Brompton Bicycle

The elements which allow the fold to work are:

• a pivoting rear triangle, allowing the length to be shortened, while keeping the chain in the same alignment. There is a slight arch in the main frame to allow the wheel to swing under to the parked position;
• derailleur gear models have a chain tensioner arm capable of swinging through a wide arc, in order to control the full length of the chain during folding without the chain coming loose. In the folded position the chain is looped back on itself;
• small wheels on top of the rear mud guard or carrier to allow the folded bike to be rolled;
• a main frame hinge in the centre of the bicycle allows the front wheel to be swung around and placed against the rear wheel. As the front wheel swings freely (for steering), the front wheel remains pointing forwards when folded;
• a handlebar stem with the hinge placed at 45 degrees to the rest of the bicycle allowing handlebars to swing through 180 degrees and lie parallel with the wheels when folded;
• a seat post combining variable height adjustment and locking. When lowered during folding, the base of the post locks against the lower stop disc preventing the folded package from swinging open;
• a folding pedal on the left-hand side.

The final folded package is 565 × 545 × 250 mm (22.2 × 21.5 × 9.8 in) if the standard, rather than longer, seat post is used, and weighs between 9 and 12.5 kg (20 to 28 lb) depending on the configuration. The standard saddle of 2009 and later models acts as a carrying handle for the folded bike, with finger-grip ridges on the underside. With practice, folding and unfolding takes 10 to 20 seconds.

The basic model code has a letter to describe the handle bar type, the number of gears, and a letter for factory-attached fixtures. A suffix is appended to indicate titanium partss. For example model "M3R" has classic "M" handle bars, "3" gears (using a hub gear) and has a rear rack, "R" . If some titanium parts are used, the code becomes  "M3R-X". An exception is the B75, a budget model launched in April 2019 to commemorate Brompton's founding in 1975,[18] using the M3E configuration with some components drawn from a stock of older parts.

Different colour folded Brompton Bicycles in New York. Half retain their supplied stock saddle

All models with a rack may have the wheels on the corners of the rack replaced with larger "eazy wheels", to aid pushing when folded and to give greater heel clearance than the stock rollers. All models can have no built-in lights, battery lights, or two variants of front wheel hub dynamo. The standard seat post can be replaced by a longer or telescopic steel post for taller riders. Bicycles are available in black, white, orange and cobalt blue as standard;[19] other colours, raw lacquer, and titanium are available at extra cost. Titanium areas are left unpainted. The standard Brompton saddle can be substituted by a Brooks B17 Special leather saddle in ladies' or men's versions. Non-titanium models have braze-on fittings for holding the supplied Zefal HP compact high-pressure pump.

A front luggage block may be fitted to the frame of all models to support a compatible bag (fitting to the forks or handle bars interferes with steering). Hub dynamo models have a special thin Schmidt Maschinenbau SON XS dynamo fitted at the centre of the front wheel, or a cheaper Shimano dynamo. Until 2009 tyre dynamos were used for standard permanent lighting.

A full "superlight" variant uses titanium to reduce weight, and has lighter wheel components. The rear triangle and front forks are titanium, and some smaller parts are titanium or aluminium. The main frame is steel. This more expensive version may weigh less than ten kilograms. Titanium models do not have a pump mounting, saving approximately 75 grams (2.6 oz).

Tyres may be kevlar-based puncture-resistant Brompton-branded tyres, lighter, faster Schwalbe Kojak, or more robust and puncture-resistant Schwalbe Marathon. Raleigh Record tyres were standard until the 2000s. Aftermarket tyres include the Schwalbe Marathon Plus, a heavy but very puncture-resistant model although Brompton states that this is not recommended officially.

P handlebar

Detail of the folding pedal

A small saddle bag can be fitted behind the saddle for the Brompton cover and any tools or spares. Most of the handlebar types can also accommodate standard handlebar bags.

When fitted with a front luggage block, various bags may be fitted: a folding basket, large touring pannier (T-bag), two variants of bicycle-messenger style flip-over bag (the S- or the larger C-bag), a waterproof option by Ortlieb, a Carradice "City Folder" cotton duck canvas bag, or a leather attaché case (the A-bag). These bags all have the same internal luggage frame, which can also be used separately. Some accessories are made by other companies for Brompton bicycles.

Many design changes can be retrofitted on earlier models. An exception is that in 2004 the frame was changed, with a longer wheelbase.

Handlebar stem hinge

switched to a jig-brazed system

Handle-bar clip

reinforced wire clip providing increasing gripping to secure the handle-bar stem when folded down.

Handlebars

Two alternative handlebar designs; the original handlebar being redesignated as the 'M' type.

Frame

The wheelbase was lengthened in 2004. Frames made before 2004 do not accommodate the Brompton Toolkit, nor the new design pump.[20]

Titanium parts

saving approximately 1 kilogram combined[21]

Dual action calliper brakes

later fitted as standard to both the front and back wheels

Wide range hub

Brompton Wide-Range (BWR) hub with a wider gear ratio spacing, more suited to the Brompton's smaller wheel size, since 2008[22]

Non-folding pedal

new right-hand non-folding pedal designed to increase robustness and balance the folding pedal.

notch added to prevent over folding of left-hand folding pedal

Upright handlebar

since 2012 Handlebar style "H"

Integrated bell+brake+shifter on 2017 'M'/'H'-handlebar

Several changes were made from November 2016. The 'M' and 'H' handlebars now had Brompton integrated brake + bell + shifter + gear units hung below the handlebar. The handlebars retained the same overall height, but with a 20mm higher stem and smoother curve. The 'M', 'H' and flat 'S' handlebars switched to using longer and removable handlebar grips.[23]

New guides and rollers on redesigned 2017 rack

The design of the rear rack casting changed, with the new design incorporating two cut-outs for the built-in luggage straps.

In August 2017 Brompton introduced an electric bicycle in the U.K.[24]

Further modifications are provided by some Brompton dealers or skilled individuals, the most prominent examples being:

Rear hub

The Brompton's frame fits rear hubs with an over locknut dimension (OLD) of 115 mm. Many rear hubs on the market, however, are 135 mm wide (which is the standard used by full-size and folding bicycles) and so do not fit without modifying the frame. A notable exception is Sturmey Archer's 8-speed hub X-RF8 which is available in 120 mm width[25] and can fit the Brompton with only little modification.

• Vintage Sturmey-Archer medium or close-ratio internals, which can be screwed straight into the OEM hub shell
• Other additions need a modified frame which is available from third party manufacturers:[26]
  • Disc brakes
  • Shimano Nexus seven- eight- or eleven-speed hubs.
  • Fourteen-speed Rohloff Speedhub.

Rear axle

Derailleur gears either in addition to, or instead of the standard internal hub gearing

Bottom bracket

• Schlumpf Drive: Fitting a Schlumpf Mountain Drive to the bottom bracket to give a selectable 2.5x reduction ,[27] ( also Schlumpf High Speed Drive to give a selectable 2.5x increase , effectively giving the same range as the Mountain Drive with a much smaller chainwheel ) thereby doubling the number of gears available to two-, four-, six-, or twelve-speeds
• Additional front derailleur chain-rings as from on a mountain bike
• Oversize, or elliptical ("egg") rings giving higher possible top-speeds for extremely fit riders

Front wheel hub

• Disk Brakes
  • Front Forks Need modifications
• Electric motor, combined with a battery bank attached to either the rear rack, or stored in the front pannier
• Pantour suspension hub
• Dynamo hubs. Brompton now offer a narrow-width SON XS or alternatively a Shimano dynamo hub as standard factory-supplied upgrades

Luggage

• Custom-made luggage using the Brompton luggage frame
• Rear luggage attached to the seat-post

Contact points

• Leather or other handlebar grips; replacements need to be approximately 95-100mm wide compared to 130mm for other bicycles
• Upgraded saddles: Brompton offer a branded Brooks B17, but any saddle can be fitted if the Brompton "Pentaclip" adapter is used

Brompton owners and designers with suitable engineering expertise have tried to improve the design, although there is limited scope to do so as any additions attached are likely to compromise either the final folded size, carried weight or folding action.

• "SP". In the United Kingdom, builder Steve Parry specialises in producing a range of customised bicycles designated SP, which are based on the Brompton and use many Brompton components. Typically, these machines might combine a seven-speed derailleur or the 14-speed Rohloff Speedhub, V-brakes, carbon fibre seat post and a suspension handlebar system, although the exact specifications will often be agreed with the purchaser prior to building.
• "Brekki" recumbent upgrade kit. A collection of add-ons formerly offered by a German cyclist, Juliane Neuß, to convert a basic Brompton into a recumbent bicycle design at the cost of a larger folded package and heavier weight.[28] The kit does not fit the current Brompton, which has a longer main frame.
• Ultimate Folding Bicycle. Leonard Rubin's on-going development (in Portland, Oregon) involving wholesale replacement of virtually all original Brompton frame components with titanium or lightweight versions. The result is a sub 8-kilogram bicycle with a Brompton fold and luggage compatibility.[29]
• "Nano Brompton" an upgrade to convert a basic Brompton to an electric bike by adding a front 250-watt 2-kilogram electric hub motor. The battery pack is either mounted on the handlebars, or using contact strips embedded in a modified front carrier block.[30]
• "Brompton E-Freedom" – an upgrade to convert a basic Brompton to an electric bike by adding a powerful electric front hub motor to the Brompton, with nano-technology batteries, the whole kit (incl motor, battery, controller & throttle) adds only 3.2 kg to the overall bike's weight.[31]

In 1992, Brompton agreed with Euro-Tai in Taiwan to allow the manufacture of a licensed copy of the Brompton bicycle for distribution in Eastern Asia.[40][41] A joint venture company called Neobike was then established to manufacture them. Brompton Bicycle in the United Kingdom would loan tools and drawings, and be paid on a per-unit royalty basis.

By mid-1992, Neobike had recruited three senior research and development employees from Dahon, another folding bicycle company, and had started to produce other designs and copies in addition to the official Brompton design. Brompton's licensing contract with Euro-Tai/Neobike lasted approximately ten years until it expired on 31 December 2002. By this time, five senior Neobike employees had been convicted and jailed for stealing trade secrets from Dahon and Ritchie had previously stated that the franchise contract had been "under review",[42] there having been quality issues with the Asian-built Brompton bicycles.[43] Euro-Tai and Neobike failed to return the Brompton-specific tooling loaned by Brompton Bicycle.[44] One week later after the expiration of the official licensing agreement Euro-Tai sold its controlling stake in Neobike to YTE Manufacturing, an aluminium supplier that was already involved with producing frames for Neobike.[45]

At the 2003 Eurobike trade show, Neobike exhibited their—now unsanctioned—clone of the Brompton, offering it to potential dealers within Europe. Neobike-produced copies of the Brompton bicycle were then imported into The Netherlands branded as the "Scoop One" and "Astra Flex V3".[46] Later, Neobike's interests in its copy-bicycle business were transferred to an entity called Grace Gallant Enterprises,[44] for sale under the brand "Flamingo". Between 2004 and 2010, several batches of copies were imported into the European market: into the United Kingdom under the name "Merc", into Belgium, and into Spain as the "Nishiki Oxford". Taiwanese-manufactured clones bear the model numbers FL-BP01-3/FL-BP01-7 standing for Flamingo, "Best Persuader", 3-speed/7-speed. As of 2014, Grace-Galant continue to make clones for the East Asia market under the Flamingo and MIT brand names. Later iterations of the clones had their frames made of aluminium, rather than the steel frame of the originals.

Following the expiry of the Brompton patent,[47] Brompton Bicycle's legal actions against Neobike/Grace Gallant have all been brought on the basis of copyright- and industrial design-law.

A court case was held at the Groningen civil court in the Netherlands on 24 May 2006, which ruled that the industrial design of the Brompton folding bicycle was protected by copyright. Additionally, the Neobike-provided manual had included direct copies of those drawings found in the Brompton user manual.[48] The Brompton Bicycle Limited v Rijwielbedrijf Vincent Van Ellen BV ruling held that there was creative flexibility in the design for a bicycle beyond those choices made purely for functional reasons; in the Brompton case this included the M-style handlebars, curved main frame tube and the cable-placement.[48] Each of these were noted to be distinctive design decisions that another manufacturer could change without compromising the ability to create a functional folding bicycle. Such a level of perceived similarity was therefore likely to cause "confusion in the market" under the Dutch copyright law, Article 13. Neobike did not choose to appeal and Brompton Bicycle was granted the right to have all of the imported bicycles destroyed with an injunction against future imports by Neobike's distributors.[48][46]

In June 2010, Brompton Bicycle gained a further injunction against the import of the unlicensed copy Brompton models into Spain, this time under the name "Nishiki Oxford Bicycle". The case was decided on the basis that Grace Gallant predecessors' had not returned all of Brompton Bicycle Ltd's drawing and toolings upon the termination of the earlier Eurotai/Neobike franchise agreement.[44]

Brompton Bicycle has used various social networking sites for brand promotion.