The Shimano BR-R7170 [paid link] hydraulic disc brakes are a popular choice for cyclists looking for high-performance braking systems. However, like any hydraulic brake, they may sometimes exhibit a spongy feel, which can negatively impact your braking performance and overall riding experience. A spongy brake lever can be caused by several factors, from air in the brake lines to issues with brake pad wear or lever adjustment. This guide will help you identify the cause of the sponginess and provide solutions to restore optimal performance to your Shimano BR-R7170 [paid link] disc brakes.

Understanding the Cause of Spongy Brakes

A spongy brake lever is a common issue that can occur with hydraulic disc brakes. In the case of the Shimano BR-R7170 [paid link] model, there are a few key factors that could contribute to this sensation:

1. Air in the Brake System

The most common cause of a spongy brake feel is air trapped in the hydraulic brake lines. Air bubbles prevent the fluid from being properly transmitted, making it harder to generate adequate braking force when you pull the lever. This can make the brake feel soft or spongy.

2. Low or Contaminated Brake Fluid

Hydraulic brake systems rely on high-quality brake fluid to transmit force. If the fluid level [paid link] is low, or the fluid has been contaminated with dirt or moisture, the brakes may feel spongy. Over time, brake fluid can degrade or become contaminated, leading to poor performance.

3. Brake Pad Issues

Worn-out or improperly aligned brake pads can also cause a spongy brake lever. If the pads are too worn or unevenly worn, they may not make proper contact with the rotor, leading to reduced braking power and a spongy feel.

4. Lever and Caliper Adjustment

Incorrect lever or caliper adjustments can also affect the feel of your brakes. If the brake lever reaches the handlebar with minimal pressure, it can indicate that the caliper or lever position is not properly adjusted, which can result in a soft brake feel.

How to Improve the Spongy Feel in Your Shimano BR-R7170 Disc Brakes

To restore your Shimano BR-R7170 brakes to their full potential, follow these steps to diagnose and fix the spongy brake issue:

Step 1: Check the Brake Fluid

Start by inspecting the brake fluid in your Shimano BR-R7170 system. If the fluid level [paid link] is low, top it off using the appropriate Shimano mineral oil [paid link]. Additionally, if the fluid has become dirty or contaminated, it’s time to flush the system and replace the fluid.

How to Replace Brake Fluid:

• Remove the brake pads to prevent them from being contaminated with fluid.
• Attach the Shimano brake bleed kit [paid link] to the bleed port on the caliper.
• Use the syringe to extract the old fluid from the system.
• Fill the syringe with fresh Shimano mineral oil [paid link] and slowly inject it into the brake system.
• Ensure the oil fills the entire system and there are no air bubbles.
• Perform the final bleed to remove any remaining air from the system.

Step 2: Bleed the Brakes

If your brakes feel spongy, it’s likely due to air trapped in the brake lines. Bleeding the Shimano BR-R7170 hydraulic system will remove the air and restore solid brake feel.

Bleeding Procedure:

• Secure the bike in a work stand and remove the wheel to gain access to the brake caliper.
• Attach the Shimano bleed kit [paid link] to the bleed nipple on the brake caliper.
• Open the bleed valve slightly and use a syringe to force brake fluid into the caliper.
• Slowly work the syringe to push the fluid through the system, allowing the air bubbles to rise and be pushed out.
• Close the bleed valve once the fluid runs clear and bubble-free.
• Test the brake lever to ensure a firm feel and repeat if necessary.

Step 3: Inspect and Replace Brake Pads

If the brake pads are worn out or contaminated with oil, it can cause the brakes to feel spongy. Check the thickness of your pads and look for any signs of uneven wear or contamination.

Pad Replacement:

• Remove the pads from the caliper.
• Check for any wear indicators or uneven wear across the pad surface.
• If necessary, replace the pads with new Shimano-compatible brake pads.
• Install the new pads and check their alignment with the rotor to ensure they sit correctly and make full contact.

Step 4: Adjust the Brake Lever and Caliper

Ensure the brake lever and caliper are correctly aligned. The lever should not feel too soft or too firm when pulled. If it does, adjustments are necessary.

Lever Adjustment:

• Check the reach adjustment on the brake lever. This controls the distance the lever travels before it engages. Adjust it so that the lever feels comfortable when you pull it.
• If the lever feels too soft, adjust the lever travel using the tool provided by Shimano or consult the user manual.

Caliper Adjustment:

• The brake caliper should be positioned evenly relative to the rotor. If it’s misaligned, it can cause poor pad contact, leading to sponginess.
• Use a caliper alignment tool to ensure the caliper is centered over the rotor.

Step 5: Test the Brake System

Once you’ve performed the above steps, it’s important to test the brakes. Pump the lever a few times to ensure the brake feels firm and responsive. If the lever still feels spongy, repeat the bleeding process or check for any additional issues such as misalignment or fluid leaks.

When to Seek Professional Help

If the issue persists after completing the steps outlined above, there may be an underlying problem that requires professional attention. For instance, a damaged hydraulic line or a faulty master cylinder may be the cause of the spongy lever. In such cases, it’s best to consult with a professional bike mechanic to diagnose and fix the problem.

Conclusion

A spongy brake lever on your Shimano BR-R7170 hydraulic disc brakes can be frustrating, but with proper maintenance and troubleshooting, you can restore full braking performance. Ensure you regularly check the brake fluid, bleed the system when necessary, replace worn pads, and adjust the lever and caliper for optimal performance. By following these steps, you’ll be able to enjoy consistent and reliable braking on your road bike.