![Honda-rune](https://upload.wikimedia.org/wikipedia/commons/8/8c/Honda-rune.jpg)
A motorcycle fork connects a
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
's front wheel and axle to its
frame
A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent.
Frame and FRAME may also refer to:
Physical objects
In building construction
*Framing (con ...
, typically via a yoke, also known as a triple clamp, which consists of an upper yoke joined to a lower yoke via a steering stem, a shaft that runs through the steering head, creating the steering axis. Most forks incorporate the front
suspension
Suspension or suspended may refer to:
Science and engineering
* Suspension (topology), in mathematics
* Suspension (dynamical systems), in mathematics
* Suspension of a ring, in mathematics
* Suspension (chemistry), small solid particles suspend ...
and front brake, and allow the front wheel to rotate about the steering axis so that the bike may be steered. Most
handlebars attach to the top clamp in various ways, while clip-on handlebars clamp to the fork tubes, either just above or just below the upper triple clamp.
The fork and its attachment points on the frame establish the critical geometric parameters of
rake and trail
Bicycle and motorcycle geometry is the collection of key measurements (lengths and angles) that define a particular bike configuration. Primary among these are wheelbase, steering axis angle, fork offset, and trail. These parameters have a major ...
, which play a major role in defining how a motorcycle handles and
dives during braking.
While the standard telescopic fork arrangement is found with few major differences among mainstream street motorcycles since the 1970s, historically there have been many variations, including trailing or leading link, springer, Earles, girder, and others, as well as non-fork steering such as
hub-center steering
Hub-center steering (HCS) is one of several different types of front-end suspension/steering mechanisms used in motorcycles and cargo bicycles. Hub-center steering is characterized by the steering pivot points being inside the hub of the wheel, ra ...
.
Variations
A variety of fork arrangements have been tried during more than one hundred years of motorcycle development, several of which remain available today.
Telescopic
![R12-fork](https://upload.wikimedia.org/wikipedia/commons/c/ca/R12-fork.jpg)
A
telescopic fork
A telescopic fork is a form of motorcycle front suspension whose use is so common that it is virtually universal. The telescopic fork uses fork tubes and sliders which contain the springs and dampers.
The main advantages of the telescopic fork ...
uses
fork tube
A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a yoke, also known as a triple clamp, which consists of an upper yoke joined to a lower yoke via a steering stem, a shaft that runs through the steering ...
s which contain the suspension components (coil springs and damper) internally. This is the most common form of fork commercially available. It may or may not include
gaiters
Gaiters are garments worn over the shoe and bottom of the pant or trouser leg, and used primarily as personal protective equipment; similar garments used primarily for display are spats.
Originally, gaiters were made of leather or canvas. T ...
for protection against abrasive elements on the suspension cylinders. The main advantages of the telescopic fork are that (i) it is simple in design and relatively cheap to manufacture and assemble; (ii) it is lighter than older designs using external components and linkage systems; and (iii) it has a clean and simple appearance that bikers find attractive.
Conventionally, the fork
stanchions are at the top, secured by a
yoke
A yoke is a wooden beam sometimes used between a pair of oxen or other animals to enable them to pull together on a load when working in pairs, as oxen usually do; some yokes are fitted to individual animals. There are several types of yoke, us ...
(also called a triple tree or a triple clamp), and the sliders are at the bottom, attached to the front wheel spindle. On some modern sport bikes and most off-road bikes, this system is inverted, with "sliders" (complete with the spring/damper unit) at the top, clamped to the yoke, while the stanchions are at the bottom. This is done (i) to reduce unsprung weight by having the heavier components suspended, and (ii) to improve the strength and rigidity of the assembly by having the strong large-diameter "sliders" clamped in the yokes.
The inverted system is referred to as an ''upside-down fork'', or "USD" for short. A disadvantage of this USD design is that the entire reservoir of damping oil is above the slider seal so that, if the slider seal were to leak, the oil could drain out, rendering any damping ineffective.
Trailing link
![Indian Big Chief fork](https://upload.wikimedia.org/wikipedia/commons/1/1d/Indian_Big_Chief_fork.PNG)
A trailing link fork suspends the wheel on a link (or links) with a pivot point forward of the wheel axle. Most famously used by
Indian ; it was also used by BMW for its early bikes.
Leading link
![Ural-fork](https://upload.wikimedia.org/wikipedia/commons/5/5f/Ural-fork.jpg)
A leading link fork suspends the wheel on a link (or links) with a pivot point aft of the wheel axle. Russian
Ural
Ural may refer to:
*Ural (region), in Russia and Kazakhstan
*Ural Mountains, in Russia and Kazakhstan
*Ural (river), in Russia and Kazakhstan
* Ual (tool), a mortar tool used by the Bodo people of India
*Ural Federal District, in Russia
*Ural econ ...
motorcycles used leading link forks on
sidecar
A sidecar is a one-wheeled device attached to the side of a motorcycle, scooter, or bicycle, making the whole a three-wheeled vehicle. A motorcycle with a sidecar is sometimes called a ''combination'', an ''outfit'', a ''rig'' or a ''hack''.
...
equipped motorcycles, and aftermarket leading link forks are often installed today on motorcycles when they are outfitted with sidecars. They are also very popular with
trikes
Trike may refer to:
Vehicles with three wheels and seated
* Drift trike, a type of recreational tricycle with no pedals
* Electric trike
* Motorized tricycle
* Three-wheeler
* Tricycle (non-motorized)
* Ultralight trike, a type of powered hang ...
, improving the handling while steering or braking. The most common example of a leading link fork is that found on the
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, a ...
.
Springer
![Harley-Davidson 9](https://upload.wikimedia.org/wikipedia/commons/3/35/Harley-Davidson_9.jpg)
The springer fork is an early type of leading link fork. A springer fork does not have the suspension built into the fork tubes, but instead has it mounted externally, where it may be integrated into the triple clamp. This style of fork may be found on antique motorcycles or
choppers
Chopper may refer to:
Arts and entertainment
* Chopper (comics), ''Chopper'' (comics), a horror comic book mini-series
* Chopper (film), ''Chopper'' (film), a 2000 Australian film by and about Mark "Chopper" Read
* Chopper (Judge Dredd), Chopper ...
, and is available today on
Harley-Davidson's ''Softail Springer''.
While it may have an exposed spring near the triple clamp, a springer fork is distinguishable from a
girder fork
A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a yoke, also known as a triple clamp, which consists of an upper yoke joined to a lower yoke via a steering stem, a shaft that runs through the steering ...
by its two parallel sets of legs. The rear is firmly fixed to the bottom triple clamp (usually brazed or welded). A short leading link holds the wheel and the forward leg which actuates the springs (usually mounted on the triple clamp).
Earles
![Douglas-fork-1952](https://upload.wikimedia.org/wikipedia/commons/d/d5/Douglas-fork-1952.jpg)
The Earles fork is a variety of leading link fork where the pivot point is behind the front wheel, which is the basis of the Earles' patent.
Patented by
Englishman
The English people are an ethnic group and nation native to England, who speak the English language, a West Germanic language, and share a common history and culture. The English identity is of Anglo-Saxon origin, when they were known in ...
Ernest Earles in 1953, the design is constructed of light tubing, with conventional 'shock absorbers' mounted near the front axle. The Earles fork has a very small wheelbase change under braking or under compression, unlike telescopic forks. Their construction is much stronger than teleforks, especially against lateral deflection caused by hard cornering (as when racing), or when cornering with a
sidecar
A sidecar is a one-wheeled device attached to the side of a motorcycle, scooter, or bicycle, making the whole a three-wheeled vehicle. A motorcycle with a sidecar is sometimes called a ''combination'', an ''outfit'', a ''rig'' or a ''hack''.
...
.
This triangulated fork causes the front end of a motorcycle to rise slightly when braking hard, as the mechanical braking forces rotate 'downward' relative to the fork's pivot point. This action can be disconcerting to riders used to telescopic forks, which have the opposite reaction to braking forces ('brake dive'). Several motorcycle manufacturers licensed the Earles patent forks for racing motorcycles in 1953, such as
MV Agusta
MV Agusta (, full name: MV AGUSTA Motor S.p.A., original name: Meccanica Verghera Agusta or MV) is a motorcycle manufacturer founded by Count Domenico Agusta on 19 January 1945 as one of the branches of the Agusta aircraft company near Milan in ...
and
BMW Motorcycle
BMW Motorrad is the motorcycle brand of BMW, part of its Corporate and Brand Development division. It has produced motorcycles since 1923, and achieved record sales for the fifth year in succession in 2015. With a total of 136,963 vehicles sold in ...
, while other companies (such as
Douglas motorcycle) used the Earles design on their roadsters or off-road machines. BMW used Earles forks on all their motorcycles between 1955 and 1968.
Girder
![Cotton-fork](https://upload.wikimedia.org/wikipedia/commons/b/b7/Cotton-fork.jpg)
One of the earliest types of motorcycle front suspension, the girder fork consists of a pair of uprights attached to the triple clamp by linkages with a spring usually between the top and bottom triple clamps. The design reached a peak in the "Girdraulics" used on
Vincent motorcycles
Vincent Motorcycles was a British manufacturer of motorcycles from 1928 to 1955. The business was established by Philip Vincent who bought an existing manufacturing name HRD, initially renaming it as ''Vincent HRD'', producing his own motorcy ...
from 1948. Girdraulic forks featured hydraulic damping with forged alloy blades providing extra strength.
While both may have an exposed spring near the triple clamp, a girder fork is distinguishable from a
springer fork
A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a yoke, also known as a triple clamp, which consists of an upper yoke joined to a lower yoke via a steering stem, a shaft that runs through the steering h ...
by the wheel being fixed firmly to the (usually a long diamond shape) upright. The pivot points are short links mounted to the top and bottom triple clamps. The spring is usually mounted to the girder and compressed against the upper triple clamp.
Although girder forks are associated with early motorcycles, the British
Ariel Ace
The Ariel Ace is a 2014 sports motorcycle that is manufactured by the British Ariel Motor Company in Crewkerne, Somerset, England. It uses the V4 engine from the Honda VFR1200.
It is the Ariel marque's first new motorcycle in more than 50 ye ...
, a modern
sports
Sport pertains to any form of competitive physical activity or game that aims to use, maintain, or improve physical ability and skills while providing enjoyment to participants and, in some cases, entertainment to spectators. Sports can, th ...
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
, has an alloy space frame and a matching girder fork. This Ariel girder fork is just as prone to brake dive as any telescopic fork, but is claimed to be more resistant to torsional twisting.
Saxon-Motodd (Telelever)
![BMW R1150R no logo](https://upload.wikimedia.org/wikipedia/commons/3/36/BMW_R1150R_no_logo.jpg)
The Saxon-Motodd fork (marketed as Telelever by
BMW) has a wishbone that mounts to the frame and supports the
monoshock
A motorcycle's suspension serves a dual purpose: contributing to the vehicle's handling and braking, and providing safety and comfort by keeping the vehicle's passengers comfortably isolated from road noise, bumps and vibrations.
The typical moto ...
unit. This relieves the forks of any braking and suspension forces. With a Saxon-Motodd fork, the trail and
caster angle
250px, θ is the caster angle, the red line is the pivot line, and the grey area is the tire.
250px, Front suspension of a race car, the caster angle is formed by the line between upper and lower ball joint.
The caster angle or castor angle is t ...
(
rake) increases during braking instead of decreasing as with traditional telescopic forks.
BMW's boxer twins have been equipped with Telelever forks since 1994, but some newer boxers like the
BMW R nineT
The BMW R nineT is a standard motorcycle made by BMW Motorrad since 2014. It is a retro styled roadster marketed by BMW to custom builders and enthusiasts as a "blank canvas for customizing".
All models have anti-lock braking systems (ABS). Aut ...
have reverted to conventional telescopic forks for aesthetic and packaging reasons.
Hossack/Fior (Duolever)
![Duolever600](https://upload.wikimedia.org/wikipedia/commons/e/eb/Duolever600.jpg)
The Hossack/Fior fork (marketed as Duolever by
BMW) completely separates the suspension from steering forces. Developed by
Norman Hossack
Norman Hugh Hossack is a Scottish inventor and engineer, who invented the Hossack motorcycle front suspension system, used on some BMW Motorrad K series motorcycles.
Early life
Norman Hossack was born in Bellshill, Scotland, and grew up in ...
and used by Claude Fior and
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 ...
on racebikes, Hossack described the system as a 'steered upright'. In 2004 BMW announced the K1200S with a new front suspension that appears to be based upon the design. As of 2006, the Duolever is on the BMW K models:
K1200R,
K1300R
The BMW K1300R is a naked motorcycle made by BMW from 2008 to 2015. When launched, it replaced the K1200R as BMW's flagship urban motorcycle. BMW says the K1300R produces @ 9,250 rpm and torque @ 8,250 rpm from its inline-four engi ...
,
K1200S
K1, K.I, K01, K 1 or K-1 can mean:
Geography
* K1, another name for Masherbrum, a mountain in the Karakoram range in Pakistan
* K1, a small town to north of Kirkuk city, Iraq
* K1 (building), a high-rise building in Kraków, Poland
Mathematics ...
,
K1300S K13 or K-13 may refer to:
* ''K-13'' (film), a 2019 Indian Tamil psychological mystery thriller
* K-13 (Kansas highway)
* K-13 (missile), a Soviet air-to-air missile
* K13 gas fields, in the North Sea
* , a submarine of the Royal Navy
* Keratin 1 ...
,
K1200GT
K1, K.I, K01, K 1 or K-1 can mean:
Geography
* K1, another name for Masherbrum, a mountain in the Karakoram range in Pakistan
* K1, a small town to north of Kirkuk city, Iraq
* K1 (building), a high-rise building in Kraków, Poland
Mathematics
...
and
K1300GT K13 or K-13 may refer to:
* ''K-13'' (film), a 2019 Indian Tamil psychological mystery thriller
* K-13 (Kansas highway)
* K-13 (missile), a Soviet air-to-air missile
* K13 gas fields, in the North Sea
* , a submarine of the Royal Navy
* Keratin 13
...
.
Coaxial steering front suspension
Developed by
MotoCzysz
MotoCzysz (pronounced ) was an American motorcycle company based in Portland, Oregon that intended to compete in MotoGP. The C1 prototype engine was designed with perfect balance not needing a balance shaft. Some of the patented innovations inclu ...
for their C1 and awarded United States Patent 7111700 on September 26, 2006.
Defined as a motorcycle or bicycle front end having coaxial steering and suspension components, and having telescopic forks. Swing weight of the forks is dramatically reduced by removing their suspension components to the central location, coaxially within the steering tube. Ride height can be adjusted without loosening the forks in the triple clamps.
This particular fork, as implemented on the MotoCzysz C1, also has adjustable trail, from 89 mm to 101 mm.
Non-forks
![Omega shaped chassis](https://upload.wikimedia.org/wikipedia/commons/6/68/Omega_shaped_chassis.jpg)
There have been several attempts to implement front steering and suspension without using anything that could be described as a "fork". Examples include
hub-center steering
Hub-center steering (HCS) is one of several different types of front-end suspension/steering mechanisms used in motorcycles and cargo bicycles. Hub-center steering is characterized by the steering pivot points being inside the hub of the wheel, ra ...
, used as early as 1920 on the
Ner-a-Car,
and implemented in the 1990s on the
Bimota
Bimota is an Italian manufacturer of custom and production motorcycles. It was founded in 1973 in Rimini by Valerio Bianchi, Giuseppe Morri, and Massimo Tamburini. The company name is a portmanteau derived from the first two letters of each of th ...
Tesi
and the
Yamaha GTS1000
The Yamaha GTS1000 is a sport-touring motorcycle introduced by Yamaha in 1993, sold until 1994 in the United States, and sold elsewhere until 1999. It is notable for its forkless front suspension, specifically a RADD, Inc., front suspension desi ...
A single-sided girder "fork" was used by the German firm
Imme between 1949 and 1951.
Mead & Tomkinson Racing competed in endurance racing in the 1970s with "Nessie," a
Laverda
Laverda (''Moto Laverda S.A.S. – Dottore Francesco Laverda e fratelli'') was an Italian manufacturer of high performance motorcycles. The motorcycles in their day gained a reputation for being robust and innovative.
The Laverda brand was abso ...
-based racing motorcycle with hub-centre steering.
See also
*
Bicycle and motorcycle dynamics
Bicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics falls under a branch of physics known as classical mechanics. Bike motions of interest in ...
*
Bicycle and motorcycle geometry
Bicycle and motorcycle geometry is the collection of key measurements (lengths and angles) that define a particular bike configuration. Primary among these are wheelbase, steering axis angle, fork offset, and trail. These parameters have a major ...
*
Bicycle fork
A bicycle fork is the part of a bicycle that holds the front wheel.
A fork typically consists of two ''blades'' which are joined at the top by a fork ''crown.'' The crown is often at the front. Most suspension forks have an arch connecting the ...
*
Hub-center steering
Hub-center steering (HCS) is one of several different types of front-end suspension/steering mechanisms used in motorcycles and cargo bicycles. Hub-center steering is characterized by the steering pivot points being inside the hub of the wheel, ra ...
*
Suspension (motorcycle)
A motorcycle's suspension serves a dual purpose: contributing to the vehicle's handling and braking, and providing safety and comfort by keeping the vehicle's passengers comfortably isolated from road noise, bumps and vibrations.
The typical moto ...
*
Suspension (mechanics)
References
{{DEFAULTSORT:Motorcycle Fork
Fork
In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods ei ...
Fork
In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods ei ...