Skarper vs Swytch e-bike conversion kits review

At Top Gear, we are fond of an impressive bit of tech. Last year, we introduced Skarper, a start-up that has worked with Red Bull Advanced Technologies (RBAT). Its product is, in essence, a clip-on unit that converts an ordinary pedal bike into an e-bike. Now we have put it to the test.

We did not test it in isolation, either. Comparing two products helps reveal each one’s strengths and compromises, so we have also spent time with a Swytch system.

Skarper and Swytch e-bike conversion kit designs

Skarper is an elegantly streamlined, single-box system which attaches to and detaches from the rear wheel. The unit houses the battery and drive motor, while the usual rear disc brake is swapped for an ingenious version incorporating a drive hub.

Photography: Luke Marriage

Swytch is rather more complex. Its motor sits in the front wheel, while its battery mounts to the handlebars, meaning several wires need to be routed around the bike. There is also a cable for the optional display, plus another running to the pedal crank, allowing the system to detect when you are pedalling and provide assistance. Skarper instead uses a Bluetooth sensor.

You have probably worked out that Skarper is the more upmarket option. It is priced at £1,495, while a Swytch system costs from £500 to more than £1,000. That wide range exists because Skarper is a one-size-fits-all product, whereas Swytch offers a choice of specifications.

There are three handlebar-mounted battery capacities, known as Max and fitted with integrated ‘be seen’ lights, plus three Go batteries that fit inside the frame. You also need to choose the front wheel suited to your bike, although a rear-wheel option is available too. One quick clarification: the bike in these photographs has considerably more wiring than usual because it has been configured to run every possible system variation. With a little care, you can install it far more neatly than I did.

Weight, power and range

As you are reading about bicycles in Top Gear, let us use some reassuringly familiar numbers. The Skarper unit weighs 4.5kg, while its distinctive disc brake is around 500 grams heavier than a standard disc. That makes for a total weight increase of 5kg.

That disc is the genuinely clever component, incidentally, and why Skarper required RBAT’s engineering and materials expertise. It must transmit substantial torque - 45Nm - through a shaft much slimmer than your little finger. Its energy comes from a 0.24kWh battery.

Swytch claims the Max+ weighs 3.6kg, although that figure is somewhat generous about what a normal front wheel weighs. Its overall weight addition is also roughly 5kg, providing a 0.275kWh battery and a 250W/40Nm motor.

Both systems provide assistance only to the legal limit of 15.5mph (25kmh). As they are effectively hybrids, with electric assistance supplementing another source of power - your legs, here - range is difficult to pin down. This much is true: it always goes further than you expect it to. Skarper claims up to 30 miles, while Swytch quotes 30-40 miles. Once that is exhausted, you are left to pedal - although you are simply riding a bike that weighs 5kg more than normal.

How the Skarper and Swytch systems ride

This is how they perform on the road. Swytch makes the bike two-wheel drive and puts considerable weight at the front. That makes the steering feel heavier, leaves it more vulnerable to being knocked off line by bumps, and can make its behaviour less predictable - you have never experienced torque steer on a bicycle before, have you? It also takes two or three pedal turns before waking up and delivering assistance, so it is not instantly rapid away from traffic lights. Once underway, though, it is exceptionally quiet and smooth. When you park, simply take off the battery and carry it with you. Apart from the additional cabling, the rest of the equipment is difficult to notice: the front wheel merely appears to have an oversized hub.

Skarper makes more noise, with some whine from the rear gear spline, but it is otherwise the more advanced system. It responds and assists more quickly, and supplies its power in a more natural way. It needs to, because Swytch has an optional display through which you can select one of five assistance levels, while Skarper does not. Once you are riding, having chosen Eco, Cruise or Turbo, you cannot alter the setting. An app is currently being developed.

Is that a major problem? Not particularly. Alongside a small Bluetooth accelerometer on the pedal arm, the system includes an inclinometer, enabling it to recognise an uphill stretch and contribute more power to prevent you breaking into a sweat. Your sole additional control is the ability to switch it on or off, done by rotating the pedals backwards three times. The other drawback of this tidy design is that there is no indication of the remaining battery charge.

There are benefits, however. As the weight is carried low down, it does not disturb the bike’s handling in the same way, and the unit can be fitted or removed in two seconds. Literally. Align the locating pins with the holes in the disc, then close the handle to secure it. With Swytch, the battery is the only component removable for security; with Skarper, the rear disc is all that remains on the bike. Nobody is going to spot that.

Likewise, should you wish to ride with no electric help, Swytch will permanently leave you with a few extra kilograms and some additional cables, whereas Skarper will not. Swytch is claimed to work with 99 per cent of bikes, though, while Skarper is compatible only with bikes using disc brakes rather than rim brakes.

The best part? You can cheat. A conventional e-bike must detect real pressure being applied to the pedals before adding its boost. These systems need only sense movement. Put another way, rotate the pedals slower than your road speed and you can fool the motor into continuing to do the work.

With electric cars, there is endless discussion about subsidies and grants that save only a small percentage. Both kits qualify for the cycle-to-work scheme. Swytch is particularly well suited to commuting. It is a genuinely capable and efficient device, able to carry you along at 15mph for a couple of hours. The Max system also includes a built-in light. It is not sufficient to illuminate the road ahead properly, but it does make you easy to see. At your destination, remove the battery and take it inside to charge; it also serves as a USB charger.

Swytch excels as a commuter system. Realistically, you will install it and probably leave it there. Skarper is for riders more serious about cycling who only want assistance occasionally. Have a gravel bike, road bike or touring bike - or simply want the most discreet commuter possible? This is the system to choose.

Skarper costs serious money, but it is one of those superbly considered products that is deeply satisfying to use, makes an excellent conversation piece and shows relentless attention to detail. Instead of being designed around a specific role, it offers an alternative to purchasing a dedicated e-bike. Such bikes cost around £1,500 more than their unassisted equivalent and generally look much more ungainly. Here, you retain your existing, sleeker-looking bike and decide whether you want assistance on any given day. Yes, you can choose to ‘e’ or not to ‘e’.

Scores

Swytch: 8
Skarper: 8