A Motorcycle Braking Guide: Part 1
We should admit that motorcycles have always been associated with high speeds, no matter if we're thinking about merely passing the legal limits or traveling at bullet-speed along a free highway. Most bikes come with tremendous acceleration capabilities and some even go way beyond the point of safety, as acknowledged by experienced riders.
While picking up speed is fairly easy when riding a motorcycle, braking in time to avoid crashes, pass various obstacles or enter a turn safely can be a matter of life and death. Being able to slow down or come to a complete stop in the most demanding situations or inclement weather is a very important skill bikers should develop and constantly exercise throughout their riding career.
In this first episode of the braking guide, we are going to shed some light on few terms and describe the basic principles of motorcycle braking. Further articles will go deeper in the matter, for better and clearer info.
First of all, braking is directly related to grip. In simple words, the grip is the friction between your tires and the surface you're on. This friction is a part of the mechanism that allows you to go forward as you thrust the gas, keep your lane when cornering or stop when needed.
A bike's grip depends on a lot of other factors, such as the physical condition and type of tires you're using, the nature of the road's surface, the presence of debris or water. Old tires or tires improperly chosen for the road you plan to travel affect grip in a negative way, rendering the bike prone to skidding and increasing the braking distance.
Likewise, wet asphalt or a road covered in snow mean less grip and increased chances to skid. It is crucial that riders get a good idea of their bikes' grip and road contact; getting to know your bike also boosts the confidence and allows the pilot to drive a bit more relaxed.
Lightweight bikes, on the other hand, tend to lose contact with the road easier and thus can skid much quicker than the heavy motorcycles. Keeping this in mind will also help you decide upon your riding style when switching bikes.
Due to the very constructive nature of a motorcycle, the weight shifts to the rear or to the front as you accelerate or brake. Since grip is drastically influenced by the weight, your bike's stability and road contact will vary accordingly; while revving the gas, the weight is pushed towards the rear, pressing the tire harder against the road and ensuring better grip provided you're not exaggerating with the throttle.
Easing your hand on the throttle creates engine braking, as the bike tends to slow down, re-establishing the weight distribution; and if you hit the front brakes just a bit, you'll instantly feel the weight of the bike (and your own) being pushed to the front, causing what riders call “a dive”. Now much of the weight pushes hard on the front tire, maximizing the grip and helping you slow down as you squeeze the brake lever. Yet, never forget that in these moments the rear wheel is lighter and can slip easy enough; we'll cover this issue later on.
If you look at any motorcycle and see the very small contact surface between the tire and the road - even more, just think about an even smaller one as the bike is moving - this surface is all you can use to slow down or come to a halt and using it wisely can make the difference between returning home safely or bruised. Or not returning at all.
As braking is not a “natural skill” like countersteering is, it needs both practice and observation. Keeping an eye on what's below your wheels can give you a lot of information about how you should ride to make it to your destination in one piece; failing to watch out for the changes in the road condition can put you in dangerous situations where you can suddenly lose grip and maybe spill.
Not noticing the gravel or sand in a turn and entering that corner leaning too much and with too much speed is one proven recipe for having one wheel or even both losing grip and sending bike and rider(s) skidding out of control.
Chapter punchline: remember that grip is the key element that makes you go faster and it is crucial to slow you down and bring your bike to a stop safely.
The Brakes Themselves
Bikes come with front and rear brakes and they're meant to be used simultaneously for the best results. The weight shifting described above is one of the most important reasons to use both brakes; braking correctly compensates for the different bike balance induced by the dynamic changes and helps keeping both wheels down.
The basics of the weight-shifting are quite simple: accelerate and the weight moves to the rear wheel, brake and the weight moves towards the front tire. What's even more important is the complementary effect: as the weight goes to the rear wheel, the front one tends to lift and lose grip; in case you throttle hard, you can completely raise the front wheel off the road and “pop a wheelie”.
When braking hard, it's the rear wheel that tends to lose grip and could send the bike in a side-skid if no countermeasures are taken. In order to minimize the grip loss and rear wheel lift effect, you must press the foot brake; doing so compensates the weight shifting and balances the bike.
Most experienced riders agree that braking should begin with gently pressing the rear wheel lever followed very shortly by the main stopping force of the front. When it comes to braking and stopping, the front brakes provide between 60 and 80 percent of the needed force. In case this kind of math seems weird, let's analyze the very facts.
1. You brake, the weight shifts to the front and pushes the tire into the road. Result: better grip.
2. The front wheel has two brake discs. Result: double the force opposing the bike's inertia.
3. The front brake discs are usually larger in diameter than the rear ones. Result: more stopping force.
Even with these three reasons (out of many more possible), the crucial importance of front wheel braking should be now perfectly highlighted.
Little does it matter if we think about braking at high speed or a slower one: the process is the same, as the very laws of the physics do not change. When riding very fast and looking just to slow down to a more “reasonable” speed, you could just use the front brake with caution. But in case you need to stop your motorcycle in the shortest distance possible, initiating braking with the rear wheel is mandatory.
Why is it so? The very dynamics of the bike have a very simple explanation: braking with the rear wheel already adds some weight to the front and you can squeeze the front brake lever a bit harder with less dive, allowing you to slow down faster.
Modern-era motorcycles come with AI-assisted braking that engages both brake pumps simultaneously. It's the LBS (Linked Braking System) or the CBS (Combined Braking System) to which we'll dedicate a whole chapter later on. In few words, the CBS bike will also brake (with a specific force) with the rear wheel when squeezing the front lever, and vice-versa. The electronic aid makes the slowing/ stopping safer and faster and compensates for the human error factor.
Chapter punchline: newbie riders should always keep in mind that correct braking involves using both the front and the rear wheels, rear brake first. Learning to “feel” their bike's brakes and weight-shifting effect helps a lot.
Read more on this subject in the second episode of the guide: A Motorcycle Braking Guide: Part 2.
comments written so far
The disconnect in your article about forward weight transfer lessening grip at the rear and then telling the reader to brake harder with the rear is concerning! The more weight transfer forward, the lesser force required to lock the rear. Surely that self evidently explains why your statement is dangerous??
Also, front end dive does not only occur due to weight transfer. When you resolve the front brake reaction forces into the direction of the forks, there is a component that acts to compress the forks, so dive is both a matter of weight transfer AND resultant reaction force. In a standard fork set up you can't get away from dive. Applying rear brake squats the bike a little, lowering CoG, increasing the wheel base and resulting in greater stability and some additional resistance to a "stoppie" - but the harder you brake, the more dive you experience, the more weight that transfers forward, and the less effective the rear brake becomes. This is evident in late hard sports braking on the track or twisties where the rear becomes air born or very light.
This article requires revision.