| The most common form of front suspension for a | | | | the tire and road. If the suspension has bottomed |
| motorcycle is the telescopic fork. Early front | | | | out, it is no longer moving as it should, and no longer |
| suspension designs used frames with springs. | | | | longer helping to maintain contact. |
| Some British manufacturers (eg Greeves) used a | | | | Brake dive can be reduced by: |
| version of the swinging arm for front suspension on | | | | Increasing the spring rate of the fork springs |
| their motocross designs. A single-sided version of the | | | | Increasing the pre-load |
| idea was also used in motor scooters such as the | | | | Increasing the compression damping of the forks |
| Vespa | | | | However, all of these changes make make the |
| Telescopic forks | | | | motorcycle less pleasant to ride on rough roads, since |
| In 1935 BMW was the first manufacturer to produce | | | | the front end will feel stiffer. |
| a motorcycle, the R12, with hydraulically damped | | | | Telelever |
| telescopic forks. Most motorcycles today use | | | | BMW introduced its Telelever Front Suspension in |
| telescopic forks for the front suspension. The forks | | | | 1993. The Telelever uses a linkage and single hydraulic |
| can be most easily understood as simply large | | | | shock with external spring to replace the more |
| hydraulic shock absorbers with internal coil springs. | | | | common telescopic front fork suspension. |
| They allow the front wheel to react to imperfections | | | | The Telelever, according to BMW, "separates |
| in the road while isolating the rest of the motorcycle | | | | suspension and steering." It is most commonly praised |
| from that motion. | | | | for virtually eliminating braking dive. It is standard on |
| The top of the forks are connect to the | | | | BMW's R-series motorcycles and was standard on all |
| motorcycle's frame in a triple tree clamp (otherwise | | | | the K-series bikes until the introduction of the |
| known to British riders as the top yoke and bottom | | | | K1200S. |
| yoke), which allows the forks to be turned in order | | | | BMW introduced a copy of a front suspension |
| to steer the motorcycle. | | | | system designed by Norman Hossakfor the K1200S, |
| The bottom of the forks are connected to the front | | | | naming it Duolever. |
| axle around which the front wheel turns. The front | | | | Single-sided |
| brakes are also connected to the forks, and act | | | | The only production motorcycle to use a single-sided |
| against a rotor or drum attached to the front wheel. | | | | front swingarm suspension was Yamaha's GTS1000, |
| On typical forks, the upper portion, known as the | | | | introduced in 1993. The GTS used the RADD front |
| fork tubes, slide inside the fork bodies, which are the | | | | suspension designed by James Parker. |
| lower part of the forks. As the tubes slide in and out | | | | Rear suspension |
| of the body they are telescoping, thus the term | | | | Swingarms |
| telescopic forks. The fork tubes must be smooth to | | | | The basic motorcycle swingarm is a rectangle, with |
| seal the fork oil inside the fork, and typically have a | | | | one short side connected to the motorcycle's frame |
| mirrored finish, though some fork tubes, especially | | | | with bearings so that it can pivot. The other short |
| those on off-road motorcycles, are enclosed in plastic | | | | side is the rear axle around which the rear wheel |
| protective sleeves, known as gaiters. | | | | turns. The long sides are connected to the |
| "Upside-down" (USD) forks are installed inverted | | | | motorcycle's frame or rear sub-frame with one or |
| compared to typical forks, with the tubes at the | | | | two shocks with coil-over springs. |
| bottom and the bodies at the top. This decreases | | | | In production motorcycles, swingarms are not exactly |
| the unsprung weight of the motorcycle and improves | | | | rectangular, but their function can be more easily |
| its handling. USD forks are usually found on | | | | understood by thinking of them as such. |
| sportbikes, though Honda's large power-cruiser, the | | | | Some swing arms have only one long-side, and are |
| Valkyrie, sported USD forks. | | | | know as single-sided swingarms. Notable examples |
| Pre-load adjustment | | | | include the Honda VFR800 and the BMW R- and |
| When a motorcycle's forks are compressed or | | | | K-series of motorcycles. Single-sided swingarms make |
| extended, the fork springs inside them are under | | | | rear-wheel removal easier and reduce the unsprung |
| compression or tension, respectively. | | | | weight of the rear suspension. |
| Pre-load is an amount of additional compression force | | | | On many shaft-drive motorcycles the drive shaft is |
| the springs experience when the forks are at a given | | | | contained in one of the long sides of the swingarm. |
| position. When you adjust the pre-load, you are | | | | Notable examples include the Honda Goldwing and the |
| either increasing or decreasing the amount of that | | | | Yamaha FJR1300. |
| force. | | | | The BMW R- and K-series combine a shaft-drive |
| When you increase the pre-load, you increase the | | | | contained in the swing arm with a single-sided |
| additional force at any given position of the forks | | | | swingarm, and the combination is marketed as the |
| under compression. This causes the forks to extend | | | | Paralever. Newer Moto Guzzi motorcycles use a |
| more under any given external force than they | | | | similar arrangement marketed as the CA.R.C. |
| would at a lower pre-load setting. Therefore, the | | | | ("CArdano Reattivo Compatto" - Compact Reactive |
| forks have to experience greater external force | | | | Shaft Drive). |
| before they bottom out, or reach the maximum | | | | For motorcycles with chain drives, the rear axle can |
| compression travel. The pre-load can be used for | | | | be adjusted forward and back in relation to the |
| suspension tuning (see below). | | | | swingarm, to adjust chain tension. |
| Some motorcycles have externally accessible pre-load | | | | Shock absorbers |
| adjustments. Typically, this is a screw-type | | | | The hydraulic shock absorbers used on the rear |
| adjustment that moves a backing plate inside the | | | | suspensions of motorcycles are essentially the same |
| fork against the top of the fork spring. The farther | | | | as those used in other vehicle applications. For more |
| down the adjuster is screwed, the more force is | | | | detail, see the article on shock absorbers. |
| applied to the spring, and the higher the preload. | | | | Motorcycle shocks do differ slightly in that they |
| A few motorcycles allow adjustment of pre-load by | | | | nearly always use a coil-over spring. In other words, |
| changing the air pressure inside the forks. Valves at | | | | the spring for the rear suspension is a coil spring that |
| the top of the forks allow air to be added or | | | | is installed over, or around, the shock. |
| released from the fork. More air pressue gives more | | | | In terms of adjustment, rear shocks span the range |
| preload, and vice versa. | | | | from pre-load adjustments only to racing shocks with |
| Preload on bikes without adjusters can be changed | | | | adjustments for pre-load, and four different kinds of |
| by disassembling the fork and changing the length of | | | | damping. Most shocks have internal oil resevoirs, but |
| the spacer between the top of the fork spring and | | | | some have external ones, and some offer |
| the fork cap. A longer spacer gives higher pre-load, | | | | air-assisted damping. |
| and vice-versa. | | | | A number of companies offer custom-built rear |
| The pre-load on both forks should always be the | | | | shocks for motorcycles. These shocks are assembled |
| same. Dangerous handling characteristics and possible | | | | for a specific motorcycle and rider combination, |
| mechanical damage can result otherwise. | | | | taking in to account the characteristics of the |
| Damping adjustment | | | | motorcycle, the weight of the rider, and the rider's |
| Some stock telescopic forks have external | | | | preferred riding style/aggressiveness. |
| adjustments for damping. The adjuster is either a dial | | | | Twin shocks |
| or a knob slotted for a screwdriver. Turning the | | | | On motorcycles with twin-shock rear suspensions, |
| adjuster turns a rod inside the fork which brings | | | | there is a shock on each side of the swingarm, which |
| different sized orifices into alignment with the | | | | connects to its respective side of the motorcycle's |
| damping fluid flow path inside the fork. Smaller | | | | frame or subframe. There are no linkages between |
| orifices restrict the flow of the fork oil more and give | | | | the shocks and the swingarm or frame. |
| greater damping, and vice versa. | | | | It is important on twin-shock motorcycles that both |
| This adjustment is either for compression damping | | | | shocks be the same, and that if they are adjustable, |
| alone, or for both compression and rebound damping. | | | | that the adjustments on both sides be the same. |
| Fork oil | | | | Otherwise, there can be a torque to the swingarm |
| Since forks act as hydraulic shocks, changing the | | | | which may cause dangerous handling and braking |
| weight of the fork oil will change the damping. Higher | | | | characteristics. |
| weight fork oil will give more damping, and vice versa. | | | | Mono-shocks |
| Fork oil collects impurities over time and should be | | | | On a motorcycle with a mono-shock rear suspension, |
| changed periodically. A motorcycle's manual will give | | | | there is only one shock that connects the rear |
| guidelines on how often the oil should be changed. | | | | swingarm to the motorcycle's frame. Typically this |
| Decades ago, it was often recommended to use | | | | lone shock is in front of the rear wheel, and uses a |
| ATF (automatic transmission fluid) as fork oil. | | | | linkage to connect to the swingarm. |
| Currently most sources recommend using an oil | | | | Mono-shocks eliminate torque to the swingarm and |
| specifically designed to be used as fork oil, such as | | | | provide more consistent handling and braking. They |
| Bel Ray's. | | | | are also easier to adjust, since there's only one shock |
| Cartridge forks | | | | to adjust, and there is no worry about matching two |
| Cartridge forks use internal cartridges with various | | | | shocks. |
| leaf springs covering orifices to control the damping | | | | Honda refers to its mono-shock designs as Pro-link |
| of the fork. | | | | suspensions. |
| Some of the leaf springs lift with little force allow fluid | | | | Pre-load adjustment |
| to flow through the orifice. Other springs require | | | | The pre-load on a rear shock is typically adjusted via |
| greater force to lift and allow flow. This gives the | | | | a threaded or notched collar on the shock. As the |
| fork progressive damping, allowing it to be stiff over | | | | collar is rotated, the coil-over spring is compressed |
| small bumps, but get softer over larger bumps. | | | | more or less. The more the spring is compressed, the |
| Also, the springs only allow flow in one direction, so | | | | higher the pre-load, and vice versa. |
| one set of springs controls compression damping, and | | | | Some shocks, known as air-assist shocks, allow |
| another rebound damping. This allows the dampings | | | | adjustment of preload by changing the air pressure |
| to be set separately. However, changing the settings | | | | inside the shock. A valve on the shock allows air to |
| requires disassembly of the forks. | | | | be introduced or released from the shock. More air |
| Cartridge emulators are aftermarket parts that make | | | | pressure gives more preload, and vice versa. |
| non-cartrdige forks behave like cartridge forks. | | | | On motorcycles with twin shocks it is very important |
| Brake Dive | | | | that both shocks have the same pre-load. Dangerous |
| When a motorcycle brakes, weight is transferred to | | | | handling and braking characteristics can result from |
| the front wheel, just like in any vehicle with a | | | | dissimilar pre-load adjustments. |
| suspension. This is similar to the feeling of leaning | | | | Damping adjustment |
| forward when you brake hard in a car. | | | | Stock rear shocks typically offer no damping |
| That added weight to the front wheel is transmitted | | | | adjustment, or a single adjustment for both |
| through the forks, which compress under the | | | | compression and rebound damping. This adjustment is |
| additional force. Since the wheel is at the same level | | | | usually made by a dial at the very top or very |
| (the road hasn't gone down), the shortening of the | | | | bottom of the shock. The dial selects one of a few |
| forks causes the front end of the bike to move | | | | different orifice sizes for the damping fluid flow path. |
| lower. This is brake dive. | | | | The larger the orifice, the less the damping, and vice |
| Brake dive can be disconcerting to the rider, who | | | | versa. |
| may feel like he or she is about to be thrown over | | | | On motorcycles with two rear shocks, it is very |
| the front the motorcycle. If the bike dives so far as | | | | important that the damping on both shocks be set |
| to bottom out the front forks, it can also cause | | | | the same. Dangerous handling and braking |
| handling and braking problems. One of the purposes | | | | characteristics can result from dissimilar damping on |
| of a suspension is to help maintain contact between | | | | the rear shocks. |