A folding bike with the EZ Rider front hub fitted. The rear hub gears stay exactly as they were.
Alt text: Folding bike fitted with the EZ Rider silver front hub motor and handlebar battery unit
Yes. A classic 16-inch Brompton can take an electric front-hub kit and stay a legal pedal cycle in Great Britain, provided the kit is built for it. The catch is the fork: a Brompton’s front dropouts are 74 mm apart, not the 100 mm of a normal bike, so a standard front motor will not fit without forcing the fork, and forcing the fork is never the answer.
Get a kit made for that 74 mm spacing and the rest is about keeping what makes a Brompton worth owning: a fold that still works, a weight you can still lift onto a train, and enough battery for your commute without carrying a brick you do not need.
Key takeaways
- A classic 16-inch Brompton can take a 250W front-hub conversion and remain a legal electrically assisted pedal cycle in Great Britain.
- The fork is the fit question: Brompton front dropouts are 74 mm apart, so the kit must use a 74 mm hub and a 349 mm bead-seat rim.
- The G Line uses 20-inch wheels and a different fork, so 16-inch kits do not apply to it.
- Check all three positions, riding, part-folded and folded, with your usual bag fitted.
- Choose the battery for your route: a 12-mile round trip needs roughly 225 Wh with a reserve, not the biggest pack available.
Brompton electric conversion kit: check which Brompton you have
Brompton now makes more than one wheel size. The classic models, including the C Line and A Line, use 16-inch wheels. The G Line uses 20-inch wheels and a different fork, so a 16-inch conversion does not apply to it. Bromptons that left the factory as Brompton Electric already have their own system.
Read the tyre sidewall. A classic Brompton tyre is marked 16 × 1â…œ and carries the ETRTO size 35-349 or similar. That 349 figure is the bead-seat diameter, and it is the number that has to match the replacement wheel, not the “16-inch” label.
The 74 mm front hub is the whole fit question
The EZ Rider Brompton kit: a silver 74 mm front hub, two LG-cell packs, display and charger.
Alt text: KirbEbike EZ Rider Brompton kit: silver 74 mm front hub wheel, two batteries, display and charger
The EZ Rider Brompton conversion option is built around exactly this. It uses a 36V 250W geared front hub with 74 mm spacing, laced into a 16 × 1â…œ-inch wheel, with a 36V 14A FOC controller and a colour display. The Brompton motor wheel is silver, so it looks at home on the bike. The kit’s universal version uses normal spacing for full-size bikes, so make sure you order the Brompton model.
When it arrives, check three things before you ride:
- The axle seats fully in both dropouts, with the supplied washers in the right order.
- The rim brake lines up with the new rim, and the pads hit the braking surface, not the tyre.
- The tyre clears the fork crown and the mudguard all the way round.
Do not spread the fork to take a wider hub, whatever material it is made of. If the hub does not drop in, the kit is wrong for the bike.
Fitting it: what the job involves
KirbEbike describes the EZ Rider as a roughly 20-minute install for someone comfortable with basic tools. On a Brompton the order is:
- Remove the front wheel and keep it, with its axle nuts and washers.
- Check the tyre on the new motor wheel, and move your own tyre across if you prefer it.
- Drop the motor wheel into the 74 mm dropouts with the cable exit facing the way the instructions show, then fit the washers and tighten the nuts.
- Adjust the front brake to the new rim.
- Mount the battery and display unit on the handlebar, and fit the pedal sensor and any brake sensors the kit includes.
- Route the motor cable along the fork leg and brake cable, leaving slack at the hinge, and secure it with ties.
- Fold and unfold slowly three times before the first ride.
If the axle will not seat without force, stop. That is a fit problem, not a tightening problem.
Make sure it still folds
A Brompton is three bikes in one: riding, part-folded and fully folded. The conversion has to work in all three positions. A cable that looks neat on the road can be trapped by the handlebar hinge or stretched when the front wheel tucks in.
Route the motor cable along the fork leg and the brake cable, follow the kit’s routing guide, and then fold slowly while you watch:
- The handlebar stem as it folds down, and the cables at the hinge.
- The front wheel as it swings across, and the motor cable around the hook.
- The parked fold, to check nothing electrical is carrying the bike’s weight.
Repeat it with the bag or light you normally carry. A fold that works without the front bag and jams with it is a problem you want to find at home, not on a platform.
Route the motor cable along the fork and check it at every hinge before you trust the fold.
Alt text: Converted folding bike with the EZ Rider kit, parked beside a park pavilion
Work out what you will actually lift
Brompton owners carry their bikes, so weight matters more than on any other conversion. The right sum is the weight of the bike, minus the front wheel you remove, plus everything you add: the motor wheel, the batteries, the controller, the display and the wiring.
KirbEbike quotes 6.0 kg for the EZ Rider kit with both batteries. A classic Brompton weighs roughly 11–13 kg depending on model and gearing, and you remove its front wheel, so a converted bike typically lands in the mid-to-high teens before luggage. Try lifting a bag of that weight up a flight of stairs before you decide; that is the honest test.
Because the battery is separate, you can split the load: carry the bike in one hand and the battery in a bag. It is one more thing to carry, but it makes stairs and luggage racks easier.
Choose the battery for the commute, not the brochure
The EZ Rider kit comes with two LG-cell packs: 36V 7Ah and 36V 15Ah. In watt-hours, that is about 252 Wh and 540 Wh, or 792 Wh together.
Work out your own need. A 12-mile round trip at a gentle 15 Wh per mile uses 180 Wh. Keep a 20% reserve and you want about 225 Wh. The small pack covers that, with not much to spare on a cold morning or into a headwind. The large pack covers it comfortably, and both together cover a long weekend ride.
So a daily commuter on a short, flat route might carry only the small pack and save the weight. Someone with hills, a longer ride or no charging at work takes the large one. Use the packs the way the kit’s instructions describe; do not join them with an improvised splitter. The supplied 4A charger refills the packs faster than the 2A chargers many kits ship with.
How a front hub feels on a 16-inch wheel
A front-wheel motor pulls the bike rather than pushing it. On dry tarmac you hardly notice. On wet paint, metal drain covers or loose gravel, a small, lightly loaded front wheel can spin if you start in a high assist level with the bars turned, so start in the lowest level and let assistance build.
The small wheel also means the motor turns faster for a given road speed than it would on a full-size bike, which suits a geared hub well: it is working near its efficient speed at commuting pace. You will notice the extra weight on the front when you lift the bike onto a kerb or into the fold. Most riders adjust within a week.
Conversion or a factory Brompton Electric?
Brompton sells its own Brompton Electric, which also uses a front hub motor, with a battery that clips to the front carrier block. It is designed and supported as one system. A conversion keeps the bike you already own, costs considerably less, and lets you choose your battery capacity.
Choose the factory model if you want a single warranty and a dealer network to service it. Choose a conversion if you already own a sound Brompton you like riding, want to spend less, and are happy to fit and maintain a kit yourself or with a local shop.
What it costs to run
Electricity is the cheapest part of an electric Brompton. Charging both EZ Rider packs from empty puts roughly 0.8 kWh into them, plus some charger losses. At a typical UK unit price of around 25p per kWh, that is about 20–25p for a full charge, and most commuters will not use a full charge each day.
The real running costs are the usual Brompton ones, slightly accelerated: tyres and brake blocks wear a little faster with the extra weight and speed, and the front tyre does more work because it now drives the bike. Lithium batteries also age. Expect noticeable capacity loss after several hundred full cycles, and store the packs part-charged in a cool, dry place over winter to slow it down.
Stay inside the 250W rules
In Great Britain, an electrically assisted pedal cycle needs working pedals, a motor with a continuous rated power of no more than 250W, and assistance that stops at 15.5 mph. You must be at least 14 to ride one. If the bike can be propelled up to 15.5 mph without pedalling, as with a twist-and-go throttle, it also needs type approval.
A 250W front hub that assists only while you pedal, and cuts out at 15.5 mph, meets that description. If you add a throttle, keep it to walk-assist speed unless you are prepared to deal with approval. And because the rules are about the motor’s continuous rating, a display setting cannot turn a more powerful motor into a legal one.
Living with it
A front hub leaves the Brompton’s rear hub gears untouched, which is why it suits this bike. It also puts the drive on the steering wheel, so the first few rides feel slightly different, especially on wet paint and drain covers. Start on the lowest assist level and ride somewhere quiet for an afternoon.
Keep the original front wheel. Learn how to remove the motor wheel and fix a front puncture before you need to do it at the roadside. And check the warranty position: Brompton’s frame warranty and the kit supplier’s warranty are separate, so read both before you fit anything.
If you are still deciding between kits, conversion kits with battery options are easiest to compare once you have filtered for your exact folding bike. A cheaper universal kit stops being cheaper the moment it needs a modified fork.
The questions that decide a Brompton conversion
Will any 16-inch front-hub kit fit?
No. It needs 74 mm spacing and a 349 bead-seat rim. A normal 16-inch kit has 100 mm spacing.
Will it still fold?
If the cables are routed as the kit intends, yes. Check all three positions with your usual luggage before you rely on it.
Does a front motor change the gears?
No. The rear hub gears stay as they are, and they still help you pedal up hills.
Is it still road legal?
A 250W pedal-assist front hub with a 15.5 mph cut-off is, for riders aged 14 and over. A throttle that works above walking pace is not, unless the bike is type-approved.
Can I take a converted Brompton on a train?
Most UK train operators accept folded bikes at any time, which is one of the main reasons people choose a Brompton. Some operators set their own rules for e-bikes and batteries, so check the policy for your route before relying on it.
How far will a converted Brompton go?
With both EZ Rider packs (about 792 Wh), KirbEbike quotes 40–60 miles. Your figure depends on the assist level, hills, temperature and how much you pedal. The smaller pack alone suits short daily commutes.
Does a conversion void Brompton’s warranty?
Brompton’s frame warranty and the kit supplier’s warranty are separate. Read Brompton’s current terms before fitting anything, and keep the original front wheel so the bike can be returned to standard.
Sources
- UK Government, “Riding an electric bike: the rules” (gov.uk)
- Brompton, G Line (brompton.com)
