Shimano GRX brakes are highly regarded for their performance and reliability, especially in gravel and adventure riding. However, brake squealing can be an annoying issue that cyclists often face. Understanding the causes of this common problem can help you fix it quickly, ensuring a smooth, quiet ride. In this blog post, we’ll explore the main reasons why your Shimano GRX brakes might be squealing and what you can do to fix them. 

There’s a common misconception about brake noise and squeal. It’s normal for hard compounds, such as sintered and some metallic brake pads, to make noise when wet or cold. This typically lasts only a few seconds until the pads heat up, after which the noise should stop. Squealing, however, can be caused by a variety of issues, including vibrations, air in the hydraulic system, contamination, bent or scratched rotors, uneven brake mount alignment, or sticking pistons, to name a few. No Manufacture makes a brake pads that squeals. Lets start with the most common issues. 

1. Contaminated Brake Pads or Rotors

One of the most common causes of squealing disc brakes is contamination. Brake pads and rotors are sensitive to oils, dirt, or any type of grease. When foreign substances land on the braking surface, they create unwanted noise during braking.

Causes of contamination include:

• Oil from the chain or hydraulic brake fluid leaks.
• Dirt or grime picked up from gravel or wet roads.
• Fingerprints or grease from handling the rotor or pads.

How to fix it:

• Remove the wheel and clean the brake rotor with isopropyl alcohol or a dedicated disc brake cleaner.
• Inspect the brake pads. If they appear glazed or oily, you might need to replace them.
• Try to avoid touching the rotor and pads directly with your hands during maintenance.

2. Improper Bedding-In of Brake Pads

New Shimano GRX brakes, or freshly replaced brake pads, need a proper bedding-in process to ensure optimal braking performance and reduce the chances of vibration and squealing. The bedding-in process involves heating up the brake pads and rotor to create a smooth braking surface, which also helps eliminate noise.

How to bed-in your brakes:

• Find a safe, open space.
• Ride at a moderate speed (around 15-20 mph) and gently apply the brakes until you come to a near stop.
• Repeat this process 10-15 times, gradually increasing the braking pressure with each cycle.
• Avoid coming to a complete stop during the bedding-in process, as this can cause uneven pad wear.

3. Moisture or Humidity

Water and humidity are notorious for causing brake squealing. When water gets between the rotor and pads, it can create a temporary squealing noise, especially during wet rides or when crossing through water.

How to fix it:

• Lightly apply the brakes while riding to heat up the rotors and dry off any moisture.
• If you often ride in wet conditions, consider switching to brake pads designed for wet weather, such as Gorilla Brakes’ Kevlar Resin Disc Brake Pads with heat management, which perform well in damp environments.

4. Worn or Glazed Brake Pads

Over time, brake pads can wear down, become glazed, or develop a shiny surface from overheating. This can lead to a lack of braking power and cause the brakes to squeal.

How to fix it:

• Inspect the brake pads for wear. Shimano GRX brakes often come with resin or semi-metallic pads, which tend to wear faster in harsh conditions.
• If the pads are glazed or worn down, replace them with high-quality pads like Gorilla Brakes Enduro Pro Compound, which offers excellent stopping power and noise reduction.

5. Rotor Misalignment

If your rotor is slightly misaligned, it can cause uneven contact between the rotor and brake pads, leading to squealing. Even a small warp in the rotor can result in an annoying noise.

How to fix it:

• Spin your wheel to check if the rotor is rubbing against the pads.
• If the rotor appears to be misaligned, use a rotor truing tool to gently bend it back into shape.
• Ensure that the caliper is properly aligned with the rotor by loosening the mounting bolts, squeezing the brake lever, and then tightening the bolts while holding the lever.

6. Brake Pad Material

The type of brake pad material you're using can also contribute to brake noise. Shimano GRX brakes often come with resin pads, which are quieter but can wear quickly, especially in wet or gritty conditions. Semi-metallic or metallic pads may offer better durability but can sometimes be noisier when cold or Wet.

How to fix it:

• If you're using metallic pads and experiencing excessive noise, try switching to softer compound but be aware this can also mask an underlying problem which will only get worse.

7. Improper Brake Adjustment Alignment. 

Finally, improper brake adjustment can cause squealing. If the calipers or pads aren't positioned correctly, it can lead to uneven pad wear and noise.

How to fix it:

• Check the caliper alignment to ensure it is centered over the rotor.
• Make sure the brake lever has sufficient travel and that the pads aren’t dragging on the rotor when not engaged.
• Adjust the brake lever position and pad spacing if necessary.

Watch this video to learn how to lubricate and align brake calipers and pistons.

The same principle applies to all brakes, regardless of the manufacturer or whether they are 2-piston or 4-piston brakes.

A common but often overlooked issue with Shimano GRX brakes

is cracked pistons, corrosion around the pistons, or leaking seals. While these problems can be difficult to spot at first, they can occur over time. If you've tried all the other troubleshooting steps and the issue persists, it’s essential to fully inspect the brake system for signs of these hidden problems. Replace your GRX calipers 

Conclusion

Squealing brakes can be a frustrating experience, but the good news is that most causes are relatively easy to fix. By regularly maintaining your Shimano GRX brakes, cleaning the rotors, and using high-quality brake pads like Gorilla Brakes Quiet Disc Brake Pads, you can enjoy a smooth, quiet, and powerful braking experience.

If you've tried these steps and your brakes are still making noise, it might be time to contact us for help or consider upgrading your brake pads to a more advanced compound designed to reduce noise and improve performance. Bleed Kits 

Looking to silence those squeals once and for all? Check out our Brake pads  for Shimano GRX and experience the difference in your next ride!

If you need more help please feel free to talk to us direct 01524 297 046