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.
78-400: The typical motorcycle has a pair of fork tubes for the front suspension , and a swingarm with one or two shock absorbers for the rear suspension. The most common form of front suspension for a modern motorcycle is the telescopic fork . Other fork designs are girder forks, suspended on sprung parallel links (not common since the 1940s) and bottom leading link designs, not common since
156-476: A harmonic oscillator is losing energy faster than it is being supplied. A true sine wave starting at time = 0 begins at the origin (amplitude = 0). A cosine wave begins at its maximum value due to its phase difference from the sine wave. A given sinusoidal waveform may be of intermediate phase, having both sine and cosine components. The term "damped sine wave" describes all such damped waveforms, whatever their initial phase. The most common form of damping, which
234-583: A sidecar . 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 and BMW Motorcycle , while other companies (such as Douglas motorcycle ) used
312-399: A step input , the percentage overshoot (PO) is the maximum value minus the step value divided by the step value. In the case of the unit step, the overshoot is just the maximum value of the step response minus one. The percentage overshoot (PO) is related to damping ratio ( ζ ) by: Conversely, the damping ratio ( ζ ) that yields a given percentage overshoot is given by: When an object
390-701: A "fork". Examples include hub-center steering , used as early as 1920 on the Ner-a-Car , and implemented in the 1990s on the Bimota Tesi and the Yamaha GTS1000 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 -based racing motorcycle with hub-centre steering. Damping ratio In physical systems , damping
468-468: A Saxon-Motodd fork, the trail and caster angle ( 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 have reverted to conventional telescopic forks for aesthetic and packaging reasons. The Hossack/Fior fork (marketed as Duolever by BMW ) completely separates
546-408: A clean and simple appearance that bikers find attractive. Conventionally, the fork stanchions are at the top, secured by a yoke (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
624-552: A coil-over spring. In other words, the spring for the rear suspension is a coil spring that is installed over, or around, the shock. In terms of adjustment, rear shocks span the range from no adjustments whatsoever to pre-load adjustments only to racing shocks with adjustments for length, pre-load, and four different kinds of damping. Most shocks have internal oil reservoirs, but some have external ones, and some offer air-assisted damping. A number of companies offer custom-built rear shocks for motorcycles. These shocks are assembled for
702-403: 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 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
780-421: A modern sports motorcycle , 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. The Saxon-Motodd fork (marketed as Telelever by BMW ) has a wishbone that mounts to the frame and supports the monoshock unit. This relieves the forks of any braking and suspension forces. With
858-651: 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. There have been several attempts to implement front steering and suspension without using anything that could be described as
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#1732797342384936-429: A second-order system has ζ < 1 {\displaystyle \zeta <1} (that is, when the system is underdamped), it has two complex conjugate poles that each have a real part of − α {\displaystyle -\alpha } ; that is, the decay rate parameter α {\displaystyle \alpha } represents the rate of exponential decay of
1014-423: A simple damper-rod system, in which damping is controlled by the passage of fork oil through an orifice. Though cheap to manufacture, it is hard to tune such forks, as they tend to give too little damping at low slider speeds, yet too much damping at higher slider speeds. Any adjustment setting will always be a compromise, giving both over-mushy and over-stiff damping. Since forks act as hydraulic dampers, changing
1092-504: A single shock absorber rear suspension, a single shock absorber connects the rear swingarm to the motorcycle's frame. Typically this lone shock absorber is in front of the rear wheel, and uses a linkage to connect to the swing arm. Such linkages are frequently designed to give a rising rate of damping for the rear. In 1972, Yamaha introduced the Mono-Shock single shock absorber rear suspension system on their motorcycles competing in
1170-400: A specific motorcycle and rider combination, taking into account the characteristics of the motorcycle, the weight of the rider, and the rider's preferred riding style/aggressiveness. Twin shock refers to motorcycles that have two shock absorbers. Generally, this term is used to denote a particular era of motorcycles, and is most frequently used when describing off-road motorcycles. During
1248-404: A value of less than one. Critically damped systems have a damping ratio of exactly 1, or at least very close to it. The damping ratio provides a mathematical means of expressing the level of damping in a system relative to critical damping. For a damped harmonic oscillator with mass m , damping coefficient c , and spring constant k , it can be defined as the ratio of the damping coefficient in
1326-402: Is a parameter, usually denoted by ζ (Greek letter zeta), that characterizes the frequency response of a second-order ordinary differential equation . It is particularly important in the study of control theory . It is also important in the harmonic oscillator . In general, systems with higher damping ratios (one or greater) will demonstrate more of a damping effect. Underdamped systems have
1404-410: Is above the slider seal so that, if the slider seal were to leak, the oil could drain out, rendering any damping ineffective. 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 Motocycle ; it was also used by BMW for its early bikes. A leading link fork suspends the wheel on a link (or links) with a pivot point aft of
1482-412: 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 , and is available today on Harley-Davidson's Softail Springer . While it may have an exposed spring near the triple clamp, a springer fork
1560-417: Is called "total sag" or "race sag". Total sag is set to optimize the initial position of the suspension to avoid bottoming out or topping out under normal riding conditions. "Bottoming out" occurs when the suspension is compressed to the point where it mechanically cannot compress any more. Topping out occurs when the suspension extends fully and cannot mechanically extend any more. Increasing pre-load increases
1638-414: Is characterized by a swingarm that extends from the bottom of the engine/frame to the centre of the front wheel instead of a fork. The advantages of using a hub-center steering system instead of a more conventional motorcycle fork are that hub-center steering separates the steering, braking, and suspension functions. With a fork the braking forces are put through the suspension, a situation that leads to
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#17327973423841716-434: Is dissipated as heat by electric eddy currents which are induced by passing through a magnet's poles, either by a coil or aluminum plate. Eddy currents are a key component of electromagnetic induction where they set up a magnetic flux directly opposing the oscillating movement, creating a resistive force. In other words, the resistance caused by magnetic forces slows a system down. An example of this concept being applied
1794-401: Is distinguishable from a girder fork 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). The Earles fork is a variety of leading link fork where the pivot point is behind the front wheel, which is the basis of
1872-539: Is falling through the air, the only force opposing its freefall is air resistance. An object falling through water or oil would slow down at a greater rate, until eventually reaching a steady-state velocity as the drag force comes into equilibrium with the force from gravity. This is the concept of viscous drag , which for example is applied in automatic doors or anti-slam doors. Electrical systems that operate with alternating current (AC) use resistors to damp LC resonant circuits. Kinetic energy that causes oscillations
1950-415: Is important in that it provides classes used for vintage motorcycle competition. For example, vintage motocross races are held for older motocross motorcycles. To prevent the better-performing monoshock motorcycles from dominating the competition, there are separate competition classes for monoshock and twinshock motorcycles, which prevents them from competing directly against each other. On a motorcycle with
2028-438: Is intended to isolate the frame and the steering head from undesirable forces transmitted by the rear suspension by having the dampers upper mount contained within the rear swingarm subframe, rather than connecting it to the frame itself. 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
2106-482: Is not to be confused with friction , which is a type of dissipative force acting on a system. Friction can cause or be a factor of damping. The damping ratio is a dimensionless measure describing how oscillations in a system decay after a disturbance. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium . A mass suspended from a spring, for example, might, if pulled and released, bounce up and down. On each bounce,
2184-473: Is often of interest in a diverse range of disciplines that include control engineering , chemical engineering , mechanical engineering , structural engineering , and electrical engineering . The physical quantity that is oscillating varies greatly, and could be the swaying of a tall building in the wind, or the speed of an electric motor , but a normalised, or non-dimensionalised approach can be convenient in describing common aspects of behavior. Depending on
2262-598: Is the loss of energy of an oscillating system by dissipation . Damping is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. Examples of damping include viscous damping in a fluid (see viscous drag ), surface friction , radiation , resistance in electronic oscillators , and absorption and scattering of light in optical oscillators . Damping not based on energy loss can be important in other oscillating systems such as those that occur in biological systems and bikes (ex. Suspension (mechanics) ). Damping
2340-479: Is to use a reactive link or torque arm to connect the braking components to the motorcycle frame via the triple clamp. Some fork designs mitigate dive, eliminate it, or even reverse it without affecting the front suspension adversely. The Earles fork is among the latter; when braking the front brake hard, the front end of the motorcycle actually rises. BMW's Telelever fork is designed to nearly eliminate dive, and could have been designed to eliminate it completely if
2418-672: Is usually assumed, is the form found in linear systems. This form is exponential damping, in which the outer envelope of the successive peaks is an exponential decay curve. That is, when you connect the maximum point of each successive curve, the result resembles an exponential decay function. The general equation for an exponentially damped sinusoid may be represented as: y ( t ) = A e − λ t cos ( ω t − φ ) {\displaystyle y(t)=Ae^{-\lambda t}\cos(\omega t-\varphi )} where: Other important parameters include: The damping ratio
Motorcycle suspension - Misplaced Pages Continue
2496-477: The Bimota Tesi, and Vyrus motorcycles. Scott produced a motorcycle with telescopic forks in 1908, and would continue to use them on some models until 1931. In 1935 BMW became the first manufacturer to produce a motorcycle with hydraulically damped telescopic forks, although the Danish Nimbus company had un-damped telescopic forks in production in 1934. Most motorcycles today use telescopic forks for
2574-481: The Honda Valkyrie featured USD forks. Motorcycle suspensions are designed so that the springs are always under compression, even when fully extended. Pre-load is used to adjust the initial position of the suspension with the weight of the motorcycle and rider acting on it. The difference between the fully extended length of the suspension and the length compressed by the weight of the motorcycle and rider
2652-576: The Motocross World Championships . The suspension which was designed by Lucien Tilkens, became so successful that other motorcycle manufacturers developed their own single shock absorber designs. Honda 's version is called Pro-link , Kawasaki 's is Uni-Trak , and Suzuki 's is Full-Floater . Honda's Unit Pro-Link , used first on the Honda RC211V MotoGP racer, and then on the 2003 Honda CBR600RR sport bike,
2730-758: The 1909 A.S.L. which had both front and rear pneumatic suspension, the 1913 Indian Single with a swingarm suspended from a leaf spring and the 1913 Pope with wheels supported on a pair of plungers which were each suspended by a coil spring . Several motorcycles before and immediately after World War II used plunger suspension in which the vertical movement of the rear axle was controlled by plungers suspended by springs. Notable manufacturers of motorcycles with plunger suspension include Adler , Ariel , BMW , BSA , Indian , MZ , Saroléa , Norton , Cossack/Ural and Zündapp . Although plunger suspension could be sophisticated, with springing and damping in both compression and rebound, it had three disadvantages (compared to
2808-492: The 1960s. Some manufacturers (e.g. Greeves) used a version of the swinging arm for front suspension on their motocross designs. A single-sided version of the idea is also used in motor scooters such as the Vespa . The hub-center steering as developed by Ascanio Rodorigo , on a concept associated to Massimo Tamburini is a complex front swingarm alternative system that entails suspension and steering, as seen in projects such as
2886-570: The Earles design on their roadsters or off-road machines. BMW used Earles forks on all their motorcycles between 1955 and 1968. 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 from 1948. Girdraulic forks featured hydraulic damping with forged alloy blades providing extra strength. While both may have an exposed spring near
2964-445: The Earles' patent. Patented by Englishman 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
3042-409: The almost universal swingarm that succeeded it), as follows: (i) wheel travel was limited, (ii) the wheel could move out of the required vertical axis, and (iii) it was more expensive to produce and maintain. The basic motorcycle swingarm is a quadrilateral, with one short side connected to the motorcycle's frame with bearings so that it can pivot. The other short side is the rear axle around which
3120-417: The amount of damping present, a system exhibits different oscillatory behaviors and speeds. A damped sine wave or damped sinusoid is a sinusoidal function whose amplitude approaches zero as time increases. It corresponds to the underdamped case of damped second-order systems, or underdamped second-order differential equations. Damped sine waves are commonly seen in science and engineering , wherever
3198-410: The damping function. The emulator has a very small orifice for low fork-speed damping, and an adjustable shim-stack for high fork-speed damping. Gas-charged cartridge forks , which became available in 2007, consist of gas-charged cartridges fitted within standard forks. This kit is suitable for supersport classes of racing, where regulations prohibit a complete fork replacement but allow modification of
Motorcycle suspension - Misplaced Pages Continue
3276-584: The definition of the damping ratio above, we can rewrite this as: This equation is more general than just the mass–spring system, and also applies to electrical circuits and to other domains. It can be solved with the approach where C and s are both complex constants, with s satisfying Two such solutions, for the two values of s satisfying the equation, can be combined to make the general real solutions, with oscillatory and decaying properties in several regimes: The Q factor , damping ratio ζ , and exponential decay rate α are related such that When
3354-462: The effectiveness of the suspension. The length of the typical motorcycle fork means that they act as large levers about the headstock requiring the forks, the headstock, and the frame to be very robust adding to the bike's weight. The endurance racer "Nessie", built by the Mead & Tomkinson racing team, used an adapted version of Difazio hub-center steering , whereby braking forces were directed to
3432-422: The end of this period, most of these motorcycles had rear wheel travel of approximately 12 inch (30 cm). At the beginning of this period, various rear suspension designs were used to reach this degree of performance. However, by the end of this period, a design consisting of using only one shock absorber (instead of two) was universally accepted and used. The performance of single shock absorber suspensions
3510-477: The fork oil. This valve has a number of such shims of varying thicknesses that cover the orifices in the valve to control the damping of the fork on high and medium speed bumps. Some of the shims (or "leaf springs") lift with little force allowing fluid to flow through the orifice. Other springs require greater force to lift and allow flow. This gives the fork digressive damping, allowing it to be stiff over small bumps, yet relatively softer over larger bumps. Also,
3588-699: The forks to be turned in order to steer the motorcycle. The bottom of the forks carries the front wheel's axle. On conventional telescopic forks, the lower portion or fork bodies ( "fork sliders" in the UK), slide up and down the fork tubes ( "fork stanchions" in the UK). The fork tubes must be mirror-smooth to seal the fork oil inside the fork. Some fork tubes, especially on early roadsters and off-road motorcycles, are enclosed in concertina plastic/rubber protective "gaiters". "Upside-down" (USD) forks , also known as inverted forks, are installed inverted compared with conventional telescopic forks. The slider bodies are at
3666-415: The frame via a pivoted fork (rather than through the steering head ). This allowed neutral steering and an absence of brake dive. While front suspensions were almost universally adopted before World War I, several manufacturers did not use rear suspension on their bikes until after World War II. However, motorcycles with rear suspension were offered to the public before World War I. Notable among these are
3744-401: The front end will feel stiffer, in the 1980s various manufacturers attempted to get round this by methods of anti-dive such as: With the advent of cartridge forks, which allow more low speed damping and less high speed damping than the previous damping rod forks, separate anti-dive mechanisms have generally fallen out of use. Another method to reduce or eliminate brake dive in telescopic forks
3822-409: The front forks, it can also cause handling and braking problems. One of the purposes of a suspension is to help maintain contact between the tire and road. If the suspension has bottomed out, it is no longer moving as it should, and is no longer helping to maintain contact. While excessive brake dive is disconcerting, and bottoming out can cause loss of traction, a certain amount of brake dive reduces
3900-405: The front suspension. The forks can most easily be understood as simply encased long coil springs with hydraulic damping of excess spring energy. They allow the front wheel to react to imperfections in the road while isolating the rest of the motorcycle from that motion. The top of the forks are connected to the motorcycle's frame in a triple tree clamp (known as a "yoke" in the UK), which allows
3978-429: The front wheel is transmitted through the forks, which compress. This shortening of the forks causes the front end of the bike to move lower, and this is called brake dive . Telescopic forks are particularly prone to this, unlike leading link designs. Brake dive can be disconcerting to the rider, who may feel like he or she is about to be thrown over the front of the motorcycle. If the bike dives so far as to bottom out
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#17327973423844056-407: The initial force on the spring thereby reducing total sag. Decreasing pre-load decreases the initial force in the spring thereby increasing total sag. Some motorcycles allow adjustment of pre-load by changing the air pressure inside the forks. Valves at the top of the forks allow air to be added or released from the fork. More air pressure gives more pre-load, and vice versa. Basic fork designs use
4134-420: The late 1970s and 1980s, motorcycle rear suspension design and performance underwent tremendous advances. The primary goal and result of these advances were increased rear wheel travel, as measured in how far the rear wheel could move up and down. Before this period of intense focus on rear suspension performance, most off-road motorcycles had rear wheel travel of about 3.5–4 inch (9–10 cm). At
4212-479: The manufacturer chose to do so. Leading link front forks, such as used on some Ural motorcycles , can also be designed either to reduce or eliminate dive. The Saxon-Motodd (marketed as Telelever by BMW ) has an additional swingarm that mounts to the frame and supports the spring. This causes the rake and trail to increase during braking instead of decreasing as with traditional telescopic forks. The Hossack/Fior (marketed as Duolever by BMW ) separates completely
4290-456: The original forks. Applying the brakes of a moving motorcycle increases the load borne by the front wheel and decrease the load borne by the rear wheel due to a phenomenon called load transfer . For a detailed explanation and a sample calculation, see the braking section of the Bicycle and motorcycle dynamics article. If the motorcycle is equipped with telescopic forks , the added load on
4368-650: The oscillations. A lower damping ratio implies a lower decay rate, and so very underdamped systems oscillate for long times. For example, a high quality tuning fork , which has a very low damping ratio, has an oscillation that lasts a long time, decaying very slowly after being struck by a hammer. For underdamped vibrations, the damping ratio is also related to the logarithmic decrement δ {\displaystyle \delta } . The damping ratio can be found for any two peaks, even if they are not adjacent. For adjacent peaks: where x 0 and x 1 are amplitudes of any two successive peaks. As shown in
4446-407: The rake and trail of the motorcycle, allowing it to turn more easily. This is especially important to racers trail braking on entrance to corners. Brake dive with telescopic forks can be reduced by either increasing the spring rate of the fork springs, or increasing the compression damping of the forks. However, all of these changes make the motorcycle less pleasant to ride on rough roads, since
4524-480: The rear axle can usually be adjusted forward and back in relation to the swingarm, to adjust chain tension, but a few models (such as some 1971/72 Triumph and BSA four-strokes and Ducati 860 GTS and Darmah 900s ) make the adjustment at the swingarm's pivot point. The hydraulic shock absorbers used on the rear suspensions of motorcycles are essentially the same as those used in other vehicle applications. Motorcycle shocks do differ slightly in that they nearly always use
4602-422: The rear wheel turns. The long sides are connected to the motorcycle's frame or rear sub-frame with one or two shocks with coil-over springs. In production motorcycles, swingarms are not exactly rectangular, but their function can be more easily understood by thinking of them as such. When a swingarm is present on only one side of the motorcycle, this is known as a single-sided swingarm . In 1981 BMW introduced
4680-482: The right figure: where x 1 {\displaystyle x_{1}} , x 3 {\displaystyle x_{3}} are amplitudes of two successive positive peaks and x 2 {\displaystyle x_{2}} , x 4 {\displaystyle x_{4}} are amplitudes of two successive negative peaks. In control theory , overshoot refers to an output exceeding its final, steady-state value. For
4758-579: The setup. Notable exclusions are the Ducati 916 which was intended to be taken endurance racing, the MV Agusta f4 which has a hollow interior for reduced weight (a magnesium version is also available), and the Ducati 1098, which was given a single sided swingarm purely for styling reasons. On many shaft-drive motorcycles the drive shaft is contained in one of the long sides of the swingarm. Notable examples include all post-1955 BMW models prior to BMW's use of
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#17327973423844836-577: The single sided swingarm (mono lever) to motorcycles on their R 80 GS model. Notable examples include the Honda VFR800 and the BMW R- and K-series. Single-sided swingarms make rear-wheel removal easier, though they generally increase the unsprung weight of the rear suspension. This is due to the additional material required to give identical torsional rigidity to a conventional (two-sided) swingarm setup. For this reason sports bikes are rarely seen using
4914-765: The single-sided swingarms, Urals , many Moto Guzzi twins, the Honda Goldwing , the Yamaha XS Eleven , and the Yamaha FJR1300 . The BMW R- and K-series combine a shaft-drive contained in the swing arm with a single-sided swingarm, and the combination is marketed as the Paralever . Newer Moto Guzzi motorcycles use a similar arrangement marketed as the CA.R.C. ("CArdano Reattivo Compatto" - Compact Reactive Shaft Drive). For motorcycles with chain drives,
4992-430: The springs (or shims) only allow flow in one direction, so one set of springs controls compression damping, and another rebound damping. This allows the dampings to be set separately. Cartridge emulators are aftermarket parts that make damper-rod forks behave virtually as cartridge forks. The damping orifice in the damper-rod is made so large that it has virtually no effect on damping, and instead an "emulator" takes over
5070-399: The suspension being compressed, using up a large amount of suspension travel which makes dealing with bumps and other road irregularities extremely difficult. As the forks dive the steering geometry of the bike also changes making the bike more nervous, and inversely on acceleration becomes more lazy. Also, having the steering working through the forks causes problems with stiction , decreasing
5148-462: 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 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
5226-667: The suspension from steering forces. Developed by Norman Hossack and used by Claude Fior and John Britten 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 , K1200S , K1300S , K1200GT and K1300GT . Developed by MotoCzysz for their C1 and awarded United States Patent 7111700 on September 26, 2006. Defined as
5304-534: The suspension from steering forces. It was developed by Norman Hossack though used by Claude Fior and John Britten on racebikes. Hossack himself described the system as a 'steered upright'. In 2004 BMW announced the K1200S with a new front suspension that is based upon this design. A single-sided front swingarm suspension was used on the Yamaha GTS1000 , introduced in 1993. The GTS used the RADD, Inc. front suspension designed by James Parker. A single sided girder fork
5382-576: The system tends to return to its equilibrium position, but overshoots it. Sometimes losses (e.g. frictional) damp the system and can cause the oscillations to gradually decay in amplitude towards zero or attenuate . The damping ratio is a measure describing how rapidly the oscillations decay from one bounce to the next. The damping ratio is a system parameter, denoted by ζ (" zeta "), that can vary from undamped ( ζ = 0 ), underdamped ( ζ < 1 ) through critically damped ( ζ = 1 ) to overdamped ( ζ > 1 ). The behaviour of oscillating systems
5460-470: The system's differential equation to the critical damping coefficient: where the system's equation of motion is and the corresponding critical damping coefficient is or where The damping ratio is dimensionless, being the ratio of two coefficients of identical units. Using the natural frequency of a harmonic oscillator ω n = k / m {\textstyle \omega _{n}={\sqrt {{k}/{m}}}} and
5538-512: The top, fixed in the triple clamps , and the stanchion tubes are at the bottom, fixed to the axle . This USD arrangement has two advantages: (i) it decreases the unsprung weight of the motorcycle; and (ii) it increases torsional stiffness , which can improve handling. Two disadvantages of USD forks are: (i) they are more expensive than conventional telescopic forks; and (ii) they are liable to lose all their damping oil should an oil seal fail. USD forks are typically found on sportbikes , though
5616-477: The triple clamp, a girder fork is distinguishable from a springer fork 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 ,
5694-752: The upper triple clamp. The fork and its attachment points on the frame establish the critical geometric parameters of rake and trail , 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 . A variety of fork arrangements have been tried during more than one hundred years of motorcycle development, several of which remain available today. A telescopic fork uses fork tubes which contain
5772-410: The weight of the fork oil will alter the damping rate. Some telescopic forks have external adjustments for damping. A more sophisticated approach is the cartridge fork , which use internal cartridges with a valving system. Damping at low slider speeds is controlled by a much smaller orifice, but damping at higher slider speeds is controlled by a system of flexible shims, which act as a bypass valve for
5850-480: The wheel axle. Russian Ural motorcycles used leading link forks on sidecar 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 , 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 springer fork
5928-429: 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
6006-652: Was use on the German Imme R100 motorcycle between 1949 and 1951, and the Vespa scooter has a single-sided trailing-link fork . More recently, between 1998 and 2003, the ItalJet " Dragster " scooter also used a single-sided swingarm suspension, though unlike the GTS1000 there was no upper control arm; the upper part of the suspension on the Dragster served only to transmit steering input. Hub-center steering
6084-508: Was vastly superior to twin shock motorcycles. Accordingly, this design distinction is readily used to categorize motorcycles. With the exception of Bentley and Draper system ( New Imperial and Brough Superior machines) and the HRD (later Vincent ) system both developed and patented in the 1920s it is only since the 1980s that monoshock motorcycles have been the norm, the term "twinshock" is now used to categorize vintage motorcycles. This distinction
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