How to Fix Weak Brake Feel with Shimano BR-RS405 Disc Brake Pad Alignment

Posted on
in No category

When it comes to maintaining the braking performance of your Shimano BR-RS405 [paid link] disc brakes, one crucial aspect that often gets overlooked is the alignment of the brake pads. Misaligned pads can result in weak braking performance, compromised stopping power, and an overall uncomfortable riding experience. In this guide, we’ll walk you through why your brake pads might feel weak and how to properly align them to restore optimal braking performance.

Why Brake Pad Alignment Matters

Brake pad alignment is essential because it ensures that the pads are positioned correctly against the rotor, providing consistent and even contact for optimal braking. When the pads are misaligned, they may not fully engage the rotor surface, leading to a reduction in braking power and a spongy brake feel. This can also cause uneven pad wear, increased noise, and vibrations during braking.

Proper alignment also prevents the pads from rubbing against the rotor unnecessarily, which can lead to overheating, reduced performance, and quicker wear. In the case of Shimano BR-RS405 [paid link] disc brakes, achieving the right alignment is key to getting the best performance out of your bike.

Tools and Materials Needed

Before we dive into the steps for aligning the Shimano BR-RS405 [paid link] disc brake pads, make sure you have the following tools on hand:

Tools Required:

  • 5mm Allen wrench [paid link]
  • Torque wrench [paid link]
  • Small flathead screwdriver
  • Brake pad spacer or a piece of cardboard
  • Brake fluid (if needed)
  • Cleaning supplies (optional)
  • Isopropyl alcohol (for cleaning)

Step-by-Step Guide to Aligning Shimano BR-RS405 Disc Brake Pads

1. Prepare the Bike and Remove the Wheel

  • To begin, make sure your bike is stable. If you have a bike stand [paid link], this will be the most efficient option.
  • Remove the wheel from the bike to give you access to the brake rotor. It’s important to check the rotor for any warping or damage before proceeding with pad alignment.

2. Install a Brake Pad Spacer

  • Insert a brake pad spacer into the caliper. This will ensure the pads don’t accidentally close while you are working on the alignment. If you don’t have a specific brake pad spacer, you can use a piece of cardboard or a similar non-abrasive material.

3. Loosen the Caliper Mounting Bolts

  • Using a 5mm Allen wrench [paid link], slightly loosen the two caliper mounting bolts. This will allow you to adjust the caliper’s position in relation to the rotor. It’s important to only loosen the bolts enough so that the caliper can move freely but not too much that the caliper detaches completely.

4. Align the Caliper with the Rotor

  • With the mounting bolts loosened, manually align the brake caliper so that the pads sit evenly on either side of the rotor. The rotor should be centered between the pads with equal spacing on both sides. You can gently squeeze the brake lever to help center the caliper.
  • Check the position from both the front and rear to ensure the pads align properly without touching the rotor.

5. Tighten the Caliper Mounting Bolts

  • Once the caliper is centered, carefully tighten the mounting bolts using a torque wrench [paid link]. Shimano recommends tightening these bolts to a specific torque setting to avoid over-tightening or under-tightening. Refer to the specifications for your Shimano BR-RS405 brakes for the exact torque value (typically around 6-8 Nm).
  • Tighten the bolts evenly, alternating between each bolt to ensure the caliper remains centered throughout the process.

6. Check for Proper Pad Alignment

  • Once the caliper is securely mounted, remove the brake pad spacer. Spin the wheel and gently apply the brakes to check if the pads are making even contact with the rotor. There should be no rubbing, and the braking feel should be firm and consistent.
  • If the pads are still rubbing, you may need to make slight adjustments by loosening the caliper bolts again and re-centering the caliper.

7. Adjust the Brake Pads (If Necessary)

  • If you’re experiencing weak braking even after adjusting the caliper, the issue could be with the pads themselves. Check if the pads are worn unevenly or if they have hardened due to excessive heat. In such cases, replacing the brake pads may be necessary to restore optimal performance.

8. Reinstall the Wheel and Test

  • After completing the alignment, reinstall the wheel, ensuring the rotor fits cleanly back into the caliper. Test the brake lever to ensure the brake pads engage properly and the brake feels firm.
  • If the brake feel still seems weak, consider checking the hydraulic brake system (if applicable) for air in the lines or potential fluid issues.

Troubleshooting Weak Brake Feel After Alignment

Even after aligning the brake pads correctly, there are a few common issues that can contribute to weak braking performance with the Shimano BR-RS405:

  • Air in the Brake Lines: If you’re using hydraulic brakes, air trapped in the brake lines can cause sponginess in the brake lever. If the brake feels spongy after alignment, consider performing a brake bleed to remove any air from the system.
  • Worn Brake Pads: Brake pads that are worn down to their minimum thickness will reduce stopping power. Ensure the pads are still within their serviceable life and replace them when necessary.
  • Rotor Issues: Warped rotors can also contribute to weak braking. Check the rotor for any visible signs of damage or warping. If the rotor is out of true, it may need to be straightened or replaced.
  • Contaminated Pads or Rotor: Oil, dirt, or other contaminants on the brake pads or rotor can drastically reduce braking power. Clean the rotor with isopropyl alcohol and check for contamination on the pads. If needed, clean or replace the pads.

Final Thoughts

Proper brake pad alignment is crucial to maintaining the performance of your Shimano BR-RS405 disc brakes. Regular checks and adjustments can help ensure that your bike continues to provide reliable stopping power when you need it most. If after following this guide you are still experiencing issues, it may be worth consulting a professional bike mechanic to check for more complex problems.