The complete guide to e-bikes

Electric bikes (e-bikes) have become the fastest growing  bike category in the world in recent years, transforming cycling in a way few had predicted.

They combine battery powered motors with your own pedal power, giving the bike added umph. It’s a technology that’s been made possible by ever-improving battery designs and has opened up a new world of cycling for many.

There are many different types of e-bike, with variations in motor placement, and control. 

An e-bike’s motor can be found at the front, rear or centre of the bike, but in this article we'll mostly be focused on those located in the central crank area.

That’s the overview, now onto more detail on e-bikes and why you should consider adding one to your fleet. 

What are electric bikes

There are two main types of e-bike, ‘electrically assisted pedal cycles’, or just ‘pedal-assist’, and those with a ‘throttle’ that don’t require the rider to pedal. In this article, we’re concerned only with the former.

In most e-bikes of this type, the motor kicks in when it senses that torque has increased by a certain amount. These pedal-assist e-bikes call on the motor only to provide assistance; it won’t move forward on it’s own power.

The motor then supplements your pedal power when you’re under strain, allowing you to climb gradients more easily. So it won’t kick in while you’re freewheeling downhill, for example.

Basically, we're not talking about a moped, which is powered exclusively by its motor – on an e-bike, you still need to pedal for the motor to work. And, if the battery runs flat, you can still pedal home as if it were a normal bike.

Road, gravel, commuter and MTB e-bikes

Whether you're a roadie, an MTB'er, a gravel rider, or even just a weekday commuter, there is an e-bike out there for you. 

Pedal assist technology has been incorporated into each of these styles, and the style of this incorporation has become increasingly sophisticated with every iteration. So, modern e-commuters remain robust and fun, e-MTBs continue to be agile and responsive, while e-road bikes are just as sleek and accomplished as their manually powered forebears. 

A great example is the Nukeproof Megawatt, an e-bike version of the famous Nukeproof Mega, used by Sam Hill to win three UCI Enduro world championships. The Megawatt won the 2022 MBR eMTB of the year, with it's in-built battery doing little to encumber this beast of a bike. 

Are e-bikes legal and how fast can they go?

Electric bikes are completely legal, but their top speed and power is capped for safety reasons. In the UK, the pedal assist is limited is 15.5mph while power output is capped at 250 watts. Without these caps, you would need a full UK driver’s license and would have to register the vehicle for tax and insurance like any other motor vehicle.

How does a electric bike motor work? 

Electronic motors, fitted most commonly to the bottom bracket, propel the bike forward when a rider pedals. Pedal assistance is applied when sensors recognise one of the two following circumstances.

• For mid to high range e-bikes, sensors measure and regulate how much effort you put into each pedal stroke, known as torque. When it recognises you are putting more power down, assistance will be directed via the motor.
• For entry level e-bikes, sensors may measure cadence, which is the pedal rate of the cranks. If you pedal slower, this increases the power output.

Sensitivity and modes can often be adjusted using buttons on an electronic display. These sensor types are often coupled with an automatic throttle which moderates the motor independently.

Electric bike motors

There are a number of brands that build e-bike motors, but the market is dominated by three - Shimano, Yamaha and Bosch. These brands create the pedal-assist crank motors you’re most likely to find on electronic road, MTB, gravel, and commuter bikes.

However, aside from central drive motors, there are two other types of drive systems which you may want to choose depending on your intended use. Here's a quick guide to all three. 

1. Central drive motors – Central drive motors are the most common and found underneath the rider in the bottom bracket. Due to their placement, they have a lower centre of gravity, making for a balanced, grounded, and stable riding experience. These are commonly found on electric mountain bikes and mid to high range bikes. With this top end power, you need be sure to keep a regular check on the chain and component wear.
2. Rear hub motors – Hubs are the central part of a wheel that link spokes to the rim and fixes onto the frame. Rear hub motors offer slightly more rear traction and stability, with a lighter front and heavier rear. As power is directly applied to the gears and chain, the added mechanical complexities raise the cost of the setup and also increase wear.
3. Front hub motors – Front hub motors are the more affordable and will drag you forward just like a front wheel drive car. With the motor being up front, this design is better suited to long flat rides and commuting. The best part about front hub motors is that they are independent of the chain and drivetrain parts, meaning there is less wear and tear.

For front and rear hub motors, you have two types of motor technology, but both require a purpose-built wheel to house the motor in the hub regardless of which you choose.

• Geared motors accelerate fast but peak their top speed soon due to their size. For geared motors, as the name suggests, they rely on small cogs inside the hub motor, working efficiently to deliver power. They’re slightly louder but are very effective both on cost and power.
• Direct drive motors accelerate slower but offer a faster top speed. Direct drive motors have a hub shell that attaches to the spokes and wheel rim but spins independently of the inner hub. The inner hub motor doesn’t rotate but emits magnetic forces from a coiled wire. This spins the hub and the wheel. As momentum builds, you reach a high-top speed.

How long do electric bikes last?

Much like electric cars, one of the reasons e-bikes took so long to go mainstream was the limitation of batteries. But, fear not - modern battery technology has come a long way, and their capacity is now such that a full day of riding is perfectly doable. Meanwhile, new on-board digital screens and controllers ensure you can track your range and make decisions accordingly.

Range varies depending on the battery size and power consumption. Generally, the less reliance you have on pedal assistance, the greater the range. But, if you are prudent, many modern batteries can last beyond 100 miles.

Charging batteries is also easy. For most modern electric bikes, it’s simple case of popping the battery out of its housing, and plugging it into the mains for a few hours.

On some commuter bikes, batteries are found in rear racks, but in most pedal assist bikes they are mounted to the downtube. Increasingly, batteries are being incorporated into the frame design itself.

When choosing an e-bike, the battery is a big consideration. Here is a quick guide to the technical jargon you’ll come across:

• Watt hours – How much energy a motor can consume. Calculated by multiplying amp hours (volume of power used) by volts (flow rate of power). To understand watt hours, picture a water wheel. You can spin this wheel by firing high volumes of water at it like a fire hose (high amp hours), or, you can have high pressure (high voltage) which also spins the wheel at the same rate, a bit like a pressure washer. Both lead to the same output of moving the wheel (X watt hours).
• Amp hours – The amount of time a battery will stay powered. Higher amp hours equal longer range. Amp hours just measure how much charge passes a point over so much time.
• Volts – How much pressure a battery can contain. Pressure directly effects power, thus, how fast the motor rotates a bikes wheel. High volts mean higher power. Less volts mean the motor will have to work harder to pull you along, putting it under strain. Be smart about how much power you need and how reliant you’re going to be on the motor.

Pros and cons of electric bikes - should you get an electric bike?

As electric bikes grow in popularity, now is the time to consider one for your next two-wheeled steed. To help you navigate that choice, here are some quick pointers to help your decision making process.

Electric bikes are lowering the barriers for cycling as a sport and as a lifestyle.

It has created a more sustainable alternative to commuting by car and made bike commuting more accessible to many.

For others, it has ignited a new love for cycling, whether on the trails, in the streets or on the long and winding roads.

The extended range and speed at lower effort levels is undeniably impressive. This means you can climb higher and ride further than with a traditional bike.

While some bemoan the battery boost, even cycling purists can’t deny that e-bikes are incredibly fun and present new opportunities to those who just want to ride.