Intrigue is often accompanied by gossip, speculation and myths. But we want to know what and how many truths are in the tales and how many fantasies? Therefore, at the same time I will try to dispel some of the myths that arose around motorcycle suspensions.
“Why improve what is already perfect? - many will be surprised. “After all, even with standard settings, Japanese sports bikes are ten orders of magnitude better than any scooter!” There are several reasons. First of all, it must be clearly understood that at the factory the suspension is adjusted to a certain “average” pilot weight, and because you are heavier or lighter than this “middle weight”, the tuning will be optimal for you. The second reason to "prank" the settings - riding with a passenger and / or with luggage. Remember how the headlight turned into an anti-aircraft searchlight when you were traveling with a passenger in the dark? Or how did you “break through” the rear shock absorber while driving with the same passenger in potholes?.. Another reason to “conjure” is your attraction to active driving and competitive races, and when you “bullet”, the standard settings are your enemy. But more about that later.
Ideal comfort for the pilot comes when the suspension "fulfills" absolutely all the bumps in the road, absorbs the blows that a motorcycle and, naturally, a pilot could receive. But the trouble is, the same potholes or asphalt growth at different speeds lead to a shake of different strengths: potholes come in different heights, depths, longitudinal and transverse, of one form or another. And they are scattered on the road in a picturesque mess. All this leads to a huge range of suspension movement speeds - from a small one (say, on asphalt with smooth "waves") to a giant one (when hitting a serious pothole the size of a "lying police officer"). Can you imagine how difficult the task is? Indeed, the characteristics of most shock absorbers are constant (if you do not take into account their fluctuations due to changes in temperature and wear, and also do not consider more modern shock absorbers with separate damping adjustment for different speeds of the suspension) and are designed for a narrow range of suspension speeds. This contradiction leads to the conclusion: there is no universal setting that "works" equally well in any conditions.
But besides the impact of potholes, there are still greater forces to be reckoned with. We are talking about the redistribution of weight on the front or rear wheels (through the fork and rear shock absorber) during acceleration and braking. These forces are so significant that the energy of strikes against “average” potholes cannot be compared to them. An example of extreme weight transfer is a Willy or Stoppie, in which 100% of the mass of a motorcycle is redistributed to the rear or front wheel. So that the fork and the rear shock absorber can cope with such tortures, they are tuned much harder than necessary for a comfortable ride. Therefore, on many modern motorcycles, especially on sportbikes and street fighters, the convenience of the part of the pilot’s body responsible for “perseverance” has been sacrificed for handling.
The first step in setting up the suspensions is to adjust the preload of the springs and the height of the suspension. Before telling how this is done, we will figure out what exactly regulates the preliminary preload of the springs.
In working condition (with the pilot sitting on the motorcycle in full uniform), the suspension must be configured so that it is not fully compressed or unclenched - otherwise it can only work “one way”. The ratio of the distance over which the suspension is compressed under the weight of the motorcycle and the pilot to the full length of the suspension travel is called the static drawdown of the motorcycle. By changing the preload of the spring, we change the static subsidence, i.e. we choose which part of the suspension travel is responsible for compression, and which part is responsible for rebound. And at the same time, we change the weight necessary to completely compress the suspension (attention: stiffness does not change at the same time!). The optimal static drawdown should be within 25-30 percent of the total suspension stroke length.