How Bicycle Brake Pads Work: The Science Behind Stopping Power

Ever wondered how tiny brake pads on your bike can bring a rider and their bike to a halt in a quick fashion?

Most people know what brake pads do - they stop your bike. But few understand how they actually work. Beneath every smooth stop and controlled descent is a mix of physics, engineering, and smart material science!

Let's break down the science behind brake pads and what makes some perform better than others. 

 

1. The Basics: Turning Motion into Heat

Remember in science class where we learned that energy cannot be created or destroyed, only converted from one form to another? That's what happens during the braking process! 

When your bike is moving, it has kinetic energy - the energy of motion.

Kinetic energy can be calculated by:

0.5 x mass of system x square of the velocity. 

So we see that the total kinetic energy depends on 2 variables:

1) the mass of the rider and the bike

2) the velocity (how fast you're going). 

The heavier the system mass and/or the velocity, the greater the energy. Velocity, however, has a huge impact on the total energy due to kinetic energy being a function of the square of velocity.

Every time your speed doubles, the total kinetic energy increases fourfold! This is why solid and reliable braking is crucial for long downhill stretches on the bike!

For hydraulic disc brakes which are all too common these days for most bikes, when you pull your brake levers, this pushes brake fluid to:

1. The brake caliper which pushes the pads against the rotor 
2. The friction between the pad and the rotor converts kinetic energy into thermal (heat) energy, potentially even sound energy too (squealing brakes) 😖
3. The rotor and air around it dissipate the heat.

It's a precise conversion process: motion (kinetic energy) > friction > heat (thermal energy) > bike stops.

Too little friction = poor braking.

Too much heat = brake fade, glazed brake pads and even rotor warping!

This is why brake pad design focuses on controlling friction and heat, not just creating it.

 

2. Friction: The Foundation of Braking Power

Brake pads stop your bike through two types of friction:

Adhesive Friction

As your pad presses against the rotor while the rotors are in motion, friction and heat transfers a layer of brake pad material onto the rotors. This is called a transfer layer - imagine road surfaces when a car does a burnout or a drift.

This transfer layer is why it is so important to bed in your rotors properly! Every cyclist with a disc brake bike can attest to how weak the stopping power of disc brakes are until well bedded in.

When braking, this transfer layer momentarily bonds and brakes, slowing your bike down and is much less destructive compared to the other type of friction we will cover: abrasive friction.

Abrasive Friction

This occurs when the pad surface gently grinds against the rotor. It removes a tiny layer of material each time, converting energy into heat. This leads to faster pad wear and rotor damage, but this is the inevitable cost of stopping your bike! The energy has got to go somewhere...

 

3. Heat: The Hidden Enemy

During hard braking, temperatures at the pad-rotor interface can reach up to 250°C!

Example:
A 75kg rider + 9kg bike going at 40km/h carries about 5185J of kinetic energy. In a single instance of braking from 40kph to a full stop as hard as possible, the 2 brake rotors would heat up by ~47°C. This is calculated using the fundamental heat transfer equation 

ΔT=Q/(m×c), where:

• $Q$ is the thermal energy (the kinetic energy of 5185J),
• $m$ is the mass of the rotor (assumed to be 110g), and
• $c$ is the specific heat capacity of the rotor material (assuming stainless steel).

We also assume the braking force is eventually distributed between 2 identical rotors, and there is no heat transfer between the air and rotor system. 

Changing things up, say we brake at 50km/h with the same conditions as before, the individual rotors would heat up by 88°C instead! Remember, this does not accounting for the ambient temperature.

We can see how much of a beating the rotors and brake pads have to withstand, especially over long and fast descents or heavier systems such as eBikes.  

Naturally, the pads and rotor need to manage this heat properly. If not, problems begin:

• Brake Fade: When overheated, brake pad material loses friction, resulting in a sudden drop of braking power. This is why brake pad manufacturers such as Shimano add cooling fins to the brake pad backing. 
• Glazing: This is when the pad melts slightly, hardens, and becomes smooth - reducing grip.
• Rotor Warping: Uneven heat expansion bends the rotor, causing pulsing or rubbing. 

If you've ever seen steel rotors turning yellow/brown/purple/blue, this is a sign that the steel has begun to oxidise, indicating temperatures well over 200°C.

 

4. Balancing It All: Heat, Traction, Control

On a practical level, both friction and heat management determine how well a bike’s braking system performs. But just like in cars, bicycle brakes can’t generate unlimited force or endure extreme temperatures forever.

Even the best brake pads and rotors have limits. Push them too hard, and they’ll overheat, glaze, or fade. But there’s another limit too: traction.

No matter how powerful your brakes are, they can only stop as effectively as your tires can grip the road or trail. If braking force exceeds traction, the tyres will skid or lose grip, which reduces control and increases stopping distance.

That’s why a good brake system isn’t just about raw stopping power. It’s about the balance between:

• Generating enough friction to stop quickly and safely
• Managing heat so the brakes stay consistent, and
• Matching that power to the tyre’s ability to maintain grip.

From a design perspective, modern bicycle brakes are all about this trade-off. The goal is to deliver maximum braking performance without sacrificing control or stability, no matter the conditions - dry asphalt, loose gravel, or wet downhill trails.

 

5. Brake Pad Materials

Given the wide variety of situations one may find themselves and their bikes in, manufacturers have created a selection of brake pads formulated with different compounds, each type more suitable for a certain riding characteristic than the other. 

Brake pad compounds can be formulated using an extremely wide variety of compounds, which is why every brake pad manufacturer guards their unique recipe!

To read more about the general different compounds used, click here! 

 

6. Final Thoughts 

Braking isn’t just about force—it’s about control, consistency, and confidence. Behind every smooth stop lies a balance of physics and material design.

Your brake pads manage that balance every time you ride. So when it’s time to replace them, choose pads designed with real science behind them. Because when it comes to stopping power, you need brakes that you can trust.

Discover TracEdge Brake Pads - Made by experienced Taiwanese engineers involved in the designing and manufacturing brake pads for the automotive, locomotive and agricultural sectors!

 

With ❤️,
Tim