developed from years of real-world experience with electric bike conversion kits, rather than simply designing a product on paper.
We've seen what fails.
We've replaced the chains.
We've replaced worn cassettes.
We've seen chains break.
We've seen customers lose drive because the chain is slipping over a badly worn rear sprocket.
And we've experienced the demands of powerful mid-drive electric bikes ourselves.
The goal is therefore straightforward:
Build a stronger, simpler and more reliable drivetrain for high-power mid-drive electric bike conversions.
What will the CYC Bullet-Proof Drivetrain include?
The initial drivetrain kit is being designed to include:
- Heavy-duty 219H chain
- Heavy-duty front cog/chainring to suit 219 chain
- Heavy-duty rear cog to suit 219 chain
- Suitable chain tensioner
- Components selected specifically for high-power mid-drive electric bike conversions
The chain tensioner is an important part of the system.
A high-powered mid-drive needs to maintain good chain tension to reduce the chance of excessive slack, chain movement and chain drop.
Rather than trying to make a conventional bicycle drivetrain cope with extreme power, we're designing the system around the way these electric bikes are actually being used.
Designed for CYC X1 Pro Gen 4 and similar high-power mid-drives
The initial focus is the CYC X1 Pro Gen 4 mid-drive conversion kit, along with similar high-power mid-drive electric bike systems.
The X1 Pro Gen 4 is designed specifically for extreme power, off-road and utility applications and is compatible with a wide range of bicycle frames. CYC currently lists compatibility across 36–72V systems, with 32T–40T chainring options and multiple bottom bracket configurations.
This makes it an incredibly versatile electric bike conversion kit.
It can also be tuned through the CYC system depending on the rider's requirements.
But if you're building a serious 5–6kW electric bike conversion, particularly one capable of approximately 90km/hr and extreme hill climbing, the drivetrain needs to be treated as seriously as the motor, battery and controller.
Why we're moving away from traditional shifting
The first version of the CYC Bullet-Proof Drivetrain will not be designed around conventional gear shifting.
This is intentional.
A multi-speed bicycle drivetrain is fantastic for a normal bicycle because it allows the rider to select different gears depending on the terrain.
But with a very powerful mid-drive electric bike, shifting under heavy motor load can introduce enormous stress into the chain and sprockets.
Rather than trying to retain every feature of a conventional bicycle drivetrain, we're prioritising:
Strength.
Reliability.
Simplicity.
Torque.
The rear cog will be available in a couple of different sizes so customers can choose a setup more focused on maximum torque and hill climbing or one that provides higher top speed.
The drivetrain is not expected to retain conventional shifting.
For a high-power off-road electric bike, we believe this is a worthwhile trade-off.
What about cassette and freewheel compatibility?
The initial CYC Bullet-Proof Drivetrain is being designed primarily around modern cassette-style rear hubs.
We aren't currently developing the first version around traditional spin-on freewheels.
This reflects the type of bicycles most commonly being used for high-power CYC mid-drive conversions.
Most of the customers looking at a CYC X1 Pro Gen 4 are starting with a relatively modern mountain bike or higher-end bicycle, rather than an older bicycle using a basic screw-on freewheel.
We may look at additional compatibility options in the future, but our first priority is building the strongest and most practical drivetrain possible for the bikes these powerful mid-drive kits are typically installed on.
Why choose a mid-drive electric bike conversion?
A powerful rear hub motor conversion can provide plenty of performance, but a mid-drive offers something different.
The motor sits centrally around the bottom bracket rather than inside the rear wheel.
This gives the finished electric bike a low and centrally positioned motor, helping keep the weight distribution closer to the centre of the bike.
The result can be a much more natural-looking and discreet conversion, particularly on a modern mountain bike.
The ability to use gearing is another major advantage.
Instead of relying on a fixed motor-to-wheel ratio, the mid-drive can use different gearing to deliver substantially more torque at the rear wheel.
This is particularly noticeable when climbing steep hills or riding difficult off-road terrain.
It's one of the reasons high-power mid-drive electric bikes have become increasingly popular internationally.
And with systems such as the CYC X1 Pro Gen 4 pushing into the 5–6kW peak power range, the performance can be seriously impressive.
Developing the drivetrain locally in Melbourne
One thing that is important to us at Electric Pedal Power is that this project is being developed locally.
We're a small, growing electric bike business based in Cranbourne West, Melbourne's South East, rather than a huge overseas manufacturer.
We've spent years working directly with electric bikes, electric bike conversion kits, batteries, motors and customers.
That means we're seeing the real-world problems that riders experience.
The CYC Bullet-Proof Drivetrain is the result of that experience.
We're working with a local fabrication shop to refine the components and get the first production version ready.
We're not claiming that any bicycle drivetrain can literally never break. A high-power electric bike being ridden aggressively, jumping, landing heavily or running with poor maintenance can break almost anything.
The goal is instead to create a drivetrain that is far better suited to the extreme loads produced by high-power mid-drive electric bike conversion kits. Better than current heavy-duty CYC drivetrains on offer.
Pre-production is coming soon
We're expecting the CYC Bullet-Proof Drivetrain to enter pre-production within approximately two weeks of publishing this article.
The first version will primarily target the CYC X1 Pro Gen 4 and similar high-power mid-drive electric bike conversions.
If you're running a CYC X1 Pro Gen 4, planning a 5–6kW mid-drive electric bike conversion, or simply tired of replacing chains and rear cogs, we'd be interested in hearing from you.
We're also happy to discuss the appropriate gearing depending on whether your priority is hill climbing and torque or higher top speed.
The final pricing will be confirmed once the first production components are completed, but our aim is to keep the drivetrain affordable enough to be a practical upgrade rather than another expensive component.
If you're in Melbourne, South East Melbourne or elsewhere in Australia — or you're building a CYC-powered electric bike internationally — contact Electric Pedal Power to enquire about the upcoming CYC Bullet-Proof Drivetrain.
We've spent years finding the weak point. Now we're working on fixing it.