Review: BionX Electric assist

By Karl Rosengarth

BionX of Aurora, Ontario fabricates a variety of electric power systems for bicycles, with 250-, 350- or 500-watt options (and prices ranging from $1,200 to $2,200). The 350-watt, $1,900 PL350HT L is an aftermarket system for adding electric assistance to an existing bicycle. A bike equipped with a BionX system qualifies as a low-speed electric bicycle and is not considered a "motor vehicle," according to National Highway Traffic Safety Administration regulations.

Electrical assistance is provided by a motor built into the hub of the system’s rear wheel. Available wheel sizes include 20", 24", 26" and 700c. The system includes a battery, handlebar-mounted control unit, battery charger, and all the hardware and wire cables required to electrify your bike. It weighs in at 18.4lbs. The control unit’s uncluttered display shows speed, assistance level, battery level and time of day. Our test system came pre-installed on a Trek 6000 mountain bike. However, from reading through the installation instructions, I’d say that anybody comfortable working on their bike could install the system themselves.

There are two basic types of electric power-assisted bicycles: pedelecs and e-bikes. A pedelec only supplies power assistance when the pedals are turning, while an e-bike provides power on demand, typically via a throttle or switch. The BionX system offers both types of assistance.

In pedelec mode, up/down buttons on the PL350HT L step through four available levels of assistance: 35, 75, 150, or 300%. You pedal just like a normal bike, but with a boost that feels like a tailwind or an invisible stoker. To keep the bike from unexpectedly surging forward, the assist does not kick in until the bike is up to 3mph.

I found that assist level 1 provided a helpful boost on flat ground. When faced with rolling hills, I’d bump the assist level up to 2. On steeper terrain, level 3 gave me a significant push up the hills, and was great for "making time." I could easily cruise along at 20mph on rolling terrain, which is the cut-off speed above which the built-in governor circuitry stops providing assistance (for safety/regulatory reasons). Setting #4 made me feel like a superhero. Note that amateur bicycle racers typically average 200 to 300 watts of power generation, so the BionX system is roughly equivalent to having a second person’s worth of power assistance.

The BionX system also has four "generator" settings that use the wheel’s rotational energy to recharge the battery and act as a "drag brake," useful for scrubbing speed on steep downgrades. For safety, a sensor on the right-hand brake lever automatically toggles the system into generator mode whenever the brake lever is actuated.

At the 2010 Interbike trade show, I made a point of riding as many pedelecs as I could get my hands on. My three months on the BionX reinforced my initial impression that BionX-equipped bikes did the best job of smoothly blending pedaling power with electric assistance. Thanks to an intelligent torque sensor in the motor axle, the harder you pedal, the more assistance the system provides. If you pedal lightly, you receive gentle assistance. Stop pedaling and your assistance is automatically cut off. The only time the system felt "herky jerky" was when I was in the big ring and mashing slow, square pedal strokes up a hill. Under those conditions, the assistance felt like it surged along with my output on each downstroke.

The quoted range for the BionX PL350HT L is 56 miles, but your actual mileage will vary, depending on the terrain and how much assistance you dial up. I routinely rode hilly routes in the 10- to 20-mile range using a mix of assist levels 2 and 3, and typically consumed 50%, or at most 75%, of the battery. The rated charge time for an empty battery is five hours, and that jives with my experience that a half-ish drained battery would recharge in two to three hours.

I experimented with the e-bike mode, actuated via a thumb lever, which provided full electric assist. I found out, not surprisingly, that not pedaling drained the battery rather quickly. While the e-bike mode worked well and moved me along at a snappy pace on level or rolling terrain, it slowed down significantly on steep hills. I’d recommend contributing some pedaling effort when pointed uphill. The BionX system is aimed at the pedelec market, so if you’re looking for an "electric scooter" that doesn’t require pedaling, you’ll want to look elsewhere.

The Li-Mn battery on my test bike attached via the water bottle mounts on the downtube. With the flip of a built-in quick release lever, the battery slides off its mounting hardware, for security or for remote charging. The battery also comes with a key and a built-in lock that secures it to the mount, which provides anti-theft protection in lower-risk situations. BionX also offers models with batteries that mount under a rear rack.

The BionX is the smoothest pedelec I’ve ridden to date. The smoothness, simplicity and intuitive nature of the BionX system make it very rider-friendly. If you’d prefer a ready-to-ride option, several U.S. bike brands offer models with the BionX system integrated into their design, Trek and OHM to name two.

The BionX system comes with a two-year warranty, excluding the battery which has a one-year warranty. Visit for more information or to find a BionX dealer near you to score a test ride.


This review appeared in Bicycle Times Issue #9. To read more great reviews and features that you won’t find anywhere else – and help us keep the good stuff coming – consider picking up a subscription today. You’ll get six issues a year delivered right to your door for just $16.95. 



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