What is a Folding Bike?A folding bicycle is a bicycle designed to fold into a compact form, facilitating transport and storage. When folded, the bikes can be more easily carried into buildings and workplaces or on public transportation (facilitating mixed-mode commuting and bicycle commuting, and more easily stored in compact living quarters or aboard a car, boat or plane.
Folding mechanisms vary, with each offering a distinct combination of folding speed, folding ease, compactness, ride, weight, durability and price. Distinguished by the complexities of their folding mechanism, more demanding structural requirements, greater number of parts, and more specialized market appeal, folding bikes may be more expensive than comparable non-folding models. The choice of model, apart from cost considerations, is a matter of resolving the various practical requirements: a quick easy fold, compact folded size, or a faster but less compact model.
There are also bicycles that provide similar advantages by separating into pieces rather than folding.
A Brompton folding bicycle
Folded Brompton, side viewHistoryMilitary interest in bicycles arose in the 1890s, and the French army and others deployed folding bikes for bicycle infantry use. In 1900, Mikael Pedersen developed a folding version of his Pedersen bicycle for the British army that weighed 15 pounds and had 24 inch wheels. It included a rifle rack and was used in the Second Boer War.
The British WWII Airborne BSA folding bicycle was used from 1939-1945 in the Second World War by British paratroopers. A folding bicycle was developed as a small size was needed to enable it to be taken on parachute jumps from aircraft. The War Office in 1941 called for a machine that weighed less than 23lb and which would withstand being dropped without protection by parachute. BSA abandoned the traditional diamond design as too weak for the shockn and made an elliptical frame of twin parallel tubes, one forming the top tube and seat stays and the other for the chainstay and down tube. The hinges were in front of the bottom bracket and in the corresponding position in front of the saddle, fastened by wing nuts. The pedals could be reversed to avoid snagging. The frame weighed 4¾lb.
The bicycle was used by British paratroopers at the D-Day landings and at the Battle of Arnhem.
Italian Bersaglieri during World War I with folding bicycles strapped to their backs. 1917.SizeFolding bikes generally come with a wider range of adjustments than conventional bikes for accommodating different riders, because the frames are usually only made in one size. Seatposts and handlebar stems on folders extend as much as four times higher than conventional bikes. For even greater range of adjustment, longer after-market posts and stems are available. While folding bicycles are usually smaller in overall size than conventional bicycles, the distances between center of bottom bracket, the top of the saddle and the handlebars, the primary factors in determining whether a bicycle fits its rider, are usually similar to that of conventional bikes. The wheelbase of many folding designs is also very similar to that of conventional, non-folding, bicycles. Some manufacturers are producing folding bikes designed around folding systems that allow them to use 26" wheels, e.g. Montague, KHS and Dahon Bicycles.
The A-bike is similar to the Strida but has tiny wheels and compacts a bit smaller. Bikes smaller than a Brompton are often called portable bicycles. They forgo the performance and easy ride benefits of their larger counterparts, acquiring characteristics similar to those of an adult folding kick scooter. Regardless of how each folds, the result is easier to transport and store than a traditional bicycle.
Shaft-driven folding bikeFolding MethodsFolding mechanisms are highly variable.
Half or mid fold Many folding frames follow classic frame pattern of the safety bicycle's diamond frame, but feature a hinge point (with single or double hinges) allowing the bicycle to fold approximately in half. Quick-connect clamps enable raising or lowering steering and seat columns. A similar swing hinge may be combined with a folding steering column. Fold designs may use larger wheels, even the same size as in non-folders, for users prioritizing ride over fold compactness.
Triangle hinge A hinge in the frame may allow the rear triangle and wheel to be folded down and flipped forward, under the main frame tube, as in the Swift Folder and Bike Friday. Such a flip hinge may be combined with a folding front fork as in the Birdy. Swing and flip hinges may be combined on the same frame, as in Brompton and Dahon, which use a folding steering column. Folding mechanisms typically involve latches and quick releases, which affect the speed of the fold/unfold. Bike Friday offers a model, the Tikit, featuring a cable-activated folding mechanism requiring no quick releases or latches, for increased folding speed.[8]
Break away and other styles Bikes may partly fold and partly disassemble for packing into a standard or custom sized suitcase for air travel (e.g., Airnimal and Bike Friday). Other variations include the bicycle torque coupling is a proprietary connector system that can be retrofitted to a standard frame. The Giatex folds and retracts, adjusting to the size of the rider. The Gekko folds from the seat tube like an upside down umbrella. The iXi literally breaks into 2 halves. The Strida has a triangular frame and folds to resemble a unicycle.
Folding mechanisms may incur more cost and weight, allow folding smaller, and tend to use smaller wheels. 24 inch wheels are the largest for which flip hinges are generally used, but smaller wheels, typically 16 or 20 inches, are more common. Smaller size does not mean lighter weight, as most of these designs forgo the bracing benefits of the diamond frame, and must compensate as a step-through frame does, with thicker metal. The step-through design is a boon to a wider range of rider size, age and physical ability. Another system found on folders such as Montague Bikes utilizes the seat tube as a pivot point for the frame to fold. This system uses a tube within a tube design to give the bike more torsional stiffness. It allows the user to fold the bike without "breaking" any vital tubes down, preserving the structural integrity of the diamond frame. This system is operated by a single quick release found along the top tube of the bike.
Overlaid photos of two KHS bicycles, one a F20 20" wheel folding bicycle and the other a Flite 100 700c wheel racing bike, showing similarities in the geometry and riding position
1960s European folding bicycle, showing hinged frame, height adjustable seat post, and quick release handlebar stem allowing the bars to turn parallel to the frame when foldedPortabilityMany public transportation systems ban or restrict unfolded bicycles, but allow folded bikes all or some of the time. For example Transport for London allows folding bikes to be carried at any time on buses and Underground lines, but allows unfolded bicycles on Tube trains only outside of peak times, and then only on lines that do not have escalator access. Some transport operators only allow folding bicycles if they are enclosed in a bag or cover. Airline baggage regulations often permit folding bikes as ordinary luggage, without extra cost.
Notable folding bicycles include:
A-bike
Bike Friday
Birdy
Bridgestone Picnica
Brompton Bicycle
Dahon
KHS Bicycles
Melon Bicycles
Montague Bikes
Raleigh Twenty
Schwinn
Strida
Swift Folder
Tern Bicycles
Tikit