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12.7kg £2200 (fully equipped)

Tern are a long standing designer and manufacturer of high quality folding bikes and evolved out of major folding bike maker Dahon which has mass-produced many thousands of folders since the oil crises of the 1970s gave a big impetus to cycling in general and folding bikes in particular.


Since the emergence and huge popularity of Brompton bikes from the 80s onwards the market for compact and securely folding bikes has also taken off. Traditional folders had 20” diameter wheels and a fold in half-frame and when the Brompton came along its more manageable (and in most cases lighter) folded package proved to be a revolution in the world of folding bikes. Criticisms of the Brompton were centred around what some found a rather ‘twitchy’ ride due to the 16” wheels and complaints about weak braking and over-complicated gear changing.

folding bicycle cycle track countryside

Tern are looking to combine the magic ingredients of folding bike success in the BYB (short for Bring Your Bike). They are aiming to produce a bike with a faster, slicker and more stable ride than a 16” wheeled competitor, but incorporating compact and secure folding elements not usually seen on 20” wheeled folders, at the same time.   


The S11 is the top of the range BYB model, a full 1.6 kg lighter than the lower spec P8 model and featuring high end bike technology such as Kinetix Pro X wheels with paired spoke technology and an 11-speed Shimano Ultegra Shadow RD derailleur.

folding folder bike bicycle urban tern BYB

The Fold


I start with the fold as this is at the heart of what Tern want to achieve with the bike – Tern say the BYB folded bike is 30% smaller than traditional 20" folding bikes, and folds small and slim enough to fit conveniently into lockers, closets, or any narrow space.


The double-hinge frame mechanism and the rear patented anchor bolt mechanism, combined with the Metro Transit 

folded folding bike bicycle

Rack with integrated castor wheels, may look like it’s a complicated bike to fold at first, but it isn’t. 


Drop the seat-post, undo both frame-hinges and concertina the bike back on itself to lock everything place using the anchor bolt. You can leave the handlebar post extended if you wish to stand the bike upright on the rear of the rack and use the bars as a ‘trolley handle’. Alternatively you can unlock the bar’s Andros stem mechanism and align it vertically before folding the bars down. There is also a removable pedal on the side that sticks out of the folded package and this can the locked away on the frame. 


It’s that simple – a matter of seconds and no tools needed.

frame fold hinge welding

There is a bespoke Pop Cover available, too, as some transport operators require folded bikes to be covered to count as regular luggage. The cover’s design means it fits in seconds and also means it allows you to use the handlebar post for the trolley function too if required.

Wheeling BYB 3 small.jpg

All in all I was very impressed with the key folding aspects of the BYB. At 81cm x 51cm x 33cm it doesn’t rival the smallness or quickness of some other folds but once folded it stays together very securely and is very easily portable, being reasonably light to carry and lift and it also has the easy-wheeling feature as described. Indeed 12.7 kg is a respectable weight for a fully equipped folder with 20” wheels – including items you don’t often get with folders such as a rear rack, full length mudguards and kickstand.

folding bike rack mudguard fender rear red light wheel tyre

Tern claim that the BYB is 30% smaller than other 20” wheeled folders. A folded volume of around 136 litres is actually 45% smaller than the similarly well-equipped Verge S8i which measures 248litres volume when folded.


The fact it can sit lengthways or vertically gives it flexibility to fit into a variety of spaces and the clever design means you can also place it on the floor without it toppling over.   


Frame hinge-joints have been something of a weak spot on cheaper, older models. This certainly doesn’t appear to be the case on the BYB. Its patented TFL hinges have sliding bearings that are serviceable and the hinge levers are easily tensionable on the go but also spring lock back into place once adjusted so that they should stay at that tension for fold after fold. The frame at the hinges joints themselves looks massively well constructed and the hinge-joints feel to lock really solidly.

fold hinge lever bike bicycle frame

The Physis RF handlepost hinge is similarly reassuringly strong and stiff.     


The Ride


Before you even start to ride you notice just how easy the BYB is to alter to fit your body size and desired riding position. The telescopic seat-post design gives loads of height adjustment whilst the Andros stem gives plenty of fore and aft bar adjustment, whether you like a sporty, leant-forward position or a comfy upright ride. Tern say it suits riders from 147 to 195 cm (4’10” – 6’5”). 

folding folder bicycle cycle bike

Once underway pedal pressure results in snappy acceleration thanks to the stiff frame and the gear changes are crisp and quick thanks to the 11 Shimano Ultrega Shadow RD gears. The RD element of the design means a more compact derailleur with more direct cable routing and a more consistent direction from derailleur to gears throughout the gear range – all aimed at quicker more precise changing than previous designs. Sharp, high quality Tektro V brakes allow stopping on a sixpence, too. 


Despite the undoubted speed and outstanding performance the BYB can be adjusted to make it an extremely comfortable bike to ride and the low step-over height means it should appeal to older riders just as much as young speedsters. 


My main niggle was that the road-oriented gear range that felt a little narrow (or at least too highly geared) for a not particularly fit rider like me confronted with a steep hill. Conversely, the relatively small-spaced rear cassette allied with the large tooth front chain ring should give very impressive speed on the flat and over moderate terrain. A dealer might be able to alter the gear range for easier pedalling.

Anchor bolt locking with release lever.j



The S11 price tag of  £2200 against £1200 for the P8 is accounted for by the use of much lighter and higher quality parts in a number of areas. Whether it is worth paying it so save some 1.6kg in weight really is up to the individual’s needs from a folder and the depth of their pockets.




The Tern BYB S11 is a great addition to the choice of folders out there, and a genuinely novel addition to the annals of folding bike design.

Richard Peace




Ryton On Dunsmore

Coventry  CV8 3FH


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