Adding electric assistance to an existing bike is cheaper than buying a brand new e-bike – especially if you get the conversion kit through Cyclescheme

Most employers who offer Cyclescheme have lifted the £1,000 spending limit for staff, making e-bikes more affordable than ever. But even bigger savings are possible by adding electric assistance to a bike you already own. The bike itself is paid for so you’re only buying the electrical components, such as the motor, battery and controls. Like complete e-bikes, e-bike kits are available through Cyclescheme.

There are three popular types of e-bike kit: front hub motor (front drive); rear hub motor (rear drive); and crank motor (mid-drive). Hub motors are built into a new front or rear wheel, while crank motors fit to the bottom bracket and replace the chainset. All come with big batteries, sensors, cabling and controls. Some have their own app, enabling you to use your phone as a display or control unit.

Motor pros and cons

Front drive is the simplest setup because the bicycle’s drivetrain is untouched. The weight of the motor is more noticeable in the front wheel, however, and traction can be issue when climbing the steepest hills because the front wheel is more lightly loaded by the rider. Front drives nevertheless provide the boost you’d expect from any e-bike motor, and the kits can be very lightweight.

Rear drive and mid-drive motors both apply power to the rear wheel, which is what you expect on a bike, but they do so in different ways. A mid motor benefits from the bike’s gears in a similar manner to your legs, in that it can spin more efficiently. A rear motor operates independently of the gears, like a front-drive, so has to work harder when the wheels are turning slowly – uphill, for example. This is less efficient.

A mid-drive puts the motor weight in the optimum position for balance: low down and central. Mid-drives are more likely to come with torque sensors rather than cadence sensors. This means the motor kicks in when you’re pressing on the pedals rather than spinning them – an advantage when starting off, especially for uphill starts. However, mid-drives are usually more expensive and put additional strain on the bike’s drivetrain so you’ll likely wear out more chains, cassettes and chainrings.

Legal and safety issues

E-bike conversion kits are designed to fit onto existing bikes rather than in them. The battery will literally be bolted on rather than hidden in the frame. Cables will run externally between battery, motor, sensors and controls, with connectors and often cable-ties visible. Aesthetically, it won’t look as neatly integrated as an off-the-peg e-bike. Yet it will function the same.

An e-bike conversion kit has to function like a complete e-bike for legal reasons. In the UK, that means the motor is limited to 250 Watts and must cut out at 15.5mph. Aside from a low-speed walk-assist mode to help when it’s being pushed along, an e-bike must be pedalled to provide electric assistance.

So what about those e-bike conversions you’ve seen buzzing around town at 25mph with the rider not even pedalling? They’re illegal. It’s not against the law to sell or buy faster or powerful e-bike conversion kits. In fact, they’re readily available online from the likes of Amazon and eBay.

It’s a bad idea to buy any of these kits, primarily because in the UK they don’t meet the legal definition of what constitutes an electrically-assisted pedal cycle. So you can’t legally use them. But there’s another important reason as well: fire safety. E-bike batteries can be dangerous unless you buy good quality batteries and chargers from a reputable supplier. You need the right charger, the right battery and a battery management system that prevents overcharging (which can cook the battery) or over-discharging (which can damage the battery cells and cause overheating). Do an internet search for ‘e-bike fire’ if you need convincing that anonymous online conversion kits are a bad idea.

Buying your kit

You can get your (safe, good quality!) e-bike conversion kit through Cyclescheme in one of two ways: direct from the manufacturer if they’re registered with Cyclescheme, such as ARCC or Cytronex; or from a Cyclescheme-registered retailer that stocks conversion kits. That might be a bricks-and-mortar bike e-bike shop or it could be an online retailer specialising in e-bike kits, such as Electric Bike Conversions.

The supplier of your e-bike kit will be able to advise whether or not your bike is suitable for conversion. They may also be able to fit it for you for a fee. If you’re not a confident bike mechanic, this is strongly advised. Fitting a conversion kit isn’t rocket science – especially a front-drive one – but it’s comparable to, say, fitting a new derailleur to your bike. (If you can do that, you’ll be fine.)

 Here’s a list of some of the better-known and better-rated e-bike kits available.

ARCC. Cyclescheme registered. Cambridge-based manufacturer of lightweight (3.9kg) front drive systems. Often fitted to small wheelers (Brompton, Moulton, Airnimal), it can be retrofitted to any suitable bike. Priced from £1,900, including fitting and delivery.

Bafang. Bafang is a large global retailer of e-bike components and kits, which makes front, rear and mid-drive systems. Expect to pay from about £1,000 for a mid-drive, plus any fitting fee.

Boost. Rear drive kit, available as individual parts or built into a rear wheel with all the components you need – which costs £650. Installation is DIY unless you get a Boost retailer to do it for you.

CYC Motors. Mountain bike-oriented mid drives that are, in general, too powerful for use on the road in the UK. But there’s also a road-legal 250W Photon model that costs around £1,000.

Cyclotricity. Inexpensive front, rear and mid-drive kits, costing from around £240, £275 and £420 respectively. Don’t forget to factor in fitting if you won’t be doing that.

Cytronex. Cyclescheme registered. Another lightweight (3.2-3.6kg) front drive system from a UK company. It can be configured to fit most bikes, including Bromptons. From around £1,100, including the charger. Installation costs £155 if you don’t go the DIY route.

Pendix. Elegant mid drive with good torque (65Nm), a range of battery sizes and a useful app. There are versions to fit most standard bikes, generic folders and Bromptons. From £1,700 (not including installation).

Swytch. Like the ARCC and Cytronex systems, this is a lightweight front drive. The battery (there’s a choice of two) is particularly light but that also means less capacity so it suits shorter trips best. From around £500 if pre-ordered.