Like any other vehicle or object, your motorcycle is subject to the laws of physics that govern our universe's behavior. Gravity, friction, Newton's third law of motion (the one about equivalent and opposite reactions) – all these forces act on your bike.
What makes a motorcycle unique is a simple, basic, defining fact: motorcycles only have two wheels and cannot stand on their own. This sets motorcycles apart from cars and other vehicles and changes how the laws of physics work on the bike. The need for balance comes into play every time we jump on our bikes.
A series of powerful forces come into play when we start riding. One of the most dramatic examples of these forces and how we can bend them to our own will comes every time we take a curve. When we lean into a ride, we actually manipulate our own mass to balance the cycle between gravity that pulls it toward the ground and the centrifugal force pulls it up. A bit too much of our weight is thrown in some way and we are inadvertent. Gravity wins in this case.
Resistance and friction
The greatest resistance to the engine of a bike and thus slowing you down is aerodynamic drag. Wind resistance is the most important factor your bike must overcome to keep you moving forward with speed and fuel efficiency. This is why many motorcycles are designed with aerodynamics in mind, eg. through the introduction of birds, which reduces traction and improves fuel consumption.
The other great force that your bike has to overcome is the friction between the tires and the road. In the car and motorcycle context, we call friction "traction". The heavier you and your bike, the more friction you generate. This explains why the front brake of the motorcycle works more efficiently than the rear. As you slow down the distribution of weight transfers to the front tire, increasing its traction. At the same time, the rear tire carries less load and has less traction.
When engineers design the amount of treads on our tires, they need to strike a balance between the grip and the ability to handle different road conditions. Fully smooth tires provide the most grip, but are prone to hydroplaning on a wet surface, so tires are designed with channels to remove water and lower the hydroplaning risk. So each motorcycle tire represents a compromise between smoothness and tread depth.
Every time you lean into a curve, you are motor-driven. This is a torque-controlled control in the opposite direction from your turn that initiates your tilting process. In fact, without this little movement before a turn, the laws of physics would not let you lean in the right direction, and therefore you would not be able to turn at all.
When most people think of physics, they tend to think about space, the Large Hadron Collider and other high-fall routine. It is fascinating to remember that many of these same forces act on us, even in our everyday lives and activities.