The Shimano BR-R9170 [paid link] hydraulic disc brakes are widely appreciated for their exceptional stopping power and smooth performance. However, even the best systems can sometimes feel less responsive or spongy. A spongy brake feel can compromise your riding experience, leading to reduced confidence and efficiency while riding. This issue typically stems from air in the brake lines, improper hydraulic setup, or misaligned components. In this guide, we’ll break down the common causes of spongy brakes on the Shimano BR-R9170 [paid link] and provide solutions to get your brakes feeling sharp and responsive again.

Common Causes of Spongy Shimano BR-R9170 Disc Brakes

1. Air in the Hydraulic Lines

The most frequent cause of spongy brakes in hydraulic systems is air trapped in the brake lines. Air pockets within the brake lines compress when you apply the brakes, leading to a softer, less responsive feel at the lever. This issue can arise from improper bleeding, a puncture in the brake hose, or simply from extended use without a recent bleed.

2. Incorrect Brake Fluid Level

Low brake fluid can also cause sponginess in hydraulic disc brakes. When the fluid level [paid link] drops below a certain point, the system may not have enough hydraulic pressure to engage the brake pads fully, leading to reduced braking power and a soft lever feel. This issue often arises from leaks or wear over time.

3. Faulty Brake Pads

If your brake pads have become excessively worn, they may fail to make proper contact with the rotor, leading to a spongy or weak braking performance. In addition to the pad condition, the alignment of the pads within the caliper is also critical for optimal performance. Misalignment can lead to uneven braking and a spongy feel.

4. Misadjusted Brake Lever

Sometimes, the issue lies not within the brake components but with the brake lever itself. If the lever is incorrectly adjusted, it can lead to a longer pull before the brakes engage, which can be interpreted as a spongy feel.

How to Instantly Improve Your Shimano BR-R9170 Disc Brakes

Step 1: Bleed the Brakes

One of the first things to check is whether air has infiltrated the hydraulic lines. To solve this, you’ll need to bleed the brakes using Shimano’s recommended process. Here’s how to do it:

1. Gather Necessary Tools: You’ll need a Shimano Bleed Kit [paid link], brake fluid (Shimano Mineral Oil [paid link]), a 7mm wrench, and a clean rag.
2. Prepare Your Bike: Secure the bike in a stand, and ensure the brake lever is level [paid link] with the ground. Remove the brake pads and the rotor for safety.
3. Connect the Syringe: Attach the syringe filled with brake fluid to the bleed port on the brake caliper. The other syringe will go onto the brake lever bleed port.
4. Open the Bleed Port: Slowly open the bleed valve and begin to push fluid through the system. Watch for any air bubbles to escape, which is a sign that air is being flushed out.
5. Close the Valve and Test: Once the fluid runs clear, close the valve and reassemble the brake components. Test the lever feel. If it feels firm, you’ve successfully bled the brakes.

Step 2: Check the Brake Fluid Level

Ensure that your Shimano BR-R9170 [paid link] brake system has an adequate amount of brake fluid. Low fluid levels can be a simple cause of spongy brakes, and topping off the fluid is an easy fix. Always use Shimano Mineral Oil [paid link] as the recommended fluid, as using the wrong type could damage the system.

1. Inspect the Fluid Reservoir: Open the brake lever’s fluid reservoir cap and check the fluid level [paid link]. If it’s below the minimum line, top it off.
2. Reassemble and Test: After topping up the fluid, close the cap and test the brake lever to ensure the brakes feel firm.

Step 3: Inspect and Replace Brake Pads

Worn brake pads can cause a spongy feeling due to insufficient contact with the rotor. Check the condition of the pads to ensure they still have sufficient material left. If the pads are worn down to the wear indicators or if the surface is uneven, it’s time to replace them.

1. Remove the Pads: Use a 5mm Allen key to remove the brake caliper and remove the old pads.
2. Install New Pads: Slide in the new brake pads, ensuring they are positioned correctly in the caliper. Make sure the pads make even contact with the rotor when the brake lever is pulled.
3. Check Alignment: Once the new pads are installed, check the alignment of the brake caliper to ensure the pads are centered on the rotor. Misalignment can lead to uneven pad wear and a spongy feel.

Step 4: Adjust the Brake Lever

If the lever travel seems too long or inconsistent, the brake lever may need adjustment. Shimano BR-R9170 brakes have an adjustable reach feature that allows you to change the position of the lever to suit your preference.

1. Adjust the Reach: Use a 2.5mm Allen key to turn the reach adjust screw. Turning it clockwise will bring the lever closer to the handlebars, while turning it counterclockwise will push the lever further out.
2. Test the Lever Feel: After adjusting the lever, test the braking performance to ensure that the lever feels firm and the brakes engage without excessive lever pull.

Step 5: Perform Regular Maintenance

Even after addressing the immediate issues, regular maintenance is essential to keep your Shimano BR-R9170 disc brakes performing at their best. Periodic checks of the brake fluid level, brake pad condition, and hydraulic performance will ensure that your system remains in top shape.

1. Inspect Brake Fluid Levels: Regularly check the brake fluid to ensure it remains at the correct level.
2. Clean the Brake Calipers and Pads: Clean the brake calipers and pads regularly to remove dirt and debris that can affect braking performance.
3. Check for Leaks: Routinely check all hydraulic connections for any signs of leakage, as even small leaks can reduce braking performance.

Conclusion

A spongy brake feel on your Shimano BR-R9170 disc brakes can be caused by several factors, including air in the hydraulic lines, low fluid levels, worn brake pads, or misadjusted levers. By carefully following the steps outlined above, you can quickly restore your brakes to their optimal performance. Regular maintenance and periodic checks will ensure that your Shimano BR-R9170 disc brakes remain responsive, providing you with maximum stopping power every time you ride.