The Tern Link D8 with BionX is an ultra portable folding electric bike with a higher-end drive system from BionX. It folds perfectly with the battery attached but you can also take it off to reduce weight or charge separately. The motor offers excellent torque, multiple levels of assist and regen, regenerative braking and throttle operation and it runs extremely quiet. Both Tern and BionX are respected manufacturers, known for quality builds and good support. In my opinion they’ve created one of the most functional, well balanced and beautiful folding electric bikes around with the Link D8. Its smaller 20″ wheels enable the super small form factor (when folded) but aren’t as smooth as the larger 24″ wheels chosen for the Node D8. Depending on your needs, either bike performs well but costs a bit more than some entry level folding ebikes that lack assist and some of the nicer accessories in use here.
The motor driving the Tern Link D8 electric is a 350 watt gearless direct drive hub from BionX. It’s located in the rear wheel and painted black to match the Tern frame. Note that this motor has a larger diameter and higher weight than some equally specced gearless hubs but delivers increased toughness and quieter operation. I’m not aware of many folding electric bikes that offer regenerative braking or regen modes but the Link D8 with BionX has both. There are actually four levels of regen here to help you recapture energy while simultaneously slowing the bike and sparing your brakes when coasting down hills. This feature can also be used as a form of increased challenge if you want to raise your heart rate and don’t have any hills around to climb. While this bike does not have a rear quick release mechanism (only on the front wheel) the rear wheel remains easy to service because the motor has a built in torque sensor vs. an external dropout strain gauge.
Powering the Tern Link D8 is a BionX-made Lithium-ion battery pack containing Panasonic cells (known for being super high quality). It offers 48 volts of power which is above average. This has several benefits including increased torque, improved climbing ability and more efficient electricity transfer. In terms of overall capacity, this pack is slightly smaller than the stock BionX kits but that enables the folding feature mentioned earlier and keeps the overall weight of the bike down. At 42 pounds (with the 6 pound battery attached) this isn’t the world’s lightest folding ebike but that’s due in part to the high quality fenders and rack that add utility. You could always remove these extras to shave a bit off and reduce any rattling noise that can develop over time with use, folding and storage.
The control panel on this bike is one of my favorites because it’s slim, removable, backlit and packed with readouts but not overly complex to use. It’s a second generation display from BionX with four buttons (two on each side) that are symmetrical – designed to be usable on the left or right hand side. What I’ve found is that I usually only press the upper right hand button on the display to get the bike powered up and then rely on the stand-alone button pad and throttle which are mounted on the right handle bar. Many ebikes forego throttles but it can be useful when your legs get tired (especially on a smaller bike like this) or when trying to balance groceries or packages. The rear rack helps out with the latter experience but you get the point… imagine crossing a puddle and wanting to keep your feet raised temporarily but still needing to move forward, that’s where throttles can really shine. On this system (as well as other BionX) you have to get the bike up to 2 mph before the throttle will activate and this is a safety feature. Aside from the display and buttons I like the ergonomic grips and simple grip-shifter on the right side of the handlebar. You might consider adding a bell and lights to this setup depending on your intended use. I should mention that only the right brake lever has a motor cutoff and regen activator built in. If you brake with the left lever, regenerative braking will not activate. This is a minor gripe and again, a design feature related to all BionX kits at the time of this review.
The Tern Link D8 with BionX combines two proven platforms. The locking mechanisms and folding design from Tern are superb and I love the magnetic clasp designed to keep the bike from unfolding. The silent and durable motor from BionX feels zippy and the removable battery is very convenient. I’m a fan of pedal assist but see the value in throttles so it’s nice that this folding ebike offers both. The eight speed cassette delivers a good range for climbing or pedaling fast (which can be precarious on a smaller 20″ wheel bike like this). I like the reflective sidewalls on the wheels and am okay with the standard v-brakes and plastic folding pedals. The crank arms on this bike are actually quite long for a smaller bike and that makes pedaling feel natural. While many folding electric bikes opt for rear mounted batteries I love that this one has a more balanced weight distribution and appreciate that they even added water bottle cage bosses on the side of the downtube so you can still bring some fluids along (you could also store water in a bag on the rear rack). If you’re looking for quality but need an extremely small footprint on your boat, RV or closet then the Link D8 would be an excellent choice.
- Solid two year warranty on the frame, drive system and battery pack – Tern and BionX are both large, well established companies
- Beautiful aesthetic with matching black and blue frame, custom black hub motor and black battery casing featuring co-branded Tern + BionX art
- Just about every drive mode you could ask for including four levels of torque sensing pedal assist, four levels of energy regeneration and variable speed trigger throttle
- Independent button pad on right side of handle bar is easy to reach (to change assist mode or use the throttle) doesn’t require that you take your hand off the grip to use
- Battery pack can be charged on or off the bike, does not have to be removed for the frame to fold completely
- Motor is powerful, durable (thanks to the gearless direct drive configuration) and very quiet to operate
- Full length front and rear fenders with mud flaps, rear carry rack includes built in bungee cords for securing cargo
- Several nice extras including reflective sidewalls on tires and backlit LCD display panel for improved safety during evening and night riding, ergonomic grips for improved comfort and magnetic clasp for secure folded position
- Good weight distribution with the 9 pound hub motor at the rear and the 6 pound battery pack mounted forward on the downtube
- BionX battery has a deep sleep protection feature that keeps it from discharging in a way that could hurt the battery over longer periods of storage
- Satisfying to pedal thanks to the longer crank arms and eight speeds cassette, good for climbing or riding faster
- Smaller 20″ wheels allow the bike to achieve an extremely small folded footprint but don’t offer the same cushion or gap-spanning potential as larger wheels, consider the Tern Node D8 which has 24″ wheels if this is a concern
- Only the right brake lever cuts power to the motor and activates power regeneration mode, it would be nice if both did
- Rear wheel does not feature quick release, will have to use traditional tools during maintenance or fixing a flat