Tern are touting the Vektron as "the world's most compact Bosch e-bike". This Active-Line-powered 20-inch folding bike certainly does pack down small. And, importantly, it rides really well. The Vektron range is also being expanded, with cheaper Bafang mid drive bikes added to the line-up, and that's a good thing too.

Tern have been making folding bikes since 2011 and they've built a reputation for making high-quality bikes with a compact fold. The company is now moving out in other directions: there's a range of full-size commuting and city bikes coming, and of course there's the excellent Tern GSD compact cargo bike. The Vektron is the company's first Bosch-powered folder. It's not their first e-bike – the eLink joined the range in 2014 and used a Bafang mid motor. But while the eLink was an adaptation of an existing bike, the Vektron has been designed from the ground up as an e-folder.

"The Tern Vektron is the happy marriage of everything we love about a Bosch e-bike, and our expertise in folding technology," Josh Hon, founder of Tern, said of the bike. "By making a quality e-bike truly portable, we've created a product that will convince even more people to ride more regularly." The Vektron has the smallest folded size of any bike in the Tern range, and will accommodate riders from 140cm to 195cm.

The bike has an alloy frame with a central fold, and a Bosch Active Line motor, with the 400Wh battery placed behind the seat tube.

The seatpost is telescopic, with two quick releases allowing a long extension whilst making sure that the fold size remains compact.

As well as the main frame hinge there's a 45° hinge in the steerer to fold the handlebars down. Once everything is folded it's a very compact package, which looks like this:

What with carrying 7kg of motor, battery and assorted gubbins the total weight of the bike is a claimed 21kg, so it's not a lightweight. It's designed so that you can roll it around on its two wheels though, using the seatpost as a sort of handle (you can extend it to suit). You have to push it rather than pull it, as the pedals get caught if you drag it backwards.

Tern have also brought out a rack with caster wheels on it, the Rapid Transit, which allows you to push the bike around as you would a suitcase.

There's a magnetic catch to keep everything together, and this rubber strap too which guarantees the bike won't unfold as you're pushing it around.

The ride: solid and enjoyable

We originally rode the Vektron at the Eurobike show in 2016, but since then we've had a bike on loan for everyday use around Bath. The 20-inch wheel is a popular one for city e-bikes as you get a nice compact bike with the ride position, and much of the ride feel, of a full-size bike. I've ridden the Kalkhoff Sahel Compact, the GoCycle, the Orbea Katu-E and the Peugeot Ae21, and I have to say that the Tern isn't really giving anything away to any of them in terms of handling. The quick release hinges snap everything tight and there's very little flex in the bike at all; a little in the long steerer, but nothing that's at all an issue.

I'm 1.89m and I didn't have any issues getting comfortable on the Tern. There's plenty of seatpost, and the adjustable stem allows you to raise or lower the bars over quite a distance, as well as easily tilt them to your preferred angle. All the controls fall easily to hand and the Shimano Deore hydraullic brakes are real one-finger stoppers, with masses of controllable braking power. The Ergon grips are comfy too. The bike is adjustable enough that everyone in the family could comfortable ride the Vektron, down do Joel who's only 9 (albeit a tall 9, at 1.55m). If you're looking for a bike to fit everyone, this could well work for you.

The Bosch Active Line motor was faultless, as usual, with the four assistance modes giving an option for pretty much anything in conjunction with the 10-speed derailleur transmission. The 400Wh battery will have enough range for anything you're likely to want to do on the Vektron. This isn't a bike you're likely to be doing huge miles on, it's designed for mixed mode and short-hop riding. The battery life is okay; It's not the best for a bike with this motor and battery combination that I've tried, but range was never an issue. On the flat you'd easily get 50-60km out of the Vektron in the lower modes; if you're in turbo all the time and just going up and down hills you can run through the battery in half that.

The bike also gets integrated lighting, with a 150-lumen Valo 2 light at the front and a rack-mounted rear. The lights are plenty bright enough for about town, and even venturing out into the unlit lanes there was plenty enough light to ride by. The front light has a German-style cut-off beam, so all the available light is directed at the road.

Folding and carrying

Handling the bike when folded was okay, although the 21kg overall weight is an issue. If you're pushing your folded bike onto the train it's pretty manageable, but lugging it up and down stairs is more of an issue, as is putting it in the boot of your car.

I tried a couple of mixed mode commutes on the train over to Bristol for meetings, and from where I live high on the outskirts of Bath it's more ore less perfect, provided you're prepared to spend time waiting for the lift at either station: The Vektron isn't easy to carry up and down stairs. I could do it, but I'm a fully fit 94kg bloke and even I didn't find it much fun. If you're slighter of build you'll struggle. But if there are lifts and the only thing in the way is the topography (and there's plenty in Bath and Bristol) then the Tern is excellent. There's more than enough juice to do the hills at both ends and still have plenty left over. I rode the Vektron all the way to Bristol and back too (40km) just to see what it was like, comfort-wise, on a longer journey. It was fine: it wouldn't be your first choice for a big ride but it didn't give me any problems.

I also tried lobbing the Vektron in the car and using it for a mixed journey when I went to Cardiff, allowing me to park a few miles outside the city centre and roll in along the Taff Trail. It's an excellent way to get into a city if you know there's a simple and quiet route you can do by bike. The Vektron packs up pretty small and would fit in the boot of most cars, although again you'll need some upper body strength to get it there.

Issues during testing

Nothing much to speak of went wrong. The only real issue I had was with the rear derailleur hanger. It's either a bit fragile, or in a more vulnerable position than usual, or both. Either way I had to bend it back into shape a couple of times when the gears started skipping and I realised that was the problem. There doesn't seem to be anything out of the ordinary about the mech hanger, so it might be I was just unlucky, but it's worth noting here.

Overall: a high quality bike that's fun to ride

I very much enjoyed my time with the Vektron. It's easy to ride and fold, and it would make a lot of sense for anyone with a mixed commute or limited space. At £2,999 it's not cheap, even considering the level of equipment used, so it's a considered choice, but if you want something that'll last then it's definitely one to recommend.