Tern is internationally recognized and renowned for their high-quality folding bicycles, and electric folding bikes! The Vektron was their first major entry into this category in 2017, using the Bosch Active line system, but they did have a couple of conversion models dating back to 2014 that used the hub motor BionX system. With the GSD, you get a more powerful Bosch Performance Line mid-drive that keeps weight low and center on the frame, an option for two battery packs that can deliver 150 miles of range per charge, and a frame that is stiff, sturdy, and capable of hauling up to 400 pounds of people or goods. Even though this is technically not a folding electric bike… it does fold a bit. The handlebar post swivels, the stem can be angled completely up or down, and the telescoping seat post uses quick release levers to drop easily. Perhaps the most innovative feature isn’t the folding parts, but the four pegs built into the rear section of the bike and rack that allow it to tip back into a vertical position. And, to be pretty stable in that upright position! This allows the bike to easily fit into elevators, closets, and other tight spaces that can fit an average sized person (the bike takes up similar dimensions). Even though the bike weighs a bit more than an average electric bike at 67.7 lbs, tipping it up isn’t too difficult thanks to premium hydraulic disc brakes. These brakes, along with the tapered head tube, wider Boost hub spacing, and sturdy thru-axles are all reminiscent of a nice mountain bike. The 180 mm brake rotors are very large for such small wheels, and that provides a huge mechanical advantage when stopping. The brake levers are adjustable so they can fit smaller hands and even with one hand filming and the other using the brake I was able to stop with no issues. Yes, with a top assisted speed of 20 mph, fantastic range potential, and plenty of stopping power, my biggest focus when testing the bike was on stability and comfort. And frankly, it’s a bit of a compromise on these fronts.
The motor driving this bike is a Bosch Performance Line Cruise. It fits near the middle of the Bosch line in terms of power, and is a step up from the Active Line used on the Vektron folding model mentioned earlier. This motor offers up to 63 Newton meters of torque and listens for rear wheel speed, pedal cadence, and pedal torque signals over 1,000 times per second! That translates to excellent climbing ability, as long as you switch gears appropriately, and start/stop power delivery that is near instantaneous. When you’re pedaling through a city environment, with a heavier load, that kind of quick response is critical and it pairs nicely with the strong braking configuration touched on before. The motor is a geared design, and it produces some high pitched whirring noises when operated at full power and pedaling at high RPM… but I love that the motor actually supports faster spinning, up to 120 RPM, while some competing models, and even the Bosch Active Line, only go to 100 RPM. As someone with a sensitive knee, I prefer to spin faster with less force and this higher RPM support also means I don’t have to switch gears as frequently to go faster. When you’ve got a 10-speed cassette to explore as you do with the GSD, it’s nice to be able to achieve a range of speeds with each gear vs. having to use the triggers so frequently. The trigger shifters work well, and are only mounted on the right portion of the handle bar because this ebike uses a one-by drivetrain (only one chainring). The chain is completely covered at the bottom bracket area to keep your pants or dress grease free, and even though there was some bouncing of the chain, I imagine that it would not drop off easily. One unique hardware feature of the Shimano Deore derailleur that Tern specced here is a one-way clutch lever that tightens the chain when pushed to the up position. It’s a feature I most frequently see on mountain bikes that encounter a lot of rough terrain, but it’s helpful here because the chain is so long. Overall, this is one of my favorite motors and I feel that the drivetrain is great. Shops and end-users tell me that Bosch is reliable and I know that they have been producing and selling variations of this motor globally since 2013.
Powering this electric bicycle is the proven Bosch Powerpack 400… which is not quite as exciting as the newer Powerpack 500 (which offers ~25% more capacity and looks the same). The good news is, the mounting interface on the bike allows for backwards compatibility and can work with the 500 watt hour pack if you want it. Actually, there are two of these mounting interfaces because the Tern GSD is one of the new double-battery ready e-bikes. You can get an additional Powerpack 400 right out of the gate for ~$800 and effectively double your range. I love that both packs are positioned low and center on the frame while staying out of the way of passengers and cargo and being protected by the metal frame tubing. Unlocking and pulling them off can be a little bit trickier than single-battery bikes I have tested, but it wasn’t too bad. And, one of the coolest design features is that both packs can be charged simultaneously on the frame by plugging the charger into the single accessible slot (for the pack nearest the seat tube). It’s convenient and satisfying to fill this bike up, and it happens faster than many other e-bikes thanks to the Bosch 4 Amp charger. This charger only weighs 1.7 lbs and is compact enough to fit into the bottle pouch at the end of either side-bag that come with the bike. Other things I appreciate about these batteries is that they have a molded loop-handle built into the top for safer transport, an LED power level chart built into the side, and can be charged off of the bike with the same interface (no dongles or adapters required). Weighing in at ~5.4 lbs, I usually take batteries off before transporting my electric bikes by car rack or if I have to lift them, and the front wheel might also reduce weight, and is easy to remove with the quick release system along with the seat post and saddle.
Operating the Tern GSD is a snap. Once the battery (or batteries) are mounted and charged up, just press the power button on the top edge of the little Purion display panel near the left grip. The thing turns on quickly and is clear and easy to read. It’s smaller than the popular Bosch Intuvia, doesn’t have a functional Micro-USB port, isn’t removable, won’t swivel to reduce glare, and doesn’t offer readouts like average speed, max speed, clock, or shift recommendation… but it’s less prone to damage and super simple to use. There’s a + and – key built into the left side of the casing and their primary function is to increase or decrease assist power. You can go from Off to Eco, Tour, Sport, or Turbo. The higher you go, the more power is delivered and the faster you may go. The secondary function of these buttons is to activate the lights (by holding plus), or cycle through trip stats (by holding minus). Those trip stats include trip distance, total distance, and range. Range is my favorite because it offers more precision than the 5-bar battery infographic at the top of the LCD screen. It is calculated based on your remaining battery charge level, chosen level of assist, and the last mile of riding efficiency. The final button on the display is walk mode, which is positioned at the lower edge and requires a push, and then hold of the plus button to use. I was able to enjoy this feature while exploring a crowded park in Brooklyn, New York, and it really made our little adventure fun and relaxing vs. uncomfortable and strenuous. I can only imagine pushing a fully loaded cargo bike vs. the still-heavy unloaded demo model we used for this review. I love walk mode but not every company offers it or even enables it when they do have the same drive system as Tern has used here. It’s a feature that Bosch allows their partners to have some choice on… so thank you Tern!
I’d like to finish out this review by apologizing for the extra-close camera work in the video review above. My camera got a bit messed up and recorded on narrow setting vs. medium and that might have been uncomfortable for some viewers. I was so excited to cover this product because it offers something unique and useful in the space. So many companies have different sized frames, different colors, slightly different components etc. but Tern invented the GSD from the ground up. It really can help you “Get Stuff Done” and empower a family to live healthier and have more fun. For me, it was a little bit jarring, but the larger tires did make a difference for stability and comfort and the saddle felt nice. I was amazed how stiff it felt to ride with a heavy load on the back and inspired again and again by all of the attention to detail. From the vertical stand design to the folding stem and rubber strap secure feature, the fork spring with quick-release, to flip-out pegs. It’s quite capable, even though it’s compact and the value of the components they used matches or even exceeds the price being charged. I suppose they saved money by only having one frame size but the multiple color choices are great. Big thanks to Tern for partnering with me on this review and sending a demo unit out to Propel bikes in Brooklyn for me to film in a city environment. It was neat to see this new model back to back with the Tern Vektron and compare the price and weight. They each have their niche but I enjoy both and am excited to see how Tern refines them over the coming years or expands their offering with even more custom built electric bikes.
- Tern is a well-recongized and trusted company with years of folding bicycle and now folding electric bicycle expertise and leadership, their folding handlebar post with rubber clasp, Andros adjustable stem, and telescoping seat post feel solid and can accommodate riders from 4’8″ to 6’4″ according to their website
- Most electric bikes are rated to carry 250 lbs or maybe 300 lbs but the GSD can handle up to 400 lbs! That’s two adults and a child, lots of groceries, lumber for a project etc. and the thick thru-axles and premium tires (with puncture protection) earned my trust
- Safety is a hug deal to me because I sometimes ride in the early morning or evening surrounded by traffic, so I love the bright color options, reflective tires, reflective stickers on the frame and pannier bags, and the integrated lights that run off of the main battery
- Some electric cargo bikes feel flexy because they are so long and lack the proper reinforcement, some position the battery or motor at the end vs. the center but the Tern GSD felt very solid and stiff, even with an adult riding on the back
- The motor used here is one that I have reviewed hundreds of times before on other electric bikes and it has earned my trust as being reliable, it’s also very responsive and powerful, I have never felt out of control with it or like it wasn’t helping me enough on a hill (as long as I had shifted gears properly to climb)
- The motor, battery, and nicer Shimano Deore 10-speed drivetrain allow you to get excellent range by shifting gears to climb or hit and maintain the 20 mph top speed, it’s a lot more efficient than a hub motor system because it’s empowered by your shifting vs. only having one gear ratio to work with
- I love how the battery pack or packs can be charged on and off the bike, this is convenient for those who commute to work and need to fill-up for a long ride home or errands and then home, the Bosch charger offers 4 Amps vs. the standard 2 Amp which is slower, Bosch also offers a compact 2 Amp charger for people who want an extra but need to reduce weight and size
- Power and range are important but so is stopping, especially with a heavier bike and potentially more gear or multiple passengers, the Magura MT5 brakes are fantastic! You get adjustable-reach levers and quad-piston calipers vs. the standard dual-piston design which spreads out force and improves cooling, the 180 mm rotors are almost overkill for the 20″ diameter wheelset, these are basically mountain bike brakes meant for full sized wheels
- For such a custom ebike with premium drive system, drivetrain, brakes, fenders, lights, and bags… I feel like the ~$4k price point is pretty good! Yes, it’s still a lot of money, but this thing is like a truck and could really change how you interact with your community, it can also be shared between multiple riders
- Tern chose the kickstand well, it deploys and stows easily while offering much more stability than a single-side stand that you’d find on most traditional bicycles, I also like the spring that keeps the front wheel relatively straight for loading and steering with heavy loads
- So many awesome accessories! Whether you’re taking people or cargo, there are plenty of ways to stow gear, I especially like that there are pannier supports so you could use this for long distance touring, the front rack mounts to the head tube and stays straight as you turn (so it doesn’t impact steering) and the included pegs make it easy to bring a friend somewhere without having to spend extra money
- The swept-back handlebar, ergonomic grips, and plush saddle made the bike a lot more comfortable than it could have been, they pair nicely with the fat tires if you lower the PSI a bit (just don’t go too low or it could cause a pinch flat, they recommend 30 to 65 PSI and I was riding at 30 PSI as a 135 lb rider)
- Wider tires increase the size of your contact patch for grip, provide stability, and offer float on soft terrain like grass, they might not roll quite as efficiently as a more traditional 2.15″ diameter but they are perfect for dealing with heavier loads
- With a lower 20″ stand over height, you can easily step-thru the frame vs. having to swing your leg up and over the saddle or over the rear rack (which might be loaded with cargo), I like that the top tube and portions of the side stays have clear plastic stickers to keep the paint looking nice
- The fenders are extra wide, sturdy, and have flexible mud flaps and the chain guard offers full-coverage of the front sprocket and chain going back pretty far… so your pants or dress should stay clean
- My understanding is that you can charge both batteries from the single charging port on the bike, this is convenient because you don’t have to remember to unplug one battery and plug the second in (this is only relevant if you buy a second battery and leave both packs connected to the frame)
- I was a little bit surprised that the Tern GSD doesn’t come stock with a Powerpack 500, you get the older slightly-lower capacity Powerpack 400 by default and can upgrade or get a second 400 for ~$800
- Even with the fat 2.4″ tires (vs. the Tern Vektron’s 2.15″ tires) the GSD can still feel jarring and unstable compared to a full sized bike, I lowered the PSI to 30 (the lowest on the 30 to 65 pressure range stamped on the tire) and that helped a bit but I still might get a seat post suspension for the upper 30.9 mm portion and use a shim like this
- The smaller diameter wheelset makes the bike easier to mount, load, and stabilize when starting or stopping but it also brings the derailleur and kickstand lower, the clearance on this bike is less than many other cargo models so be careful when parking near a curb or other low obstacles
- Very minor complaint here, but the Bosch Performance Line motors have a reduction gear that creates some friction when pedaling vs. a 1 to 1 pedal ratio, the smaller sprocket also brings the chain very close to the frame tubing which could create some noise or nicks on bumpy terrain
- For how compact and little this e-bike looks, it’s actually pretty heavy at ~67.7 lbs because of the additional reinforcement tubing, long rear rack, thicker rims, and fatter tires
- The compact Bosch Purion display panel is not my favorite because you cannot remove it and the integrated Micro-USB port is not active for charging accessories (just performing software upgrades and diagnostics), seems like a missed opportunity when you potentially have two battery packs to draw from and are using your phone for GPS or music etc. but I do see how the larger Bosch Intuvia might not have fit with the adjustable Andros stem setup