25.10.2022 | Reading time - 12 min(s)

How do Electric Bikes work?

Written by Edinburgh Bicycle Cooperative

As e-bikes become ever more popular, people are becoming familiar with the basics of electric bikes but in this article, we will discuss some aspects of choosing an e-bike that are often forgotten about that make a big difference to the performance of the bike. To start with, we will have a quick recap of these basics of buying an e bike and then, we will discuss what difference battery position, motor position, gearing and brakes make to an electric bike.

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Basics recap

Battery power is measured in w/h (watt/hours) and is an indicator of the range of the electric bike with approximately 100w/h equating to 10 miles of range. Electric bike Motor power is measured in n/m (Newton/Metres) and the higher the number, the more torque the motor offers and the easier the bike will power you up hills. The maximum speed you can be assisted to is 15.5mph or 25kmph and all electric bikes sold in the UK, to abide by UK law, will be a pedal assist bike. There are a number of other factors that will affect the feel and performance of electric bikes which we will discuss now.

electric bike MOTOR POSITION

On modern electric bikes, you have 3 different positions that the electric bike motors can go – Front hub, rear hub and centre driven motors and each motor system will give a different feel and affect how much power the motor delivers. The pro's of each will be discussed below.

Front Hub

Front driven hubs are relatively inexpensive and give you a good amount of power up hills. Good for tarmac rides on a budget and the initial acceleration is sufficient to get you away from lights or from a standing start.

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Rear Hub

Rear hub driven motors are also relatively inexpensive, give good acceleration and are more for flat tarmac rides as there is a lot of weight towards the rear of the bike.

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Centre driven

Most e-bikes over a certain price come with a centre driven electric motor, or mid drive motor, as this provides the most natural feel, a better balanced bike (weight towards the centre of the bike) and a higher power output, increasing how much assistance is provided on steep hills. They are also the more reliable bike motor systems. The amount of power provided will depend on the motor type such as Bosch performance line, Bosch active line or the Shimano Steps systems.

e bikes BATTERY POSITION

Often overlooked is what effect the battery position has on the bike. The main positions are: above the rear wheel, on the bike's downtube or integrated into the bike's downtube.

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Rack mounted

Commonly found on lower budget e-bikes as the main body of the frame doesn't need to be reinforced to facilitate the battery. The weight distribution on these bikes is further back and higher. Electric bikes with a rear rack mounted battery are great for leisurely rides on fairly flat terrain.

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On the downtube

Similar to a centre driven motor, the downtube mounted battery moves the weight to the centre and makes for a more balanced bike which is noticeable when cornering and/or travelling uphill.

Integrated

Aside from being more balanced due to the centre of gravity, an integrated battery moves the weight lower on the bike to aid handling and climbing and a lot of people prefer the looks of an interated battery. Most integrated batteries can still be removed from the frame for charging indoors. You will normally find these type of batteries on electric mountain bikes (e MTB) as there is a premium of responsive handling when you are flying downhill.

Gearing

The choice of gearing comes into two broad categories – internal gears or external (derailleur) gearing. Both give different benefits.

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Internal gears

As all of the gears are internal, there is a lot less maintenance or replacement parts required over the life of the bicycle. Because this is a more complex rear wheel, it can be a little more tricky to remove the rear wheel of the bicycle.

External gears

These are the gears that more people are used to, external gears (or derailleur gears) provide a wide range of gears and it is simpler to remove the rear wheel in case of punctures. The thing to watch out for involves the extra torque going through the cassette and chain on an electric bike. Because of this, chains and cassettes can wear out faster if you shift gears under load.

Brakes

On most e-bikes you will have the choice between classic rim brakes or disc brakes (hydraulic or mechanical) and there are big differences between each.

Rim brakes

Usually found on less expensive entry level e-bikes and will provide good stopping power on dry days and flat routes

Mechanical disc brakes

Disc brakes controlled by cable which give better stopping power than rim brakes particularly in wet conditions. As these are controlled by cable and not hydraulics, they can be a bit more effort to pull

Hydraulic disc brakes

Offering the best stopping power in all conditions and very little effort to pull. As most modern e-bikes are in the region of 25kg, it is definitely worth considering hydraulic disc brakes as they will vastly reduce stopping distance. Hydraulic disc brakes are a must, though, on Electric Mountain bikes (e MTB) as their sensitivity and stopping power is essential.

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Tagged: ebike, electric bike

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How do Electric Bikes work?

shop all electric bikes

We also have a number of E Bikes on sale

Basics recap

electric bike MOTOR POSITION

e bikes BATTERY POSITION

Gearing

Brakes

See all our E-bikes here