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The Brompton folding bicycle was first developed in the 1970s, and has changed remarkably little in its lifetime, indicating the strength of the original design. What has changed in the past forty-odd years is that the Brompton has gone from being an [almost] one-size-fits-all product, to being available in a whole range of configurations (including being able to choose between gear ratios and between three different styles of tyre!). But in essence, the fundamentals of a Brompton bike made today are pretty much the same as the original version.


The Brompton Electric
The Brompton bicycle: "a magic carpet you can keep in your pocket" (Quote from Andrew Ritchie, Brompton inventor, in an article written for The Guardian)

However, a big development is on the horizon for Brompton. For years, Brompton have been developing an electric-assist version of their folding bicycle. Not much has been revealed to date about what the final product may be like and its development has very much been kept under wraps. We do know that an electric Brompton model has been a long time coming (it is nearly a decade since the first electric Brompton prototype) and that the development of the electric Brompton bike has been fraught with a series of “immovable technical problems”.1

After working to develop the electric-assist system for the Brompton in Taiwan for three years without the progress that had been hoped for, Brompton partnered up with Williams Advanced Engineering.2 Williams Advanced Engineering is an arm of the Williams Formula One Company which provides cutting edge technology and engineering services, taking advantage of the knowledge and expertise gained from working in the F1 environment. Since this partnership has been formed, the future of the electric Brompton bicycle has been looking brighter, and it may even be ready sometime this year according to Will Butler-Adams, CEO of Brompton Bicycles Ltd.3

The electric Brompton is being developed in partnership with Williams Advanced Engineering, an arm of the Williams Formula One Company
The electric Brompton is being developed in partnership with Williams Advanced Engineering, an arm of the Williams Formula One Company (Image: Williams F1

In terms of the design of the electric Brompton bike, we know that it is expected to use regenerative braking technology, or “kinetic energy recovery system technology”.4 Regenerative braking technology recaptures energy which would otherwise be wasted when braking, and stores it for use later. Regenerative braking already exists on some electric bikes on the market (for example both Trek and Specialized have released electric bikes which use regenerative braking) and is becoming relatively common on high-end electric bikes which use direct drive hub motors.5 Based on information about existing regenerative braking systems,6 it seems likely that the electric Brompton will use a direct drive motor in the front hub. This is also the system that has been used on electric conversion kits produced for the Brompton, such as those made by Grin Technologies,7 and nycewheels.8

We also know that the electric Brompton bicycle will be a pedelec,9 meaning that the electric assistance will only kick in when the rider is pedalling and will cut out when the rider stops pedalling (the alternative is the ‘throttle’ design, which can be used to provide assistance even when you are not pedalling, as long as maximum speed at which you are assisted is no more than 15.5mph and that the bike does have pedals to propel it).10 Advantages of the pedelec system as opposed to the throttle system are that it only provides assistance when needed and so is more efficient, and doesn’t require you to hold down a throttle or activate the electric assist yourself, as a sensor in the pedals senses when assistance is required and the motor then comes on automatically.

The pedelec system
The pedelec system will only kick in when the rider starts pedalling (Image: Brompton website)

In terms of where the battery to power the system will be fitted to the Brompton bicycle, nothing has been indicated by Brompton or Williams to date. Existing electric Brompton conversion kits locate the battery pack in a range of places on the Brompton, from using a rear rack battery mounted to the seatpost,11 to a mounting on the main frame, to locating the battery inside a Brompton front bag attached to the bike with Brompton’s own carrier block system.12 This latter option seems like the neatest solution of these conversion systems as it does not affect the fold or change the overall profile of the bike. Given Brompton’s general meticulousness, we foresee a solution where the battery will seamlessly, unintrusively connect with the motor in a way that is unaffected by the fold. Given that we don’t yet know whether the motor will be sited in the cranks or the hub this connection could be achieved in a range of ways.

So what does all this mean for existing and potential Brompton bike owners? We know that there is already a market for electric Bromptons, since there are already several electric conversion kits for Brompton bikes available on the market (although fitting these non-Brompton kits will void the Brompton’s warranty). Brompton are generally very good at making any new developments retrofittable and so it is likely that any existing Brompton owners may be able to take advantage of the electric system by upgrading their existing bike, for example by swapping out the front wheel for a motorised wheel (if this is how the system works) and adding the battery pack, connections etc.

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The Brompton is an 'urban transport solution' rather than 'just a bike' for many owners
The Brompton is an 'urban transport solution' rather than 'just a bike' for many owners (Image: Brompton website)

The Brompton is known for being a bike that is ‘not just for cyclists’, with a very small proportion of its market “mad-keen cyclists” and a far greater proportion of Brompton owners using the nifty bikes because of the ‘urban transport solutions’ they offer, rather than because they are ‘cyclists’.13 It is hoped that the electric Brompton will offer a means to remove the perceived connection between cycling and “sweat and lycra” which presents a barrier to everyday cycling for many people.14 This could especially be the case in countries like the UK which have less of an everyday cycling culture, or in places where perspiring whilst cycling is more likely or unavoidable due to hot climate, hilly terrain or feeling like you need to cycle hard and fast to keep up with other traffic in certain road conditions.

On this basis, the electric Brompton bike could become the Holy Grail of urban cycling, although we can't say for sure when it will be available - all we can say is we can’t wait for it to arrive on the urban cycle scene soon!


Brompton has released full details of what will be called the Brompton Electric, and announced an early 2018 release date. More info here.

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About the Rider: Anne
Anne’s unique selling points are her super-strong thumbs (a hangover from her days fitting Marathon Plus tyres) and her enthusiasm for cake (both baking and eating). When not sorting out returns, writing for the website or delving into complex customer questions, you’ll find her fixing up friends’ bikes or enjoying the ride.
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