A folding bicycle is a bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

 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 onto public transportation (facilitating mixed-mode commuting

Mixed-mode commuting

Mixed-mode commuting refers to the practice of using two or more modes of transportation. The goal of mixed-mode commuting is often to combine the strengths of various transportation options.-Mass transit:...

) or 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.

Variations include bikes that separate into pieces rather than fold (also called break-away models), as well as recumbent

Recumbent bicycle

A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons; the rider's weight is distributed comfortably over a larger area, supported by back and buttocks...

 and tandem

Tandem bicycle

The tandem bicycle or twin is a form of bicycle designed to be ridden by more than one person. The term tandem refers to the seating arrangement , not the number of riders. A bike with two riders side-by-side is called a sociable.-History:Patents related to tandem bicycles date from the late 19th...

s.

History

Military interest in bicycles arose in the 1890s, and the French Army and others deployed folding bikes for bicycle infantry

Bicycle infantry

Bicycle infantry are infantry soldiers who maneuver on battlefields using bicycles. The term dates from the late 19th century, when the "safety bicycle" became popular in Europe, the United States and Australia. Historically, bicycles lessened the need for horses, fuel and vehicle maintenance...

 use. In 1900, Mikael Pedersen

Mikael Pedersen

Mikael Pedersen was a Danish inventor much associated with the English town of Dursley. He is chiefly known today for the highly distinctive Pedersen bicycle...

 developed a folding version of his Pedersen bicycle

Pedersen bicycle

The Pedersen bicycle, also called the Dursley Pedersen bicycle is a bicycle that was developed by Danish inventor Mikael Pedersen and produced in the English town of Dursley. Though never hugely popular, they enjoy a devoted following and are still produced today...

 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

Second Boer War

The Second Boer War was fought from 11 October 1899 until 31 May 1902 between the British Empire and the Afrikaans-speaking Dutch settlers of two independent Boer republics, the South African Republic and the Orange Free State...

.

The British WWII Airborne BSA

Birmingham Small Arms Company

This article is not about Gamo subsidiary BSA Guns Limited of Armoury Road, Small Heath, Birmingham B11 2PP or BSA Company or its successors....

 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 bicycle was used by British paratroopers at the D-Day landings and at the Battle of Arnhem

Battle of Arnhem

The Battle of Arnhem was a famous Second World War military engagement fought in and around the Dutch towns of Arnhem, Oosterbeek, Wolfheze, Driel and the surrounding countryside from 17–26 September 1944....

. The bicycle was full-sized, and folding features included wingnuts and hinges for folding the frame, a wingnut for turning the handlebars, and reversible pedals.

Performance

Intended for commuter and utility purposes, folding bikes emphasize ruggedness, comfort and convenience, though there are high-end models that emphasize speed.

Design constraints that allow a small folded package, such as small wheels

Small wheel bicycle

Small wheel bicycles are adult bicycles which have wheels of 20 inch nominal diameter or less, which is smaller than the 26" or 700c sizes common on most full-sized adult bikes. While many folding bicycles are small wheel bicycles, not all small wheel bicycles can fold...

 and a shorter wheelbase may give a more rough, 'twitchy' ride. To compensate, folders often feature wider tires

Bicycle tire

A bicycle tire is a tire that fits on the wheel of a bicycle, unicycle, tricycle, quadracycle, bicycle trailer, or trailer bike. They may also be used on wheelchairs and handcycles, especially for racing...

 and may offer front or rear suspension

Bicycle suspension

A bicycle suspension is the system or systems used to suspend the rider and all or part of the bicycle in order to protect them from the roughness of the terrain over which they travel...

.

Folding bicycles present challenging structural compromises. They often fold near the frame mid-point (which may weaken or flex) or have elongated seatpost

Seatpost

A bicycle seatpost, seatpin, saddlepole, saddle pillar, or saddle pin is a tube that extends upwards from the bicycle frame to the saddle. The amount that it extends out of the frame can usually be adjusted, and there is usually a mark that indicates the minimum insertion...

s and stem

Stem (bicycle part)

The stem is the component on a bicycle that connects the handlebars to the steerer tube of the bicycle fork. Sometimes called a goose neck, a stem's design belongs to either a quill or threadless system, and each system is compatible with respective headset and fork designs:-Quill vs...

s which may experience greater bending stresses

Bending Moment

A bending moment exists in a structural element when a moment is applied to the element so that the element bends. Moments and torques are measured as a force multiplied by a distance so they have as unit newton-metres , or pound-foot or foot-pound...

. To compensate, folders may weigh more and have more substantial or additional frame members.

Size

Folding 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

Bottom bracket

The bottom bracket on a bicycle connects the crankset to the bicycle and allows the crankset to rotate freely. It contains a spindle that the crankset attaches to, and the bearings that allow the spindle and cranks to rotate. The chainrings and pedals attach to the cranks...

, 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

Bicycle and motorcycle geometry

Bicycle and motorcycle geometry is the collection of key measurements that define a particular bike configuration. Primary among these are wheelbase, steering axis angle, fork offset, and trail...

 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. the Montague Corporation and Dahon.

The A-bike

A-bike

The A-bike is a type of folding bicycle invented by Sir Clive Sinclair in the United Kingdom and released on 12 July 2006. It weighs and folds to 67×30×16 cm, small enough to fit in a rucksack....

 is similar to the Strida

Strida

Strida is a portable, belt-driven, folding bicycle with a distinctive 'A'-shaped collapsible frame, designed by UK engineer and designer Mark Sanders...

 but has tiny wheels and compacts a bit smaller. Bikes smaller than a Brompton are often called portable bicycle

Portable bicycle

A portable bicycle is a bicycle that has been designed to be small and light enough for easy carrying. It is usually dismantled to make a convenient bundle and the frame often has a folding action to facilitate this. The design of a portable bicycle involves a trade-off between easy of carrying...

s. They forgo the performance and easy ride benefits of their larger counterparts, acquiring characteristics similar to those of an adult folding kick scooter

Kick scooter

A kick scooter or push scooter, originally scooter, is a human-powered vehicle with a handlebar, deck and wheels that is propelled by a rider pushing off the ground. The most common scooters today have two hard small wheels, are made primarily of aluminium and fold for convenience...

. Regardless of how each folds, the result is easier to transport and store than a traditional bicycle.

Folding methods

Folding mechanisms are highly variable.

Half or mid fold Many folding frames follow classic frame pattern of the safety bicycle

Safety bicycle

A safety bicycle is a type of bicycle that became very popular beginning in the late 1880s as an alternative to the penny-farthing or ordinary and is now the most common type of bicycle. Early bicycles of this style were known as safety bicycles because they were noted for, and marketed as, being...

'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

Swift Folder

The Swift Folder is a folding bicycle, designed by Peter Reich of Design Mobility Inc. of Brooklyn, New York, in collaboration with Jan VanderTuin of the Center for Appropriate Transport in Eugene, Oregon....

 and Bike Friday

Bike Friday

Bike Friday is a brand of folding bicycle made by Green Gear Cycling of Eugene, Oregon, United States. Cyclists often refer informally to the company as Bike Friday.-Hardware:...

. Such a flip hinge may be combined with a folding front fork as in the Birdy

Birdy (bicycle)

The Birdy is a folding bicycle designed by Riese und Müller and produced by Pacific Cycles. As of 2010 over 100,000 had been sold.Released in 1995, it was the first fully suspended folding bike. The ride is regarded by some as more sporty than the Brompton, thanks in part to a stiff single-piece...

. Swing and flip hinges may be combined on the same frame, as in Brompton

Brompton Bicycle

Brompton Bicycle is a manufacturer of folding bicycles based in Brentford, London.The Brompton folding bicycle and accessories are the company's core product, noted for its self-supporting compact size when stored. All available models of the folding bicycle are based on the same hinged bicycle...

 and Dahon

Dahon

Dahon is the world's largest manufacturer of folding bicycles with a two-thirds marketshare in 2006. The company was founded by David T. Hon, a former laser physicist, in 1982 and is headquartered in Los Angeles, California, with assembly factories in China, Macau and Bulgaria...

, 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

Tikit

The tikit is a 16-inch wheel folding bicycle with an unusually fast folding mechanism that can be folded/unfolded in less than five seconds. The tikit is manufactured in the USA by Bike Friday.-Specifications:...

, featuring a cable-activated folding mechanism requiring no quick releases or latches, for increased folding speed.

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

Bicycle Torque Coupling

An S and S Coupling also known as a Bicycle Torque Coupling or BTC is a coupling which enables bicycle frames to be separated into smaller pieces, usually to facilitate packing and transporting. They can be built into the frame by the frame manufacturer when the frame is originally assembled or...

 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

Strida

Strida is a portable, belt-driven, folding bicycle with a distinctive 'A'-shaped collapsible frame, designed by UK engineer and designer Mark Sanders...

 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

Step-through frame

A step-through frame is a type of bicycle frame, often used for utility bicycles, with a low or absent top tube or cross-bar....

 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

Montague Bikes

Montague is a manufacturer that designs and produces full-size folding bicycles for civilian and potential military customers.- History :Montague Corporation was formed in 1987 by David Montague, while in graduate school at the Massachusetts Institute of Technology...

 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.

Usage

Folding bicycles are particularly suitable for urban commuters

Bicycle commuting

Bicycle commuting is the use of a bicycle to travel from home to a place of work or study — in contrast to the use of a bicycle for sport, recreation or touring....

. Mixed-mode commuters

Mixed-mode commuting

Mixed-mode commuting refers to the practice of using two or more modes of transportation. The goal of mixed-mode commuting is often to combine the strengths of various transportation options.-Mass transit:...

 who deploy the fold mechanism several times daily for portage aboard public transport may prioritize a bike with an easy, quick fold. Marine users, seeking a bike for incidental shore mobility, may prioritize the compactness of the folded bike. Riders using their bikes less frequently may prioritize speed and comfort of ride over ease and quickness of folding. People who live in a small apartment often prefer a folder as it can be more conveniently stored indoors than a full-sized bicycle.

Portability

As folded bikes require less space, they are allowed by some public transportation systems, e.g., Transport for London

Transport for London

Transport for London is the local government body responsible for most aspects of the transport system in Greater London in England. Its role is to implement the transport strategy and to manage transport services across London...

, which allows folding bikes to be carried at any time on buses and Underground

London Underground

The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...

lines. Other public transportation systems may ban or restrict other bicycles, or may require that folding bicycles be enclosed in bags or covers to protect other passengers. Some may restrict folding bikes to off rush-hour periods. Covers range from custom made bags, to bin-liners and shopping bags for smaller folders. Airline baggage regulations may permit folding bikes as ordinary luggage, without extra cost.