The New Tern Vektron S10 Brings Agility to Folding E-Bikes
Price: $3,699
Weight: 48.6 lb. (claimed)
Use: Commuting, grocery-getting, cargo hauling
Battery life: Up to 80 miles (on Eco mode)
The right bike for: Conquering daily commutes and errands and bringing your kid along for the ride.
The 2019 Tern Vektron S10 improves upon the original’s über-compact folding design with more power and a bigger rack. The Bosch Active Plus motor delivers 25 percent more torque to help you conquer hills on the nearly 50-pound bike, and the 10-speed Shimano Deore drivetrain gives you options when you’re pushing more of the weight in Eco mode.
Tern uses 20-inch wheels to position the weight lower to the ground and keep the bike from becoming top-heavy while hauling cargo on the integrated rear rack, which is now longer and lower, thanks to a diagonally mounted battery. It’s a bike that disguises its heft well and folds up to stand on its rear end for a portable package that goes wherever you do.
Fast folding and a low-slung design
Tern’s OCL+ frame hinge returns on the 2019 Vektron S10; it uses a tall hinge to minimize flex at the joint and an auto-lock system to ensure the hinge doesn’t open while riding. There’s another hinge at the top of the steerer tube to fold the long stem and handlebars down, and the folded-up bike stands vertically on the rear rack to minimize floor space usage. The battery is now diagonally mounted to allow for a longer rack that sits lower on the frame. The new rack has eight mounting points for cargo and child seats, and an adjustable stem allows riders to modify handlebar height and reach.
More torque and a 10-speed drivetrain
The Bosch Active Plus motor is the focal point of the S10’s drivetrain; it churns out 50 newton meters of torque in Turbo mode, compared to previous S10’s Bosch Active motor that generated 40 Nm. Pedal assist tops out at 20 mph, and according to Tern founder Josh Hon, the Active Plus generates less friction while coasting. A 10-speed Shimano Deore Shadow+ shifts the 11-36t cassette, and the single chainring up front has 52 teeth. Magura MT4 hydraulic discs bring the beefy Schwalbe Big Apple tires to a halt. There’s also a Valo Direct light with 150 lumens of road-illuminating power built into the stem. A full list of compatible bags and baskets is available on Tern’s website.
Agility meets powerful pedaling
The Vektron S10 is designed for riders between 4-foot-10 and 6-foot-5, and setup is fast thanks to the two-tier seat post with quick release clamps and an adjustable stem. Unfolding the bike takes two clicks from the clamps at the top tube and head tube. Once riding, you’ll notice Tern’s concerted effort to keep the weight low: With its steep head tube angle and 20-inch tires, the S10 handles like a moped. It’s maneuverable at low speeds and easy to turn around within a single lane of traffic; at higher speeds (past the limits of the pedal assist) the S10 can feel unsteady at initial turn-in, so leaning the bike with your hips and slowing down handlebar input yields the steadiest cornering. While riding, though, there’s no noticeable flex from the frame’s folding points, so kudos to the burly clamps.
The motor's Eco mode works well for flat-ground efforts, but the setting reveals the bike’s heft, contributing a slight boost equal to just 40 percent of your pedaling effort. In Tour mode, with a boost matching your own effort, the S10's power balances the weight so riding it feels like a mid-range hybrid bike. The Sport mode kicks in 180 percent of your effort, enough to conquer steep hills with a modest sweat from the rider. Turbo mode boosts up to 270 percent of the power you put to the cranks and feels fast on any terrain, although there’s a slight braking sensation when the motor reaches its 20mph limit and motor-assist cuts out.
Tern claims an 80-mile range, but expect less than that if you're using Sport and Turbo modes often. We used approximately 25 percent of the battery life on a 12-mile ride with 1,600 feet of elevation gain, alternating between the top three modes. Flatter routes will increase battery life.
The wide Big Apple tires provide a slight suspension effect (we ran them at 35 psi), and their grip is evident when you lean on the Magura discs, which are plenty powerful and smooth as you increase your pull on the brake levers. The gel-cushioned Porter+ saddle is plush without being too squishy, and the Ergon GP10 grips are comfortable, albeit narrow for wider hands. We didn’t get a chance to haul any cargo on the improved rear rack, but as a bicycle for commuting and daily use, the new Tern Vektron S10 is user-friendly and packs plenty of zip.
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