SM-RT70 Disc Brake Pad Alignment: Why It Feels Weak and How to Fix It

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The Shimano SM-RT70 [paid link] disc brake rotor is a high-performance component designed to deliver reliable stopping power under various conditions. However, even the best brakes can sometimes underperform due to issues with disc brake pad alignment. If your SM-RT70 [paid link] brakes feel weak, the problem could lie in the alignment of the brake pads. Proper pad alignment ensures the pads engage the rotor correctly, maximizing braking force and performance. In this guide, we will explain the causes of poor brake pad alignment, how to diagnose this issue, and the steps to correct it, ensuring your SM-RT70 [paid link] disc brakes perform at their best.

Why Poor Brake Pad Alignment Affects Braking Power

Brake pad alignment is crucial because it directly impacts how effectively the brake pads contact the rotor. When the pads are misaligned, they may not fully engage with the rotor, resulting in inconsistent braking power. Misalignment can cause several issues, including:

  • Reduced Stopping Power: If the pads are not aligned properly with the rotor, they may only make partial contact, which leads to weaker braking performance.
  • Uneven Pad Wear: Misalignment causes the pads to wear unevenly, potentially leading to premature wear on one side of the pad while the other side remains relatively untouched.
  • Increased Noise: Misaligned pads can also cause squealing or grinding noises due to the inconsistent contact with the rotor.
  • Heat Build-up: Inconsistent pad contact may create excessive heat in certain areas of the rotor, leading to potential overheating and reduced performance.

How to Diagnose Misaligned Brake Pads

Before adjusting the brake pads on your SM-RT70, you’ll need to determine if they are indeed misaligned. Here’s how you can check:

  1. Visual Inspection:
    • Look at the brake pads through the caliper to see if both pads are aligned symmetrically on either side of the rotor.
    • Check the gap between the pads and the rotor. It should be even across the entire rotor’s surface.
    • If one side of the pad is closer to the rotor than the other, this is a clear sign of misalignment.
  2. Spin the Wheel:
    • Spin the wheel slowly by hand and observe the rotor. If you notice any wobbling or an uneven gap between the rotor and the pads, this could indicate the pads are misaligned.
    • Listen for any unusual sounds, such as rubbing or squeaking, which can also be a sign of misalignment.
  3. Brake Test:
    • Perform a quick test by applying the brakes while the bike is stationary or in motion. If the braking feels weak or inconsistent, this further suggests an alignment issue.

How to Fix Misaligned Brake Pads on Shimano SM-RT70 Disc Brakes

Correcting misaligned brake pads on your Shimano SM-RT70 disc brakes is a relatively straightforward process. Follow these steps to realign the pads and restore optimal performance.

Tools Required

  • 5mm Allen wrench [paid link]
  • Brake pad spacer (optional)
  • Shimano brake fluid (for hydraulic models)
  • A clean rag or cloth

Step 1: Remove the Wheel

  • Start by removing the wheel to gain easy access to the brake caliper and rotor.
  • If necessary, use a quick-release lever or axle wrench to remove the wheel.

Step 2: Loosen the Brake Caliper Mounting Bolts

  • Use the 5mm Allen wrench [paid link] to slightly loosen the two caliper mounting bolts, but do not fully remove them.
  • Loosening these bolts will allow the caliper to move slightly, helping you align the brake pads.

Step 3: Adjust the Brake Pads

  • Gently tap the caliper while applying the brake lever, forcing the brake pads into correct alignment with the rotor.
  • Once the pads are properly aligned, tighten the caliper mounting bolts securely, ensuring the pads remain in place.
  • If the brake pads are not properly centered, you may need to manually adjust them by moving the caliper slightly to one side.

Step 4: Check Rotor Trueness

  • With the pads properly aligned, check the rotor for trueness. Spin the wheel again to see if the rotor is straight.
  • If the rotor is bent, it can cause the pads to misalign repeatedly. A rotor truing tool may be needed to straighten the rotor.

Step 5: Reinstall the Wheel

  • Once the brake pads are aligned, and the caliper is tightened, reinstall the wheel and make sure the rotor is centered within the caliper.

Step 6: Test the Brakes

  • After reassembling everything, perform a brake test to ensure the pads are engaging correctly.
  • Test both front and rear brakes by applying them firmly to ensure proper stopping power.
  • If the brake lever feels spongy or if there is any weak braking performance, you may need to bleed the brakes or adjust the pad spacing again.

Preventing Brake Pad Misalignment on Shimano SM-RT70

Regular maintenance and proper installation can help prevent future brake pad alignment issues. Here are some tips to ensure long-term performance:

  • Check Pad Alignment Regularly: During routine maintenance, check the alignment of your brake pads to ensure they remain in the proper position. This can help avoid performance issues before they become noticeable.
  • Avoid Over-tightening Caliper Mounting Bolts: When reinstalling the caliper, be cautious not to overtighten the mounting bolts, as this could force the caliper out of alignment. Tighten them just enough to hold the caliper securely.
  • Keep the Rotor Clean: Dirt and debris on the rotor can cause the pads to misalign or wear unevenly. Clean the rotor regularly with a rag and brake cleaner to keep it in optimal condition.
  • Upgrade to High-Quality Pads: Low-quality brake pads can wear unevenly and lead to alignment issues. Consider using high-quality pads designed for the SM-RT70 to ensure consistent performance and even wear.

Conclusion

Proper brake pad alignment is crucial for maximizing the stopping power and longevity of your Shimano SM-RT70 disc brakes. Misaligned pads can cause weak braking, increased noise, and uneven wear, which can degrade your overall cycling experience. By following the steps outlined above, you can quickly identify and correct any pad alignment issues. Regular maintenance and attention to detail will ensure your Shimano SM-RT70 disc brakes continue to deliver reliable, powerful performance for years to come.