Know how to brake
Adhesion, mass transfer, sequencing, descent: what to do to stop well
Read even if you have a car equipped with ABS!
A recent road safety companion emphasizes that the motorcycle brakes less well than the car (at 50 km / h the motorcycle stops at 20 meters versus 17 for a car, while at 90 km / h the motorcycle stops at 51 meters when the car only needs 43,3 meters). Again, these numbers are further expanded by other studies.
A statement that surprises many bikers, who often pride themselves on the immediate bite of their radial stirrups. However, this is quite true, at least according to the laws of physics. Because at the end of the dynamic brake chain, we simply find the tire, which we push (very) hard on the ground ... Explanations.
Tire compressed on the ground
A tire placed on the pavement is subject to resistance when asked to move: this is good news and bad news, as this handle guarantees handling, but at the same time requires fossil (or electrical) energy to move forward. Of course, the level of grip varies depending on the type of surface and weather conditions, but this aspect of things has already been discussed in our tips for driving in the rain.
Therefore, in order to slow down, you must apply force to the tire. The tire body is designed to deform slightly when subjected to certain forces, in this case a longitudinal force. Therefore, for optimal carcass performance, care must be taken to ensure that the tire is inflated in accordance with the manufacturer's recommendations. By the way, when was your tire pressure last checked?
Front or back?
Under the effect of deceleration, the transfer of charge will occur in the opposite direction of the forces or logically forward. Thus, the weight distribution, which is on the order of 50/50 statically on most bikes, will change and the ratio of the motorcycle will shift sharply forward, in proportions of 70/30 or even 80/20.
Be aware that in MotoGP we record up to 1,4 Gs during heavy braking! This is not on the road, but it illustrates how force exerted the braking conditions and also shows that a lightly loaded tire will have no grip and therefore little deceleration, resulting in light rear wheel locks. This does not mean that you should not use the rear brake: you just need to use it wisely and understand its role.
Ideal braking sequence
The optimal braking sequence is as follows:
- First, start carefully with the rear brake: since the motorcycle will apply force primarily to the front drivetrain, starting at the rear will stabilize the bike by compressing the rear shock slightly. This is even more important if you have a passenger or luggage.
- in a split second, apply the front brake: acting on the rear, applying a little more pressure to the entire bike on the ground, the overall level of grip will increase significantly, allowing this large movement to be triggered by transferring the load to the front tire.
- in a fraction of a second will put more pressure on the front brake: the front tire is now loaded, it can be tight and take all the maximum deceleration force, at which time the rear brake becomes useless. It is during the transfer of the load that the braking capacity can be used in optimum condition. Conversely, abruptly applying the front brake without first performing this load transfer presents a high risk of blocking, since we will severely strain a tire that is not optimally loaded.
Obviously, bikers who have a car with coupled braking, ABS and splitter will never know this feeling of fullness brought on by perfect braking skill, which is an art form. On the other hand, they are also less likely to get stupidly drunk when braking badly.
From theory to practice
If the theory is universal, the poetry and beauty of the motorcycle world lies in the diversity of its representatives. Thus, each car will have optimal braking within the partial cycle elements, which are due to the internal load capacity of the tire (the maximum force that the carcass and rubber can withstand), and especially the ability of the chassis (frame and suspensions) to accurately transfer braking forces without dissipating into parasitic effects.
Thus, a motorcycle with a poor fork or with a tired suspension (hydraulic that has lost its viscous capacity) is not only inconvenient: it is also less safe due to degraded braking capacity, since its wheels will not constantly have good contact with the ground, so they will not will be able to transmit significant braking force.
As an illustration, a sports car with a short wheelbase and a solid inverted fork, the stiffest elements of which are attached to other equally stiff elements (solid aluminum frame) and placed on soft rubber tires (thus heating faster in favor of traction), puts all sliders great However, the short wheelbase and high center of gravity will easily cause the rear landing gear (which the pilot can counteract by moving slightly along the rear of the saddle). Therefore, it is this tipping point that represents a possible deceleration limit rather than a grip on the front tire that would simply fail with bad asphalt in the rain. (The athlete can stop on wet roads!)
And vice versaThe custom with its long wheelbase and low center of gravity won't tip over easily. It can even brake harder than a sports car, provided you have good brakes and high performance tires. But thanks to the traditional small fork, poor front brake and mostly rear weight, it is not equipped to put heavy loads on the hard rubber front tire. Its stopping power will rely heavily on the rear brake, with less risk of blockages than a more conventional motorcycle as the rear axle is heavier. And with the idea of better resistance to the braking forces of the rider, the arms will be extended and extended. When you do push-ups, the hard pass is when your arms are bent, not when they are outstretched!
And ABS in all this?
ABS has the safety of limiting the main risk of braking: wheel blocking, an increased source of risk of falling and shame when you end your trajectory on your stomach (or back) in general fun. But just because you have ABS does not mean that the confidence provided by this app leads to the inhibition of the same interest as the chicken against the Rubik's cube, and that we should not learn to slow down, because ABS does not reduce braking distances... In some cases, it can even lengthen it. This helps to maintain control.
Whether packed with electronic chips or not, the bike complies with physical laws and compliance with the rules optimizes the whole operation.
Likewise, having ABS does not free you from knowing how to “read the road,” which is a vital reflex for any biker. Some generations of ABS do not like bumps (the power plant is not folded enough to integrate chassis movements) and tend to "release the brakes" and give its driver a great moment of loneliness, while on some departmental roads bituminous compounds can have different levels of grip. Therefore, an experienced biker should read the road (or track) well.
Of course, the latest generations of ABS are getting more and more efficient, and today some systems (and some motorcycle brands) offer absolutely amazing efficiency systems and have even become programmable according to the driving style. But the ABS offered on entry-level roadsters a few years ago was perfect, not to mention the ABS from the early 1990s, which is not advisable to stop vigorously as a bumpy, bumpy smooth transition is approaching or you will fit Michelin!
Thus, having ABS does not free you from knowing these rules and applying decreasing braking: mass transfer, then you apply the brakes and release the pressure in the final stage as you approach the entry into the corner. This prevents the tires from being subjected to both centrifugal and braking forces. Otherwise, as a result of these two efforts, there is a high risk of breaking the tire's grip ellipse ... And patatra ...
Should we downgrade?
Why not! In the context of early braking, lowering will restore a little load to the rear tire, so help stabilize the bike before mass transfer. You just have to consider the engine performance: you don't retrograde as much as with mono or two, as with three or more.
In the event of emergency braking, downshifting is useless, and in any case, if it's really urgent, you won't have time. It's too much to drive, and in real emergency braking, you don't touch the selector.
One final tip: exercise and prepare
As the English say, practice makes perfect: To avoid being caught off guard on the day an emergency comes to you (or just discovering a new bike), it is best to exercise. In a parking lot, in a deserted industrial area, in a safe place, no traffic jams. Take time to repeat all the braking phases at your own pace and get a feel for how your motorcycle works. Then increase your speed. Gradually. With hot tires and practice, you will be amazed at the actual stopping power of your motorcycle.
By the way, and the brakes?
You saw we almost gave you an article on braking that didn't talk about brakes. It would be a beautiful literary spectacle: Le Repaire, at the forefront of experimental journalism!
Lever, master cylinder, brake fluid, hose, calipers, pads, discs: the final performance also depends a lot on this device! The condition of the plates is regularly checked and the fluid life is not permanent and it is recommended to change it every two years. Finally, the brake lever fuse will be adjusted to feel perfectly comfortable with this control.
One final tip: Once all of this is mastered and you become a real skilled hunter, watch the vehicles behind you in traffic ... see Tail Machine Gun Syndrome.
