Front suspension: how the telescopic fork works

In this article we will treat the technical and operational details of the telescopic fork suspension systems, this type of suspension is the most common and currently used in most motorcycles for the front in the custom models, sports motorcycles, Offroad ...
Its success is mainly based on its simplicity and effectiveness, ease of maintenance, rigidity and reasonable cost.

SUSPENSION: MORTIGUATORS AND SPRINGS
The suspension system is part of the chassis of the motorcycle, specifically of the elastic part of the same, and its main mission is to absorb the irregularities of the road, allowing the vertical movement of the wheel to keep the contact with the ground at all times and at the same time enabling driving under control and comfort of the driver and passenger.

To better understand how the system works we will explain the damping sequence:
-In a first moment the irregularity of the soil is absorbed by the deformation of the tire, it is therefore that at the technical level the tire is also considered as part of the damping.
-Once the tire was compressed, the force exerted continues to push, compressing in turn to the suspension dock. The spring can be linear or progressive, the latter has the space between turns or "pitch" gradually reduced to make the beginning soft and harden progressively.

The spring is tense at the same time that it is compressed, absorbing the energy of the impact and allowing the motorcycle chassis to follow as horizontal as possible with respect to the ground.
In rest position we can regulate the hardness of the spring, either replacing it with another more rigid or long or compressing it more, this is called compression adjustment.
-When we pass the obstacle the force exerted decreases and the spring tends to recover its original length, releasing the energy and pushing back to the wheel down, so as not to lose contact with the ground.
In this basic way what would happen after going through a bump is that the motorcycle would begin to bounce without control, so you have to add some energy absorption system to be able to control the spring movement: the shock absorber, which converts this energy In friction and heat.
In the case of the shock absorber, it is formed by a piston with holes through which a special oil passes, modifying or adjusting both the quantity and size of the holes and the oil density can regulate the speed with which the dock will rise or It will go down, that is, compression and extension.

This is why the telescopic fork is a hydraulic suspension system.
There are many types of hydraulic valves or pistons, totally mechanical, fixed or adjustable, and also of electronic adjustment.
Fork oils are classified according to their viscosity, the more “hard” damping.

Telescopic fork types
When classifying this type of suspension we can talk about conventional fork and inverted fork.
-In the conventional fork the mobile part is the lower bottle, which slides down the bar subject to the typical.
-The inverted fork is basically a conventional fork mounted "vice versa", where the bottle is at the top, subject to the shell, and the bar slides inside it. Although more expensive to produce, it offers better results since the "non -suspended mass" of the front train decreases, that is, the weight of the components that rise and fall with respect to the chassis, eliminating inertia and improving driving.

At the internal functioning level, telescopic forks can be classified as:
-Conventional: In this type of suspension we have the dock and the piston with its holes (fixed or adjustable), as we have explained above.
-On cartridge: it is an evolution of the previous system, and it is like having "a shock absorber inside the shock absorber." The main advantage of the cartridge is its high -speed circuit, when for example we take a fast pothole that the damping system cannot absorb because the oil cannot pass so fast through the piston holes, the cartridge enters action by opening a step that allows you to release the pressure, keeping control at all times.
In these systems, used, for example, in the Harley-Davidson Touring, Buell and some Sports Models, the suspension can respond efficiently to a multitude of driving situations where a conventional system would reach its limits.

Improvements and modifications
Although on another occasion we will talk about the correct maintenance and adjustment of hydraulic forks, here is a couple of "inventions" that greatly improve conventional systems, especially in custom models. The user profile of these motorcycles will not demand great sports performance, so manufacturers usually lower costs in this important component.
-"Gold Valves" or emulators: it is an extra piston that is added to the system, simulating the behavior of a cartridge system. They are relatively economical and adjustable.

-Tart-on "cartridge system: in this case it is about converting our conventional telescopic fork into a cartridge suspension, you just have to extract the original components and" drop "this new system to obtain a high performance suspension.

Frank Burguera

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