Two years ago, I posted on the Italian channel one video where I found myself without brakes with the BMW
1000 at
260 km/h,
I was very lucky because the runway was so long and
For the first part of the braking, I actually had a 20% of the braking power
So I was able to slow down but in that video
Many people in the comments asked why didn't you just brake with the rear brake?
I mean I did but many of you probably know that the rear brake brakes much less than the front brake. But why is that?
Why do every motorbike and every street car has very big front brakes and very small rear brakes?
So that question gave me the inspiration for this video in which I'm going to explain
Why the front brake brakes much more than the rear brake
So as always when I explain something about physics
I
Explain it in a simple way so that even my grandmother is able to understand this video and that's because the goal of this video
Is not to give you a degree in physics
but to take concepts that are usually complex and make them understandable to all so when a
Motorcycle is going at any speed the physical principle of inertia applies
Meaning that a mass that is in a state of rest standstill or in a state of straight uniform motion
So it means it's going straight
Maintains its state. What does it mean?
It means that if the motorbike is still it remains still while if it's going at 100 and you release the throttle it
Tends to remain at 100
Well actually on earth if you release the throttle and you are at 100 the bike starts to slow down because of the engine brake
the friction of the air, of the tires
But if you're floating in the empty space, it will go at 100 forever
So due to the principle of inertia when there is a mass which is moving and you want to slow it down
The mass will oppose resistance
So what happens when you break for example with the front brakes when you pull the lever?
the brake caliper tighten the disc and
Slows the rotation of the front wheel
But this itself is not enough to slow down the bike because if you were floating in space and pull the brake lever
You simply lock the front tire and you keep going at 100. what really slows down
The bike is the friction between the wheel and the asphalt
So let's recap: you pull the brake lever
The caliper tightens the disc the wheel would like to block but due to the friction of the tire with the asphalt
It keeps rolling, but the friction of the caliper on the disc slows down the rotation
So the bike slows down
So this friction translates into a force applied
At the asphalt level that goes in the opposite direction of the movement. you can imagine it as if
Someone is pulling the bike from the spot where the wheel touches the ground
however
we must not forget the principle of inertia that I mentioned before for which the bike which is going forward and which
Would love to continue to go forward
Opposes braking with an equal and opposite force and we identify this force as a green arrow
But where is this force applied? Where is this arrow Actually?
it is not at ground level, but we can put it at the level of the bike center of gravity
Which is the midpoint of all the bike's weight
now the fact that these two forces are not at the same level is
Fundamental for this video and now you're going to understand why. take as an example
Any object like this box and we will replicate our forces on the box
We have a force, the braking, the red arrow
Which pushes to one side at the ground level and we have another force which is the inertia, the green arrow in the center
of gravity, which pushes in the other direction now, I apply the forces and
Voila the box flips over. the same exact thing will apply to the bike: the bike would flip forward
So they invented the suspensions. this roll over is damped by the suspensions and the bike instead of flipping over
Compresses the front suspension and releases the rear suspension, a so-called weight transfer is applied to the front wheel
Most of the bike weight is loaded on the front tire, while The rear wheel is lightened. Now,
I will explain this last fundamental concept that will allow you to understand totally the video
Look at this rubber: if I simply put it on the table and push it, it slips on the table
But instead if you press it hard towards the table and try to push it it stays in place
This is given by the law of friction
which says that the stronger the force perpendicular to the plane the stronger the friction is
so if we bring this force to our bike we have for example that the rubber of the example is
Represented by the tire while the strength of my arm is represented by the weight on the tires
So the more I brake the more weight
is transferred to the front the more the weight on the front wheel increases the more friction this wheel has on the asphalt and
The more that wheel can brake hard and what happens in the rear
That's the opposite the more I brake the more the load moves forward the more the weight on the rear
decreases
the more the friction that the rear tire has on the wheel decreases and
The less that wheel can brake and if you look at the extreme cases
They clarify your ideas even more because if I brake too much and the rear will lift
It means that the hundred percent of the weight is on the front wheel
So this suggests that while braking we may arrive with the point where the rear brake becomes totally useless
So this is the reason why on the motorbike and on cars and on any vehicle
The front brakes are much bigger and stronger and more powerful than the rear brake
and for this reason it's almost impossible to brake hard with the rear brake because the more we brake the
more the front wheel gains braking power while the rear wheel loses braking power
But according to this logic if the bike goes in Reverse, it will be the rear brake the most powerful one
But if you want to understand it
You may try to take a bicycle and try to go forward or back and see the difference with the braking
So to answer those that asked me why didn't you break with the rear brake when you found yourself with no brakes?
the answer is I actually broke with the rear brake but
it takes
So so long to slow down the bike when you are at 260 km/h for example in this video
you can see a rider from the Italian championship which found himself with 0% front braking in mugello at
270 km/h, so
He slammed on the rear brake. He started down shifting, but he didn't really slow down that much and this is what happened
so all of this thing about brakes
happens because the braking force and the inertia force are not on the same level and
So they lead the bike to overturn
So this means that if the braking were not bound to the ground
it could also be put behind, one example is the parachutes that are used to slow down the space shuttles and
Considering that these shuttles are not bound to the ground, They are placed behind the shuttle. So that's it
I hope you enjoy this kind of technical videos if you like them
Please let me know in the comments and let me know also what you would like to see in the next videos
Once again, thanks for watching. Don't forget to subscribe and see you in the next video. Bye. Bye