In a friction drive motor, a small, solid wheel rotates against the side of the tire in order to drive it. The first motorcycles used the same concept, with a motor mounted above the front wheel. The problem is that the drive rubs at the side of the tire. It's inefficient, and it quickly wears the sidewall away. Tires need to be replaced every couple hundred miles. For this reason, you'll seldom see electric bikes with this type of drive anymore.

E-bikes can boost bike usage, offer health benefits and use “an order of magnitude less carbon dioxide than a car traveling the same distance,” according to a 2016 research review published in the journal Transport Reviews.  In fact, access to an e-bike increased cycling trips and distances traveled – and nearly doubled the bike as a mode of transportation, observed one Norwegian study.
Speaking of which, if you're used to non-electric cycles, be aware that e-bikes are heavy and capped at 25kph or 15.5mph. In many cases, that means the bike starts to feel like its actively fighting against you, if you try to push the speed higher than that by pedalling. That's especially true with heavier bikes, for obvious reasons, and can take a while to get used to. 
This thing is also kitted out with a full SRAM groupset, RockShox Yari RC front shocks, Custom Fox Float suspension at the rear and enormously punchy SRAM disc brakes at the front and rear. Fundamentally, it's a mighty off-road machine with pro-spec kit that introduces a new style of trail riding, allowing adrenaline junkies to ride further, climb harder and descend faster than ever before.
We rode the Vado through the gauntlet, including some of the steepest hills in Palo Alto, and it easily handled everything we threw at it, maintaining a steady 20 miles per hour even on the most daunting of ascents. The bike also handles well on downhills and is both nimble and quick on city streets and paved trails. It’s even comfortable to ride for extended distances, which is vitally important for any bike built for urban settings.
The first functioning electric motor was displayed in the early 19th century, though the device constructed by British scientist Michael Faraday did little more than swirl a wire around a magnet when an electric charge was introduced. Still, the concept proved that electricity could do work. Functional electric motors would follow in many forms after that achievement in 1821. Soon scientists and tinkerers around the world, including visionaries such as Nikola Tesla, were experimenting with all manner of electric motors -- some worked with DC power, others with AC. By the end of the century, myriad electric motors had been produced, capable of exerting enough force with enough reliable control that they were practical for use in myriad applications.
If you’ve got the cash and want to get into ebikes, don’t buy this Rattan. My best advice if you have the money is buy a bike store bike with a Bosch/Brose/Yamaha/Shimano drivetrain. We review lots of them here but I’m currently riding a $2000 Raleigh. If you only have around $1,000+ to spend, head to Luna/Rad/Sondors or at least something from a company you’ve heard of with a Bafang motor.
E-bikes mostly use motors and battery options from a few major suppliers: Bosch, Yamaha, Shimano, and Brose. A few other brands exist, but are less reliable or powerful. Some, like the Yamaha system, have more torque, and others, like Bosch’s Active Line, are nearly silent. But, generally, all four make good options. Look for motor output (in torque), which will give you an idea of total power. Just like car engines, more torque equals more power off the line and more boost to your pedaling. But watt hours (Wh) is perhaps a more important figure to use—it takes into account battery output and life to give a more accurate reflection of power (higher Wh equals bigger range).

An itinerant wordsmith with a broad constellation of interests, Lydia Chipman has turned iconoclasm into a livelihood of sorts. Bearing the scars and stripes of an uncommon diversity of experience -- with the notable exceptions of joining a religious order or becoming an artist -- she still can’t resist the temptation to learn something new. Lydia holds a master of arts in English from Georgia Southern University, and a bachelor of arts cum laude in integrative studies from Clayton College. Her expertise is in the areas of robotics, electronics, toys, and outdoors and computer equipment.
The Bosch Performance CX is still one of the most popular motors on the market. It’s synonymous with reliability, but it’s getting on in years. The newly presented Active Line looks like a glimpse into Bosch’s future: it is more compact, lighter, has less internal resistance, and uses a large chainring. It can only be a matter of time before Bosch releases a new performance motor.
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