The Ultimate Guide to Hydraulic Disc Brakes

Hydraulic disc brakes have transformed modern cycling. Whether you ride downhill, enduro, full power electric mountain bike, gravel, road or commuter bikes, hydraulic brakes allow riders to brake later, control speed more precisely and manage steeper terrain with far more confidence than older cable systems.

But hydraulic brakes are often misunderstood. Brake pads do not create hydraulic power on their own. The hydraulic system creates the clamping force, while the pads control how that power is applied through friction, heat behaviour, feel, noise and consistency.

How Hydraulic Disc Brakes Work

A hydraulic brake works by transferring force through an incompressible fluid. When you pull the brake lever, a piston inside the master cylinder moves fluid through the brake hose towards the caliper.

That pressure moves the caliper pistons, pushing the brake pads into the rotor. The friction between the pad compound and rotor slows the wheel down.

The hydraulic system creates the force. The pads control how that force feels and behaves.

Main Parts of a Hydraulic Brake

What Actually Creates Brake Power?

Brake power comes from the complete brake system, not one individual component.

• Lever leverage ratio
• Master cylinder piston size
• Caliper piston area
• Rotor diameter
• Rotor thickness and thermal mass
• Pad compound friction coefficient
• Caliper stiffness
• Brake hose expansion
• Bleed quality and fluid condition

This is why two brakes using the same pads can feel completely different. A powerful hydraulic system with a poor pad compound can still feel inconsistent, while great pads cannot fully compensate for a contaminated or poorly bled brake.

Understanding Lever Stroke

Open Systems and Compensation Ports

Almost all modern hydraulic bicycle brakes use an open system with a reservoir or bladder to compensate for fluid expansion, temperature changes and pad wear.

The compensation port is critical. It allows the system to equalise when the brake is released. Once the lever is pulled and the port closes, hydraulic pressure can build.

If the port closes too late, the brake can feel vague with excessive dead stroke. If it closes too early or becomes blocked, the brake may drag or lock as the fluid expands with heat.

Caliper Pistons and Seal Rollback

Most modern MTB, electric bike, gravel and road brakes use opposed pistons, meaning pistons move from both sides of the caliper and apply pressure evenly across the rotor.

More pistons do not automatically mean more power. Total piston area, caliper stiffness, piston distribution and pad support are often more important than piston count alone.

The square profile piston seal also helps retract the piston when the lever is released. This is known as seal rollback. Too much rollback creates a long lever throw, while too little rollback can cause brake rub.

DOT Fluid vs Mineral Oil

On smaller screens, swipe across the table to see all columns.

Never mix DOT fluid and mineral oil. The seals inside the brake are designed specifically for one type only.

Brake pad materials and compound choice

Organic or resin, semi metallic, ceramic and sintered describe material families. The complete formulation determines braking feel, temperature behaviour and wear resistance. Choose using the specific compound’s intended use and test results.

Our three ranges are Enduro Pro, Factory Racing and Performance. For demanding electric bikes, heavy cargo bikes and long descents, our recommendations are Enduro Pro Ultimate and Enduro Pro Semi-Metallic. Sintered is our go to Performance compound for wet and muddy riding on conventional bicycles.

Read about brake pad materials and backing plates

Explore Gorilla Brakes pad ranges: Mountain Bike Brake Pads, electric bike Brake Pads, Gravel Bike Brake Pads and Road Bike Brake Pads.

Why Bedding In Matters

Bedding in creates a controlled transfer layer between the brake pad and rotor. Without proper bedding in, brakes can feel weak, noisy, inconsistent or grabby.

This is especially important when changing from one compound type to another, such as organic to sintered. The old transfer layer on the rotor may not match the new pad material.

For more setup help, visit our Installation & Maintenance page.

Brake Noise: Pads Do Not Make Noise on Their Own

Brake noise is vibration. That vibration usually comes from inconsistency somewhere within the braking system.

• Contaminated pads or rotors
• Uneven piston movement
• Poor caliper alignment
• Incorrect bedding in
• Rotor thickness variation
• Air in the hydraulic system
• Loose hardware

Some compounds can amplify noise more than others, especially harder metallic compounds, but the root cause is usually vibration or contamination somewhere in the system.

Rotor Size, Thickness and Heat Capacity

Larger rotors increase braking torque because the braking force acts further from the wheel axle. They also improve heat management by increasing surface area and thermal mass.

Modern bicycle rotors commonly include 140mm, 160mm, 180mm, 200mm, 203mm, 220mm and 223mm sizes depending on discipline.

Rotor thickness is becoming increasingly important for downhill and full power electric bike systems. Thicker rotors can absorb and manage more heat before temperatures spike.

Why Brakes Fade

Preparing new pads for consistent braking

Follow the bedding in instructions for your specific pads and brake system. Correct preparation helps establish contact between the pad and rotor and develop an even transfer layer.

In our initial conditioning tests, we observed green fade in fresh compounds, followed by braking power building with heat in subsequent runs. Fresh resin bound compounds can release gases as residual ingredients heat up and the material undergoes further curing. This can temporarily reduce friction.

These findings describe the tested compounds and configurations. Use the recommended bedding in procedure for your pads rather than treating a graph temperature as a universal target.

When changing compounds, follow the pad and rotor manufacturer’s cleaning and preparation instructions. Check rotor compatibility and condition before fitting the new pads.

Explore our testing and compound recommendations or visit our installation and maintenance guide.

How electric bikes change braking demands

Modern electric mountain bikes and heavy electric bikes place far greater demands on brakes than traditional bikes. More weight, higher average speeds and longer descents all increase heat entering the braking system.

This is why modern heavy duty brakes are moving towards:

• Larger brake pads
• Thicker rotors
• Higher fluid volume
• Stiffer calipers
• High temperature compounds

Shop dedicated electric bike Brake Pads for high load braking systems.

Road and Gravel Hydraulic Brakes

Road and gravel systems use the same hydraulic principles as MTB brakes but prioritise different characteristics such as weight, control and high speed consistency.

Gravel riders often need smooth predictable control on loose surfaces, while road riders require confidence under heavy braking from high speed.

Explore: Gravel Bike Brake Pads and Road Bike Brake Pads.

Choosing the right Gorilla Brakes compound

Match the pad shape to your caliper first, then choose a compound for your riding, conditions and braking load. Check the product specification and your rotor’s permitted pad compounds.

Enduro Pro compounds

Enduro Pro combines braking performance with longer pad life. For demanding electric bike use, heavy cargo and electric cargo bikes, family transport, delivery riding, loaded touring and prolonged alpine descents, start with Enduro Pro Ultimate or Enduro Pro Semi-Metallic.

Factory Racing compounds

Choose your preferred balance of bite, modulation and feel. Enduro Pro is our recommendation when braking performance and longer pad life are the priority.

Performance compounds

Everyday choices for commuters and riders of conventional bicycles. This range is not rated for electric bikes. For an electric bike or heavy cargo bike, choose an appropriately rated Enduro Pro option.

Aluminium backing plates also offer a lighter option where available. Choose the correct fitment for your brake.

Compare all 11 compounds and explore our dyno graphs · Find the right brake pads for your bike

Browse the full Gorilla Brakes Brake Pad Collection.

Final Thoughts

Hydraulic disc brakes are simple in principle but extremely detailed in practice. The hydraulic system applies clamping force. Friction between the pads and rotor produces braking torque. The complete setup determines braking performance and control.

The best brake setup is not just the most powerful one, it is the one that gives consistent friction, stable temperature behaviour, predictable lever feel and reliable performance in the conditions you actually ride.

Whether you ride MTB, downhill, enduro, electric bike, gravel, road or commute every day, choosing the correct brake pad compound helps your braking system work at its best.