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A motorcycle frame is a motorcycle's core structure. It supports the engine, provides a location for the steering and
rear suspension Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding/ handling and ride q ...
, and supports the rider and any passenger or luggage. Also attached to the frame are the fuel tank and battery. At the front of the frame is found the steering head tube that holds the pivoting front fork, while at the rear there is a pivot point for the
swingarm A swingarm, or "swinging arm" (UK), originally known as a swing fork or pivoted fork, is a single or double sided mechanical device which attaches the rear wheel of a motorcycle to its body, allowing it to pivot vertically. The main component of ...
suspension motion. Some motorcycles include the engine as a load-bearing stressed member; while some other bikes do not use a single frame, but instead have a front and a rear subframe attached to the engine.


Materials

In the early days, motorcycles were little more than motorised
bicycle A bicycle, also called a pedal cycle, bike or cycle, is a human-powered or motor-powered assisted, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A is called a cyclist, or bicyclist. Bic ...
s, and consequently frames were tubular steel. While the use of steel tubing is still common, in modern times other materials, such as titanium,
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...
, magnesium, and
carbon-fibre Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...
, along with composites of these materials, are now used. As different motorcycles have varying design parameters (such as cost, complexity, weight distribution, stiffness, power output and speed), there is no single ideal frame design, and designers must make an informed decision of the optimum choice.


Steel

In Europe and the USA, steel tubing was the default material until recent times. All the major manufacturers (AJS, Ariel, BSA, Matchless, Norton, Sunbeam, Triumph, Velocette, BMW, DKW, Ducati, Moto-Guzzi, Harley-Davidson and Indian) used steel tubing. ;Examples *
Norton Norton may refer to: Places Norton, meaning 'north settlement' in Old English, is a common place name. Places named Norton include: Canada * Rural Municipality of Norton No. 69, Saskatchewan * Norton Parish, New Brunswick **Norton, New Brunswick, ...
Featherbed frame The featherbed frame was a motorcycle frame invented by the McCandless brothers and offered to the British Norton motorcycle company to improve the performance of their racing motorcycles in 1950. It was considered revolutionary at the time,"'' ...
*Most Ducati Motorcycles *
Honda CB750 The Honda CB750 is an air-cooled, transverse, in-line four-cylinder engine motorcycle made by Honda over several generations for year models 1969–2003 as well as 2007 with an upright or standard riding posture. It is often called the original ...


Aluminium

Unlike the development seen in bicycle frames where tubular steel frames were succeeded by frames welded out of round or ovalized aluminium tubing, the aluminium in motorcycle frames is almost exclusively welded in more angular forms, and often forming a monocoque frame. ;Examples *
Honda VFR750 The Honda VFR750F is a motorcycle manufactured by Japanese automobile manufacturer Honda from 1986 to 1997. The model was initially displayed to the press after the 1985 Bol d'Or before it was officially introduced in 1986. The motorcycle is ...
*
Yamaha YZF-R1 The Yamaha YZF-R1, or simply R1, is a -class sports motorcycle made by Yamaha. It was first released in 1998, undergoing significant updates in 2000, 2002, 2004, 2006, 2007, 2009, 2015, 2018


Carbon fibre

In 1983, Armstrong motorcycles produced a 250cc
Grand Prix Grand Prix ( , meaning ''Grand Prize''; plural Grands Prix), is a name sometimes used for competitions or sport events, alluding to the winner receiving a prize, trophy or honour Grand Prix or grand prix may refer to: Arts and entertainment ...
motorcycle using a revolutionary
carbon fiber Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...
frame. Following the technology being used by the Formula One industry, Armstrong designers Mike Eatough and Barry Hart created the first motorcycle using a carbon fiber frame to compete in Grand Prix racing. ;Examples *
Ducati Desmosedici The Ducati Desmosedici is a four-stroke V4 engine racing motorcycle made by Ducati for MotoGP racing. The series nomenclature is ''GP'' with the two-digit year appended, such as Desmosedici GP10 for 2010. In 2006 Ducati made a short production r ...
* MotoCzysz C1


Magnesium

;Examples *
1988 File:1988 Events Collage.png, From left, clockwise: The oil platform Piper Alpha explodes and collapses in the North Sea, killing 165 workers; The USS Vincennes (CG-49) mistakenly shoots down Iran Air Flight 655; Australia celebrates its Bicentenn ...
Elf ROC- Honda Elf5-
NSR500 Japanese Grand Prix 1993 ">1993 Japanese motorcycle Grand Prix">Japanese Grand Prix 1993 The Honda NSR500 is a road racing motorcycle created by HRC (Honda Racing Corporation) and debuted in 1984 for the Grand Prix motorcycle racing's 500&nb ...
500 cc
Grand Prix Grand Prix ( , meaning ''Grand Prize''; plural Grands Prix), is a name sometimes used for competitions or sport events, alluding to the winner receiving a prize, trophy or honour Grand Prix or grand prix may refer to: Arts and entertainment ...


Titanium

;Examples *1971 Titanium Husqvarna Inter-
AMA Ama or AMA may refer to: Ama Languages * Ama language (New Guinea) * Ama language (Sudan) People * Ama (Ama Kōhei), former ring name for sumo wrestler Harumafuji Kōhei * Mary Ama, a New Zealand artist * Shola Ama, a British singer * Ām ...
Motocross Motocross is a form of off-road motorcycle racing held on enclosed off-road circuits. The sport evolved from motorcycle trials competitions held in the United Kingdom. History Motocross first evolved in Britain from motorcycle trials competit ...


Composite

;Examples *
Bimota SB8K The SB8K is a sportbike made by Italian motorcycle manufacturer Bimota. The bike was added to the present lineup after the company hiatus in the late 1990s financial crisis. The bike was built with a profusion of light alloys and carbon fiber; th ...
, composed of two aluminium alloy beams and carbon fibre plates * MV Agusta F4 750 Serie Oro, magnesium and aluminium * Greeves 250DCX Sportsman, with cast alloy "downtube", tubular steel rear subframe and semi-monocoque spine.


Types


Spine or backbone

The motorcycle engine is suspended from a single spine. Spine could be a solid structure. ;Examples * Honda CB92 Benly * MZ TS250 * Honda CB600F Hornet


Single cradle

The motorcycle engine is held in a single cradle with a single spine. Examples * Honda CG125


Half-duplex cradle or double cradle

The motorcycle engine is held in a double cradle with a single spine and single downtube. ;Examples *
Honda CB1000 The Honda CB1000 Super Four is a CB series standard motorcycle made by Honda is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan. Honda h ...
* Suzuki TS50ER


Full duplex cradle

The motorcycle engine is held in place within a pair of separate cradles. The Norton
Featherbed frame The featherbed frame was a motorcycle frame invented by the McCandless brothers and offered to the British Norton motorcycle company to improve the performance of their racing motorcycles in 1950. It was considered revolutionary at the time,"'' ...
was the classic example, but many "duplex" frames actually have a single spine beneath the tank. ;Examples *
Norton Manx The Norton Manx or Manx Norton is a British racing motorcycle that was made from 1947 to 1962 by Norton Motors Ltd. Norton had contested every Isle of Man TT race from the inaugural 1907 event through into the 1970s, a feat unrivalled by any ...
* Suzuki TS50X


Perimeter

Also called beam or twin spar, two beams wrap around the engine to join the steering head and swing arm in the shortest distance possible for better rigidity. Beams are usually made of pressed metal (steel/aluminium). The trellis frame employs the same concept but uses welded members to form a trellis instead of pressed metal.
Antonio Cobas Antonio Cobas (Barcelona 1952 – April 14, 2004) was a Spanish Grand Prix motorcycle designer, constructor and mechanic who built world championship winning motorcycles. Cobas was credited with being the originator of the modern, aluminum frame ch ...
is credited with pioneering the modern, aluminum perimeter frame chassis now used on many modern racing and production motorcycles. In 1982, Cobas developed a stronger and lighter aluminum twin-beam chassis to replace the steel backbone frames. The technology was copied by major motorcycle manufacturers and by the 1990s, all the major racing teams in Grand Prix competition used the aluminum frame design pioneered by Cobas. ;Examples * 1885 Daimler ''Reitwagen'' * Honda CBR1000RR * Yamaha FZR600 *
Ducati Panigale V4 The Ducati Panigale V4 is a sport bike with a desmodromic 90° V4 engine introduced by Ducati in 2018 as the successor to the V-twin engined 1299. A smaller engine displacement version complies with the Superbike category competition regulati ...


Pressed

The frame is pressed or stamped from sheet metal to form a car-type semi- monocoque. One of the earliest examples was the 965cc motorcycle produced by Louis Janoir in 1920, which used pressed steel for the frame, rear swinging arm, and the front forks. The frame may be entirely pressed (Ariel Arrow), or may have just a pressed aft section connected to the steering head by a conventional steel tubular spine (Honda Super Cub). Both the Super Cub and the Arrow also have pressed steel forks, instead of conventional telescopic forks. ;Examples * Louis Janoir 1920 965cc flat-twin *
Ariel Arrow The Ariel Leader was a British motorcycle produced by Ariel Motorcycles between 1958 and 1965. A radical design, the Leader was fully enclosed with an integral windscreen and was the first British motorcycle to have optional flashing indicators ...
*
Honda Super Cub The Honda Super Cub or Honda Cub is a Honda underbone motorcycle with a four-stroke single-cylinder engine ranging in displacement from . In continuous manufacture since 1958 with production surpassing 60 million in 2008, 87 million in 2014, an ...


Monocoque

More common in the car world, a monocoque frame comprises a structure where loads are supported through its external skin. On motorcycles they are used almost exclusively on racing motorcycles. French industrialist and engineer Georges Roy attempted in the 1920s to improve on the bicycle-inspired motorcycle frames of the day, which lacked rigidity. This limited their handling and therefore performance. He applied for a patent in 1926, and at the 1929 Paris Automotive Show unveiled his new motorcycle, the Art-Deco styled 1930 Majestic. Its new type of monocoque body solved the problems he had addressed, and along with better rigidity it did double-duty, as frame and bodywork provided some protection from the elements. Strictly considered, it was more of a semi-monocoque, as it used a box-section, pressed-steel frame with twin side rails riveted together via crossmembers, along with floor pans and rear and front bulkheads. A Piatti light scooter was produced in the 1950s using a monocoque hollow shell of sheet-steel pressings welded together, into which the engine and transmission were installed from underneath. The machine could be tipped onto its side, resting on the bolt-on footboards for mechanical access. A monocoque-framed motorcycle was developed by Spanish manufacturer Ossa for the
1967 Grand Prix motorcycle racing season Events January * January 1 – Canada begins a year-long celebration of the 100th anniversary of Confederation, featuring the Expo 67 World's Fair. * January 5 ** Spain and Romania sign an agreement in Paris, establishing full consular a ...
. Although the single-cylinder Ossa had less than its rivals, it was lighter and its monocoque frame was much stiffer than conventional motorcycle frames, giving it superior agility on the racetrack. Ossa won four Grands Prix races with the monocoque bike before their rider died after a crash during the 250 cc event at the
1970 Isle of Man TT The 1970 Isle of Man TT, the fourth round of the 1970 Grand Prix motorcycle racing season, involved a number of races on the Mountain Course on the Isle of Man. For the third consecutive year, Giacomo Agostini won both the Junior and Senior races ...
, causing the Ossa factory to withdraw from
Grand Prix Grand Prix ( , meaning ''Grand Prize''; plural Grands Prix), is a name sometimes used for competitions or sport events, alluding to the winner receiving a prize, trophy or honour Grand Prix or grand prix may refer to: Arts and entertainment ...
competition. Notable designers such as Eric Offenstadt and Dan Hanebrink created unique monocoque designs for racing in the early 1970s. The F750 event at the
1973 Isle of Man TT The 1973 Isle of Man TT was a road racing event for motorcycles held in the Isle of Man on the 37-mile Snaefell Mountain Course. It was the fifth round of the 1973 Grand Prix motorcycle racing season (now known as MotoGP). The Australian rider J ...
races was won by Peter Williams on the monocoque-framed John Player Special that he helped to design based on
Norton Commando The Norton Commando is a British Norton-Villiers motorcycle with an OHV pre-unit parallel-twin engine, produced by the Norton Motorcycle company from 1967 until 1977. Initially having a nominal ''750 cc'' displacement, actually , in 19 ...
. Honda also experimented with the NR500, a monocoque Grand Prix racing motorcycle in
1979 Events January * January 1 ** United Nations Secretary-General Kurt Waldheim heralds the start of the ''International Year of the Child''. Many musicians donate to the ''Music for UNICEF Concert'' fund, among them ABBA, who write the song ...
. The bike had other innovative features, including an engine with oval shaped cylinders, and eventually succumbed to the problems associated with attempting to develop too many new technologies at once. In 1987
John Britten John Kenton Britten (1 August 1950 – 5 September 1995) was a New Zealand mechanical engineer who designed a world-record-setting motorcycle with innovative features and materials. Biography John Britten was born to Bruce and Ruvae Britten in C ...
developed the Aero-D One, featuring a composite monocoque chassis that weighed only . An aluminium monocoque frame was used for the first time on a mass-produced motorcycle from 2000 on Kawasaki's
ZX-12R The Kawasaki Ninja ZX-12R is a motorcycle in the Ninja sport bike series made by Kawasaki from 2000 through 2006. The inline-four engine produced at low speed, and increased to at high speed due to its ram-air intake, making it the most powerf ...
, their flagship production sportbike aimed at being the
fastest production motorcycle The fastest production motorcycle for a given year is the unmodified motorcycle with the highest tested top speed that was manufactured in series and available for purchase by the general public. Modified or specially produced motorcycles are a dif ...
. It was described by ''
Cycle World ''Cycle World'' is a motorcycling magazine in the United States. It was founded in 1962 by Joe Parkhurst, who was inducted to the Motorcycle Hall of Fame as "the person responsible for bringing a new era of objective journalism" to the US. ''Cycl ...
'' in 2000 as a "monocoque backbone...a single large diameter beam" and "Fabricated from a combination of castings and sheet-metal stampings". Single-piece
carbon fiber Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...
bicycle frame A bicycle frame is the main component of a bicycle, onto which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles: a main triangle ...
s are sometimes described as monocoques; however as most use components to form a frame structure (even if molded in a single piece), these are frames not monocoques, and the pedal-cycle industry continues to refer to them as framesets. ;Examples * 2000 Kawasaki Ninja ZX-12R * 2006 Kawasaki Ninja ZX-14 * 2012
Ducati 1199 The Ducati 1199 Panigale was a Ducati sport bike introduced at the 2011 Milan Motorcycle Show. The motorcycle is named after the small manufacturing town of Borgo Panigale. Ducati had announced a larger displacement 1299 Panigale for the 2015 ...


Semi-monocoque

If a "monocoque" frame uses additional support, such as tubes or longerons, the frame is more properly called a "semi-monocoque". An example is Peter Williams' semi-monocoque Norton racer.


Trellis

A trellis frame connects the steering head to the
swingarm A swingarm, or "swinging arm" (UK), originally known as a swing fork or pivoted fork, is a single or double sided mechanical device which attaches the rear wheel of a motorcycle to its body, allowing it to pivot vertically. The main component of ...
pivot as directly as possible using metal
tube Tube or tubes may refer to: * ''Tube'' (2003 film), a 2003 Korean film * ''The Tube'' (TV series), a music related TV series by Channel 4 in the United Kingdom * "Tubes" (Peter Dale), performer on the Soccer AM television show * Tube (band), a ...
arranged in triangulated reinforcement. Using
lattice girder A lattice girder is a truss girder where the load is carried by a web of latticed metal. Overview The lattice girder was used prior to the development of larger rolled steel plates. It has been supplanted in modern construction with welded o ...
principles, a trellis frame is typically constructed of round or oval section metal tubular segments that are welded or
brazed Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from we ...
together. A well-designed trellis frame should provide a strong, lightweight structure that simplifies placement of engine and components, and gives good access for maintenance. Although construction of a trellis frame needs a more complicated process than, say, an alloy beam frame, it requires only a simple jig and a competent welder. No heavy capital outlay is required, so a trellis frame is ideal for a model that may be made in relatively small numbers. For this reason, the trellis frame has found favour with European manufacturers, and Ducati in particular. Some motorcycles, such as the Yamaha TRX850, have hybrid frames that employ alloy
casting Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejected ...
s at the swingarm pivot area. Another variation is to suspend the engine from a trellis frame, but have the
swingarm A swingarm, or "swinging arm" (UK), originally known as a swing fork or pivoted fork, is a single or double sided mechanical device which attaches the rear wheel of a motorcycle to its body, allowing it to pivot vertically. The main component of ...
pivot cast into the rear of the engine. ;Examples * Most modern Ducatis * Suzuki Bandit 400 1989 Model *
Honda VTR250 The Honda VTR250 is a 90° V-twin motorcycle produced by Honda that has had one major revision. The original VTR250 was a faired sport bike sold only in the United States and Canada from 1988 to 1990. The next VTR250 model is a naked bike, produce ...
* KTM 690 Enduro *
KTM 1290 Super Duke R The KTM 1290 Super Duke R is a 1301 cc 75° V-twin engine, naked motorcycle from the Austrian manufacturer KTM. With the update in 2017 the motor is the most powerful LC8 engine ever built by KTM. Design The KTM 1290 Super Duke R is a nak ...


Engine as a stressed member

For rider comfort, a motorcycle's engine can be mounted on rubber bushings to isolate vibration from the rest of the machine. This strategy means the engine contributes little to frame stiffness, and absorbing rather than dissipating vibration can lead to stress damage to the frame, exhaust pipes, and other parts. Instead, if the engine is rigidly mounted to the frame, vibrations pass to and are dissipated via the whole frame, and the rider. Rigid mounting allows the engine to contribute to the overall stiffness of the frame. It also becomes possible to mount the swingarm directly to the engine rather than the frame, avoiding the need for frame members extending downward to the swingarm pivot. By increasing the number of mounting points between the engine and frame, vibrations and stress can be better dissipated in the frame, typically creating a triangle between the swingarm in the rear, the cylinder head at the top and the lower crankcase area at the front. If a rigidly mounted engine not only contributes to, but is critical to, the stiffness of the frame, and is an integral part of closing the triangle or trellis structure that transfers force from the headstock to the swingarm, to the point that without the engine the frame would be deformed, the engine is called a stressed member, or a lifted engine. Sharing the load between the engine and frame reduces the overall weight of the motorcycle. Stressed member engines were pioneered at least as early as the 1916 Harley-Davidson 8-valve racer, and incorporated in the production
Harley-Davidson Model W The Harley-Davidson Model W, also known as the ''Sport Twin'', is a motorcycle made by Harley-Davidson from 1919 to 1923. Unusually for a Harley-Davidson motorcycle, the Model W had a flat-twin engine and a trailing link fork. The Model W set spe ...
by 1919. This was called a keystone, or diamond, frame. The 1946 Vincent Series B Rapide was designed with an advanced chassis, termed a "tour de force for its day," that included a stressed member engine. During early testing of the 1983
Kawasaki GPZ900R The Kawasaki GPZ900R (also known as the ZX900A or Ninja 900) is a motorcycle that was manufactured by Kawasaki from 1984 to 2003. It is the earliest member of the Ninja family of sport bikes. The 1984 GPZ900R (or ZX900A-1) was a revolutionary des ...
, twin downtubes were included, creating a full cradle, but the downtubes were found to carry little load, so they were removed, relying entirely on the combination of the steel backbone and engine for chassis rigidity. BMW's R1100 series twins of 1994 relieved the frame of stress entirely, with the engine carrying the total load from the front
Telelever BMW's motorcycle history began in 1921 when the company commenced manufacturing engines for other companies. BMW's own motorcycles—sold under the BMW Motorrad brand—began in 1923 with the BMW R 32, which was powered by a flat-twin engine (a ...
fork to the rear Monolever.


Stiffness

Frame stiffness is a problem for motorcycle designers, as it was for the
bicycle frame A bicycle frame is the main component of a bicycle, onto which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles: a main triangle ...
s that motorcycles are descendants of. Modifying the stiffness of a factory-produced frame can be undertaken to improve handling characteristics. This is often done by triangulating the factory frame. Triangulation is a technique used in many engineering applications to stiffen structures. However doing so can also have undesirable effects if it overloads other parts of the frame, as a flexible frame acts as a spring to absorb some loads.


Lateral stiffness

In the 21st century, advances like high power engines driving high traction tires, and better-performing suspension components, especially forks, led to a situation where designs with increased overall frame stiffness were made available to consumers. Analysts differ on whether infinite lateral stiffness is desirable, or whether a finite degree of built-in flex is preferable.


Motorcycle frame measurement

If the handling of the motorcycle is not appropriate, it is important to check the deformation of the geometry of the motorcycle frame. This measurement can be important after an accident or before buying a used motorcycle. There is a wide range of prices for the instruments available on the market
Touch Bike
approx. £17,00
Scheibner
Germany approx. 10,000 EUR
LaserEVO
1000 USD and finally a smar
MotoSmartLaser
250 USD available for all motorcycle service.


See also

*
Bicycle frame A bicycle frame is the main component of a bicycle, onto which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles: a main triangle ...
*
Outline of motorcycles and motorcycling The following outline is provided as an overview of motorcycles and motorcycling: Motorcycle — two-wheeled, single-track motor vehicle. Other names include: motorbike, bike, and cycle. Motorcycling — act of riding a motorcycle, around wh ...
* *
Undercarriage Undercarriage is the part of a moving vehicle that is underneath the main body of the vehicle. The term originally applied to this part of a horse-drawn carriage, and usage has since broadened to include: *The landing gear of an aircraft. *The c ...


References


Sources

* * * * * * * * * * * * {{Motorcycle components