When riders install new bicycle brake pads, two common complaints appear: weak braking power and brake squeal. This guide explains why both happen, uses dry braking test data to show how rotor condition affects performance, and provides a step-by-step bedding-in process to resolve the problem.
New rotor after one initial use vs. old rotor at 100 N handle force.
New rotor after one initial use vs. old rotor at maximum test handle force.
Old rotor, new unused rotor, and new rotor after one initial use.
Recommended number of controlled braking cycles for initial bedding-in.
What Is Brake Pad Bedding-In?
Brake pad bedding-in — also known as disc brake break-in — is the process of creating a stable contact condition between the bicycle brake pad and the disc brake rotor. The goal is not simply to wear the surface. More importantly, it helps the pad material and rotor surface form a consistent friction interface.
Surface High Points Are Leveled
Microscopic peaks on both the brake pad and rotor are gradually worn down, increasing the true contact area and improving friction efficiency.
A Transfer Layer Forms on the Rotor
A thin, even layer of friction material deposits onto the rotor surface. This transfer layer creates a more consistent friction interface between pad and rotor.
Friction Coefficient Stabilizes
As the interface matures, braking force becomes more predictable. Modulation improves, and noise and vibration are reduced when the process is done correctly.
Without Proper Bedding-In
Riders may experience weak initial braking, unstable brake feel, longer stopping distance, or brake noise — none of which necessarily mean the pad is defective.
Dry Braking Test: Rotor Condition vs. Deceleration
The following test measures braking deceleration at handle forces from 20 N to 160 N across three rotor conditions. The highlighted range (40 N – 100 N) represents the most practical braking force levels in everyday riding and clearly shows how rotor condition affects braking power.
| Sample | Rotor Condition | 20 N | 40 N | 60 N | 80 N | 100 N | 120 N | 140 N | 160 N |
|---|---|---|---|---|---|---|---|---|---|
| Deceleration (m/s²) | ▲ Practical Braking Range | ||||||||
| Sample 1 | Old rotor | 0.56 | 1.28 | 2.20 | 2.81 | 3.49 | 4.13 | 4.64 | 4.85 |
| Sample 2 | New unused rotor | 0.58 | 1.50 | 2.55 | 3.29 | 3.96 | 4.35 | 4.66 | 5.00 |
| Sample 3 | New rotor — after one initial use | 0.79 | 1.82 | 2.99 | 3.94 | 4.68 | 5.18 | 5.54 | 5.86 |
Unit: deceleration m/s² · Test method: dry braking · Handle force range: 20 N – 160 N
Bedding-In Improves Braking Power
The test data shows a clear ranking across all handle force levels. The new rotor after one initial use consistently delivered the highest deceleration values.
This result confirms that a properly conditioned rotor surface — through initial bedding-in — can significantly improve both braking force and braking stability. An old rotor with surface degradation or contamination may actually underperform a new rotor that has completed only one initial use cycle.
Why Does a New Rotor Sometimes Feel Weak at First?
A new rotor may look clean and smooth, but its surface is not yet optimized for braking. Three technical factors explain why initial braking power can be lower than expected.
Contact Area Not Fully Developed
Even when a brake pad and rotor look flat, their surfaces are not perfectly matched at a microscopic level. Initially, only a small portion of the pad contacts the rotor effectively, reducing friction efficiency. After several controlled braking cycles, contact area expands and braking power increases.
Transfer Layer Has Not Formed Yet
A stable transfer layer — a thin deposit of pad material on the rotor surface — is one of the most important factors in disc brake performance. Without it, riders may notice weak braking, unstable response, longer stopping distance, noise, poor modulation, or sudden changes in brake feel.
Old Rotor Surface Degradation
An old rotor may already carry a transfer layer, but it can also contain uneven wear, oxidation, old pad residue, heat spots, surface grooves, or contamination. These factors reduce the effectiveness of a new brake pad — which is why the old rotor showed the lowest deceleration in this test.
Why Bedding-In Is Critical for E-Bikes and Cargo Bikes
E-bikes and cargo bikes place significantly higher loads on the braking system than standard bicycles. For these applications, bedding-in is not a small detail — it directly affects safety, durability, and rider confidence.
How to Properly Bed-In Bicycle Brake Pads and Rotors
A simple, controlled bedding-in process can significantly improve brake performance from day one. Avoid extreme braking during the first few stops — overheating the pad surface too early may cause uneven material transfer or glazing.
Ride in a safe, open area with enough space to brake and roll to a complete stop.
Accelerate to a moderate speed (approximately 20–30 km/h for most applications).
Apply the brake with medium, controlled force. Slow the bike down without fully locking the wheel.
Repeat the braking cycle 10 to 20 times. Allow short rolling intervals between each stop to avoid excessive heat buildup.
Do not hold the brake when the rotor is hot. Release fully after each braking cycle.
Allow the brake system to cool completely after the bedding-in session before riding in demanding conditions.
Common Symptoms Before Proper Bedding-In
These symptoms do not always mean the brake pad is defective. In many cases, the system simply needs a correct bedding-in process.
Rotor Condition Matters More Than Most Riders Think
This dry braking test confirms three key results:
The old rotor had the lowest braking performance across all handle force levels.
The new unused rotor performed slightly better — but the transfer layer had not yet formed.
The new rotor after one initial use showed the highest braking force — up to 34% improvement at 100 N.
For bicycle brands, brake pad suppliers, and e-bike manufacturers, bedding-in test data helps explain product performance clearly and reduces misunderstanding during product evaluation.
Frequently Asked Questions
Need Custom Bicycle Brake Pads for
E-Bike, Cargo Bike, or MTB Applications?
We develop and manufacture bicycle brake pads for different riding conditions, including e-bike, cargo bike, mountain bike, and urban commuting applications. Our friction material development focuses on braking power, noise control, wear resistance, heat stability, and rotor compatibility.
If you are looking for an OEM or ODM bicycle brake pad manufacturer, contact us to discuss your testing requirements, material direction, and product development goals.
