Look at a contour map of the Sefton coast and you will struggle to find anything worth calling a hill. For most bikes that is pleasant. For an electric conversion it changes the whole shopping list, because nearly every decision about motors and batteries comes back to one question: how much climbing will this bike actually do?
On a flat commute the answer is “very little”, and that opens up a cheaper, lighter and simpler way of electrifying the bike already sitting in the hallway. Here is how a flat route reshapes the choices, and where the real work goes instead.
The wind is your hill
Riders in hilly towns plan around gradients. On the coast, the enemy is air. A steady breeze off the sea can cost as much effort as a long drag uphill, and unlike a hill it does not end at the top. Ride out along the front into a south-westerly and back again, and one half of the trip is a gentle cruise while the other feels like pedalling through porridge.
This matters because wind loads a motor differently from a slope. A climb asks for a burst of torque at low speed. A headwind asks for moderate, continuous power at normal riding speed for as long as the wind blows. The good news is that this is exactly the sort of work a modest motor handles comfortably. You do not need the punch of a big mid-drive to hold 14 or 15 mph into a breeze; you need a motor that can deliver a steady few hundred watts without getting hot, and a battery that does not mind giving it.
Body position helps more than most people expect. Dropping the elbows and tucking in slightly on exposed stretches reduces drag noticeably, and the battery gauge will thank you for it.
Why a hub motor makes sense on the flat
There are two broad ways to convert a bicycle. A mid-drive motor sits at the cranks and drives the chain, so it can use the bike’s gears to multiply torque. That is a big advantage on steep ground. A hub motor lives inside the wheel and turns it directly, independent of the gears.
On a flat route, the mid-drive’s gearing advantage barely gets used. Meanwhile the hub motor brings its own benefits. It puts no extra load through the chain, cassette and chainring, so those parts wear at roughly the rate they would on a normal bike. It is mechanically simple to fit: in most cases the old wheel comes out, the motor wheel goes in, and the rest is cable routing and mounting. And if the chain snaps on the way to work, a hub-driven bike can still limp home on the throttle.
A rear hub motor kit is usually the better pick for commuting. A rear motor keeps traction where the rider’s weight sits, behaves well on wet tarmac and puts less stress on the front fork and dropouts. Front hubs are lighter and easier still to fit, but they can feel a little skittish on slippery surfaces and suit lighter use better.
Geared or direct drive?
Hub motors come in two flavours. Geared hubs contain a small planetary gearbox, which makes them compact, light and lively from a standstill, and lets them freewheel without drag when the power is off. Direct-drive hubs have no gears at all; they are heavier and larger, but almost silent and extremely durable, and they shrug off sustained running at speed.
For short town hops with lots of junctions and lights, a geared hub feels nippier. For long, steady coastal runs where the bike spends most of its time at cruising speed, a direct-drive hub is very happy. Either works; it comes down to how stop-start your journey is.
You can probably buy a smaller battery
The battery is the most expensive part of any conversion, and this is where a flat commute saves real money.
Energy use on an e-bike depends heavily on terrain. Climbing burns through watt-hours fast because the motor is lifting the weight of bike and rider against gravity. On level ground most of the energy goes into overcoming rolling resistance and air, which at commuting speeds is far less demanding. A rider who uses the motor as assistance, pedalling steadily alongside it, might use somewhere in the region of 8 to 12 watt-hours per mile on the flat in mild weather. Lean on the throttle without pedalling and that figure rises sharply.
Work it out for your own trip. Take the round-trip distance, multiply by a cautious 15 watt-hours per mile to cover wind and winter, then add a margin of around 30 per cent so you are not running the pack flat every day. Lithium cells last longer when they are not routinely drained to empty, so that margin is not wasted; it pays you back in battery life.
For an eight-mile round trip, that sum points to something like 160 watt-hours of genuine need, which almost any conversion pack covers several times over. The practical upshot is that a flat-route commuter can often choose a compact pack, charge it two or three times a week rather than every night, and still have plenty in reserve.
The things that actually wear out by the sea
If the terrain is kind to motors, the coastal air is less kind to everything else. Salt carried on the breeze settles on metal and holds moisture against it. On a bike that lives outdoors, this shows up as fast-rusting chains, seized bolts and, on an electric bike, corroded connectors.
A few habits keep a converted bike out of trouble:
- Give it a fresh-water rinse every week or two. A gentle spray or a bucket and sponge is enough. Avoid pressure washers near the motor, bottom bracket and connectors, because they force water past seals.
- Keep the chain lubricated with a wet-weather lube and wipe off the excess. A dry chain on a coastal bike can turn orange in a fortnight.
- Treat the electrical connectors. A small dab of dielectric grease on the pins of the motor, display and throttle plugs keeps moisture out and makes them easier to separate later.
- Check the drip loops. Cables should dip below each connector before rising into it, so water runs off the low point rather than into the plug.
- Bring the battery indoors. It charges more safely at room temperature, it lasts longer, and it is less tempting to thieves.
Windblown sand is the other coastal quirk. After a blustery day the coast road can carry a fine grit that finds its way into brake pads and chains. A quick wipe of the rims or discs and a squeeze of the brakes before riding off clears most of it.
Brakes, lights and tyres before the motor
Adding a motor adds weight and makes higher average speeds effortless, so the parts that keep you safe need to be up to it.
Start with the brakes. Rim brakes on an old hybrid can cope with a light conversion on the flat, but fresh pads and properly tensioned cables are non-negotiable. If the bike has mechanical disc brakes, check the rotors are not worn thin. Many conversion kits include brake levers with cut-off switches that stop the motor the instant you pull them; fit them, because they turn an emergency stop from a tug of war into a clean halt.
Lighting comes next. With dark mornings and evenings for half the year, a commuter needs proper front and rear lights. Some displays and controllers can power lights directly from the main battery, which removes the nightly ritual of charging separate units.
Finally, tyres. Puncture-resistant commuter tyres in a slightly wider size smooth out patched road surfaces and cut down on roadside repairs. Fixing a flat on a hub motor wheel is more involved than on a standard wheel, since the motor cable has to be disconnected and the axle nuts are tighter, so preventing punctures is worth paying for.
Fitting it yourself, or not
A hub motor conversion is within reach of anyone comfortable swapping a wheel, adjusting brakes and using a set of spanners. The physical work is a few hours on a dry afternoon. The parts that trip people up are rarely mechanical.
The first is compatibility. Before ordering anything, measure the gap between the rear dropouts, note whether the bike uses a freewheel or a cassette, and check the brake type, since a hub motor wheel needs to match all three. Disc brake bikes need a motor with a rotor mount; rim brake bikes need a rim of the same diameter as the old one so the pads line up.
The second is the axle. A hub motor pushes against the frame through its axle, and on aluminium frames or thinner dropouts a torque arm is cheap insurance against the axle spinning in the slot. It takes ten minutes to fit and prevents one of the few genuinely expensive mistakes in a conversion.
The third is cable management. A conversion adds a motor cable, a throttle, a display, brake sensor leads and sometimes a pedal sensor. Run them neatly along the frame with cable ties, leave enough slack at the handlebars for full steering lock, and keep them away from the moving chain and the front wheel. Tidy wiring is not just about looks; it is what stops a connector being yanked loose when the bike is wheeled into a rack.
If any of that sounds like more than you want to take on, a workshop can fit a kit in a morning and check everything over before handing it back. Many riders do the shopping themselves and leave the final wiring and set-up to someone who does it every week.
A charging routine for the working week
On a flat route with a sensibly sized battery, charging becomes something you do two or three times a week rather than every night. A few habits make that routine kinder to the pack.
Charge indoors, on a hard surface, away from the front door and anything flammable, and unplug once the charger shows full rather than leaving it connected for days. If the bike will be parked for a week or two over a holiday, leave the pack around half full rather than topped up or empty. And stick with the charger that came with the battery or one specified for it; a mismatched charger is one of the quickest ways to shorten a pack’s life.
Riders who commute only a few miles each way often find that charging on a Sunday evening and again mid-week covers everything, with enough left over for a weekend ride along the coast.
The money side
Whether a conversion makes financial sense depends on what it replaces. Against the running costs of a second car, the sums are rarely close. A full charge of a typical e-bike battery uses less than one kilowatt-hour of electricity, which at household rates at the time of writing works out at well under a pound, and on a flat route that charge can last several days of commuting.
Against buying a new electric bike, a conversion saves most when you already own a decent frame with sound wheels, brakes and gears. Converting a comfortable bike you know and trust also means you keep its fit, which many riders value more than they expect. Where the base bike is tired, with a cracked frame, worn-out gears or rusted components, the savings shrink, and it is worth pricing up the repairs honestly before committing.
A flat town rewards a simple build
The temptation with any e-bike project is to buy the most powerful motor and the biggest battery on the shelf. On a coast with no real climbs, that is money spent on capability you will rarely use, plus extra weight to carry every time the bike goes up the front steps. A modest hub motor, a sensibly sized battery and a bike that has been properly prepared for salt and rain will cover years of commuting with very little fuss.
At All4eBikes, the first thing we ask anyone planning a conversion is what their route looks like, because the right build for a coastal commuter and the right build for someone tackling the Welsh valleys are very different machines. If you can describe your journey, the distance, the wind and how often you will charge, you are most of the way to choosing the parts.
George Andrusca is the founder of All4eBikes, a senior mechanic and electrical engineer who builds and repairs electric bike conversions in Cardiff.