Tern / BionX Link D8—A Prototype Becomes a Reality

Tern / BionX Link D8—A Prototype Becomes a Reality.

The Tern / BionX Link D8 rides as good as it looks.

If you haven’t considered how convenient and fun a folding electric bike can be, I would suggest starting now. Between the ease of transport, its storage needs and just plain ride ability, they are great. Much of what I report on and ride is either folding or electric, so I just love them both combined. These two companies are well known in bike circles, seeing them come together has been exciting for me. I had the prototype for almost two months, and am now riding the awaited production model.

I’ve noticed a few changes, none drastic. My first BionX test model host bike was the Tern Link P9, a now discontinued model. From the beginning, Tern claimed the two bikes they would produce with the BionX system were the Link D8 and the Node D8. That is what they’ve done. The Node is a 24” wheeled folding bike, and this Link D8 has 20” wheels. It comes equipped with fenders and a rack, kickstand too. With a solid ride and a quick fold, the D8 is a great bike, regardless of if you get it with the BionX or not.


Ready for fun rides just about anywhere, the beach seemed like the place to go.

Tern pays a great deal of attention to the little (and big) details that make for a nice folding bike. It doesn’t take much time to realize this during your ride, or just spending time with one of their products. An easy way to see this is to compare the frame latches with any other folding bike on the market. Their use, their feel, and the way they keep the frame to zero flex speaks volumes. From top to bottom, front to rear, every Tern bike I have ridden just shows much about what they want you to feel during a short ride, or a long one.

In the world of E-bikes this is a real lightweight, pulling just under 45 lbs. on my cheapo fish scale. I believe about 18 of that is the BionX motor and battery, the rest being the host bicycle. The battery is removable to make the lift weight less, yet I just leave it on when popping it in the trunk or back seat. The battery doesn’t affect the fold and keeping them together makes sense for me. Some might like the removable factor if you need to recharge the battery away from your bike parking area.

I found the electrical programming of this to be a touch better than the prototype. It has smoother response whether using the automatic pedelec or the push button throttle. If you are not familiar with the BionX E-bike conversion system, here are a few highlights. It is a silent direct drive motor. The main electronics are located in the motor housing. It offers dual control, with the pedelec function using torque sensing control. This means, rather than reading pedal movement, it reads (and responds to) torque pressure on the pedals. This is something I call intelligent control. It makes for a very satisfying way to experience an electric bike.

The silent, direct drive BionX motor is a great match for the Tern Link D8.

Although fully silent, a direct drive motor does give up a little in pure hill climbing power at the lower speeds. Yet in the over 10 mph range it proves to be quite the powerhouse in that respect. Some might think the smaller wheels (than a full-sized bike) might change the characteristics of the power and speed, yet it feels like other BionX powered bikes I’ve ridden. A direct drive motor has fewer moving parts (more reliable), but does have slightly more rolling resistance (basically not noticeable) than it’s geared motor brother.

Before I tell you the couple things I don’t like, let’s talk riding fun and performance. Just like the non-powered version of this bike, the Tern Link D8, it is a comfortable, easy ride. The steering is quick, but not as to cause uneasiness or instability. Eight speeds is plenty for most every riding situation. The standard version could stand a bit lower climbing gear, but with the power of the motor helping, this is not issue on the Tern / BionX. Top gear matches the bike and motor well.


With lots of info and easy use, BionX has your needs covered with the handlebar mounted display.

Learning and using the controls are second nature for most experienced E-bike riders. There are 4 buttons on the display that do all your bidding. There is another pair at the handgrip that do the same function as two of the display’s buttons. Those are the plus and minus buttons for the assist and regen functions. The other two on the display control power on/off, display back lighting and the mode of the display readout.

There are four sensitivity levels of power assist and four of battery regeneration. They are set by the plus and minus buttons. During motor assist, each level chosen can make the motor help at higher and lesser amounts of pressure on the pedals while riding. The throttle button will work at anytime, yet not while the bike is stopped. This safety feature is so needed, but overlooked by other companies with torque-assist control systems. I applaud BionX with the smart thinking that goes into their motor-assist programming.

The regen not only returns some of the energy to the battery when slowing or descending, but acts as a drag brake as well. On downhill runs this saves brake wear and heating. This brings me to dislike #1. On the rear brake handle is a magnetic reed switch that sets the controller to full regen before the pads actually touch the rims to actuate the brakes. Full is just too much slowing, especially during regular riding. The varied levels of regen (drag brake) are settable by much toggling of the buttons, yet need to be re-toggled to get back to your power-assist modes. This is a BionX feature I’ve never liked. BTW, some feel regen is more of a marketing novelty than necessity. I am still on the fence, but continue to lean towards novelty and un-needed complexity.


The 48 volt lithium battery mounts to the frame for a good balance. It is removable with a key for remote charging or to make the bike easier to lift.

Theoretically you can reset the level of full regen in the bike’s computer, but don’t even try. I know all too well from previous experiences you don’t want to go into the BionX menus to alter the settings of any of the parameters. BionX is hush-hush on the settings and the on-line info is shaky to say the least. They (BionX) tell you how to change the wheel circumference settings for the speed readout and how to set the clock. The first you won’t need to alter on this bike and the second might need to be set on delivery and twice a year for daylight savings changes.

Did you think I’d let this year end without my standard pose with today’s test bike?

A minor BionX gripe is that the unit gets turned on all to easily when moving, touching and folding the bike. That button is on the upper, inner edge of the display and bumped often. It tells you with a series of beeps you have turned it on. For me this happens way too much. Don’t worry though, it will turn itself back off in about ten minutes if you aren’t riding. Those two things aside, I think that BionX has an exceptional product, and that it is a great match for this quality folding bike.

I’ve taken it on so many cool rides, with a few more planned before its eventual return. I have yet to see it on Tern’s website, but I am assured it is fully available from all their dealers. With such a good reputation from both makers, I can’t see any reason to not consider it for your next bike.

Ride with power, Turbo Bob.

“It is the unknown around the corner that turns my wheels.”—Heinz Stucke, German long-distance touring cyclist.

Tern on the web and Facebook



BionX on the web and Facebook



A walk around video I took of the Tern / BionX Link D8


About Turbo Bob's Bicycle Blog

E-bike Enthusiast Vintage Bike Enthusiast
This entry was posted in E-bike test reviews, Folding Bike test reviews. Bookmark the permalink.

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