How to Diagnose and Fix Noisy or Squealing Shimano SM-RT70 Disc Brakes

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When your Shimano SM-RT70 [paid link] disc brakes start to make noise, it can be both frustrating and concerning. Whether you’re a seasoned cyclist or just getting into road biking, understanding how to diagnose and fix noisy or squealing disc brakes is crucial for maintaining optimal braking performance and ensuring a smooth ride. In this guide, we’ll explore the common causes of brake noise and provide step-by-step instructions for fixing the issue.

Understanding the Causes of Noise in Shimano SM-RT70 Disc Brakes

Before diving into the steps to fix the noise, it’s important to understand why your Shimano SM-RT70 [paid link] disc brakes might be making noise. There are several common factors that contribute to squealing or noisy brakes:

1. Contamination on the Brake Pads or Rotor

Contamination is the most common cause of noise in disc brakes. Brake pads or rotors can easily pick up oils, dirt, or debris from the road, which leads to squeaking or squealing sounds when braking. Contamination reduces the friction between the brake pad and rotor, which negatively impacts braking performance.

2. Worn or Misaligned Brake Pads

If the brake pads are worn down too much, they may start to make noise as they scrape against the rotor. Additionally, if the pads aren’t properly aligned, they might cause uneven contact with the rotor, resulting in noise.

3. Rotor Warping or Damage

If your Shimano SM-RT70 [paid link] rotors are warped, bent, or damaged, they can create uneven friction, leading to squealing noises. Warping can occur from excessive heat, heavy braking, or impact with debris or obstacles.

4. Improper Brake Pad Bedding-In

When new brake pads are installed, they need to undergo a bedding-in process to ensure even pad-to-rotor contact. If the bedding process wasn’t completed properly, the brake pads may make noise as they fail to fully contact the rotor surface.

5. Environmental Factors

Environmental factors such as rain, mud, or extreme heat can also contribute to noisy brakes. Moisture can cause pads to become temporarily less effective, resulting in squealing during initial braking. Similarly, hot weather can affect the brake pads’ composition, causing them to make more noise.

Diagnosing the Source of the Noise

To resolve the issue, first, you need to determine what’s causing the noise. Here’s how to go about it:

Step 1: Check for Contamination

  • Inspect the brake pads and rotor for any visible signs of contamination like oil, grease, or dirt. If contamination is present, it’s essential to clean both the rotor and the brake pads thoroughly.
  • To clean the rotor, use a disc brake cleaner and a clean rag to wipe down the surface. Avoid using regular household cleaners as they can leave residues that interfere with braking.
  • For contaminated brake pads, use sandpaper to gently roughen the pad surface. This will help eliminate contamination and restore friction.

Step 2: Inspect the Brake Pads

  • Check the thickness of the brake pads. If the pads are worn down to less than 1mm in thickness, they need to be replaced immediately.
  • Also, make sure the brake pads are aligned properly. Misalignment can lead to uneven pad wear and cause squealing noises.

Step 3: Check for Rotor Warping

  • To check for warped rotors, spin the wheel and visually inspect the rotor. If it wobbles or doesn’t spin smoothly, it might be warped. You can also use a rotor truing tool to check for any significant bends.
  • If the rotor is only slightly warped, you can try to true it by gently bending it back into shape using a rotor truing tool. If the warping is severe, however, replacement is the best option.

Step 4: Check the Bedding-In Process

  • If the brake pads are new and haven’t undergone a proper bedding-in process, perform a few controlled stops to properly bed the pads. This involves gradually increasing braking pressure over several rides to ensure full pad-to-rotor contact.

Fixing the Noisy Shimano SM-RT70 Disc Brakes

Once you’ve identified the source of the noise, follow these steps to fix the issue.

1. Cleaning the Pads and Rotor

If contamination is the issue, follow these steps:

  • Remove the wheel from the bike to gain full access to the disc rotor and brake pads.
  • Use a clean rag and disc brake cleaner to wipe down the rotor. Make sure to clean both sides of the rotor thoroughly.
  • If the brake pads are contaminated, remove them from the brake caliper and lightly sand the pad surface to remove the contamination. Be gentle to avoid reducing the pad material too much.

2. Replacing Worn Brake Pads

If the brake pads are worn beyond the recommended thickness, it’s essential to replace them with new Shimano SM-RT70-compatible pads. Here’s how:

  • Remove the wheel and brake caliper to gain access to the brake pads.
  • Use a 5mm Allen wrench [paid link] to remove the bolts holding the brake pads in place.
  • Slide the old brake pads out of the caliper and insert the new ones, ensuring they are properly aligned.
  • Reassemble the brake caliper, ensuring that the brake pads sit correctly against the rotor.

3. Truing the Rotor

If your rotor is warped, here’s how you can attempt to true it:

  • Install the rotor back onto the wheel and place the wheel back into the frame.
  • Use a rotor truing tool to gently bend the rotor back into shape. If the rotor has a severe bend, you may need to replace it entirely.

4. Performing a Proper Bedding-In Process

If the brake pads are new, it’s important to go through the bedding-in process. Follow these steps:

  • On a safe, flat area, accelerate to about 15-20 mph.
  • Apply gentle braking pressure to slow the bike down to a stop. Do not come to a complete stop. Allow the brakes to cool between stops.
  • Repeat the process 10-15 times, gradually increasing braking force to ensure proper pad-to-rotor contact.

Preventing Future Noise

To avoid future noisy or squealing Shimano SM-RT70 disc brakes, follow these maintenance tips:

  • Regularly clean the rotors and pads to remove any debris or contamination.
  • Ensure that your brake pads are properly aligned and not excessively worn.
  • Inspect your rotors for warping and true them regularly if necessary.
  • Perform the bedding-in process for new brake pads to ensure optimal braking performance.

By staying proactive with maintenance and making sure your brakes are properly set up, you can prevent noise and ensure your Shimano SM-RT70 disc brakes function smoothly for many rides to come.