Advanced electric bikes
Short review: BionX assist on Dahon Cadenza (Summer 2011)

A first impressions report on the BionX power assist system, in the form of a kit fitted to a Dahon Cadenza full-size folding bike. Read this short review in full.

Posted by Peter Eland on Thursday 6 Oct 2011

This review appeared in Electric Bike magazine Issue 3. Click the viewer below to read the review with the original print layout - or scroll down for the full text and images online!



BionX: the boost which brakes



A first impressions report on the BionX power assist system, in the form of a kit fitted to a Dahon Cadenza full-size folding bike.

BionX review photo copyright Electric Bike Magazine


The BionX power assist system was initially developed in Canada, and immediately gathered a reputation for being really good kit. Unfortunately, for several years manufacturers and consumers alike found supply difficulties frustrating. Now, though, they seem to have sorted that out and in the UK, distribution is in the capable hands of well-established trade supplier Zyro. Kits to fit to an existing bike are available with prices running from £1079.99 to almost £1800.

Zyro sent us a well-used Dahon Cadenza demo bike with a kit already fitted, along with other (not relevant here) upgrades and modifications. It's not obvious, but this bike can be folded in half via hinges hidden in the frame tubes - and having the kit fitted doesn't affect this.
Our kit uses a substantial 37V, 9.6Ah battery pack. You'd best hope you don't need more, as a spare costs an astonishing £1049.99! It's a curvaceous unit fitted to a bracket on the downtube, with a key lock to release. It can also be charged in situ via the XLR socket on the side. The cables to motor and handlebar display unit are led out from the battery mounting bracket (so they stay in place if you remove the battery). There's plenty of heatshrink and insulation to protect the cables as they exit - the rest of their runs to motor and controller are tidied with cable ties.

BionX review photo copyright Electric Bike Magazine
Spare batteries are fearsomely expensive, so take care of the one that comes in the kit!


The whole rear wheel is supplied with the kit (either 700c or 26") and the cable enters the motor on the non-drive side, with a connector hidden below the chainstay under a protective cover. The motor is equipped with a standard disk brake mount, and on the drive side with a mounting for a screw-on freewheel.

BionX review photo copyright Electric Bike Magazine
As you can see here, the rear wheel version of the BionX motor can be fitted with a disk brake. The neoprene sleeve on the chainstay protects the motor cable and connector.


The handlebar console fits on a nice solid bracket, and is quickly removed if necessary. Here you can select the various power assist levels, see speed, distance, charge level etc.

BionX review photo copyright Electric Bike Magazine
The display unit


BionX review photo copyright Electric Bike Magazine
The display is easily removed.


A secondary cable runs from the console bracket to the front brake lever, where a small magnet and sensor allow the brake lever to control one of this system's key features - the regenerative braking function. The idea is to set the sensor so that when you just tweak the lever, it switches the motor from assisting you to acting as a generator and slowing you down, feeding some energy back into the battery as it does so. When it's set up right you can use this effect to slow down without using your normal brakes at all. If that's not sufficient stopping power, just squeeze the lever a bit harder and the brakes engage as normal.

BionX review photo copyright Electric Bike Magazine
Magnet and pick-up on the brake lever let you control the regenerative braking.


So how did it work? Well, it feels like one of the most powerful systems I've tried: after an initial half turn of the pedals, the motor kicks in and at the full assist level, it simply whisks you up to 15 mph smoothly and silently - so quickly in fact that I got into the habit of simply leaving the bike in top gear: nothing else is needed! The power the motor gives is nominally 300% of your effort: in reality this is enough that you rarely need to put in significant work yourself to get the bike up to full speed. At lower power levels it works well with you if you want more of a cycling workout, feeling natural and responsive. And the range seemed really good too: depending on your pedalling effort and all of the other factors, the quoted 50-odd miles doesn't seem unrealistic.

The regenerative braking also worked remarkably well - you save the wear and noise of 'conventional' braking, and it slows you really noticeably. Great for descents or stops planned ahead, but you definitely need good brakes too for more urgent stopping.

So, all in all the BionX seems to live up to expectations, with completely silent power assist which is strong, smooth and responsive, with the added bonus of regenerative braking which really works. But the price for the kit alone is more than many midrange complete bikes - which means it's a substantial investment indeed.

Peter Eland

Available via Zyro dealers: see www.zyro.co.uk


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