The #1 Bicycle Mechanic Website in the World!


Cardio Trek Personal Trainer
Cardio Trek
Sports Trainer
East York, Toronto, ON
Hours: Tues-Thurs 10-5:30, Sat-Sun 10-3:30
Cardio Trek is best known for teaching archery lessons in Toronto.

Sunday, August 20, 2023

Troubleshooting Bicycle Disk Brakes

Here is a list of common issues that can occur with disc brakes on a bicycle, along with troubleshooting steps and fixes:

  1. Squeaking or squealing noise:

    • Symptoms: High-pitched noise when applying the brakes.
    • Troubleshooting:
      • Clean the brake rotor and brake pads to remove any dirt or debris that may be causing the noise.
      • Inspect the brake pads for wear. If they are worn unevenly or have become contaminated, they may need to be replaced.
    • Fix:
      • Clean the brake rotor with isopropyl alcohol or a specialized disc brake cleaner.
      • Remove the brake pads and lightly sand them with fine-grit sandpaper to remove any glazing or contamination.
      • Reinstall the brake pads and ensure they are properly aligned with the rotor.
      • Bed in the brake pads by gradually applying the brakes and progressively increasing the force until the noise diminishes.
  2. Brake lever feels spongy:

    • Symptoms: Excessive lever travel, poor braking response, lack of firmness.
    • Troubleshooting:
      • Check for air in the brake system or insufficient brake fluid.
    • Fix:
      • Start by bleeding the brake system to remove any air bubbles and ensure proper fluid circulation.
      • Follow the manufacturer's instructions or seek professional help if you are unfamiliar with the bleeding process.
      • If bleeding doesn't resolve the issue, inspect the brake hoses for leaks or damage. Replace any damaged hoses.
      • Check for proper alignment of the brake caliper and rotor, ensuring there is no interference or rubbing.
      • Adjust the brake lever reach if needed, ensuring a comfortable position for your hand.
  3. Brake pads worn out:

    • Symptoms: Reduced braking performance, longer stopping distances, visible wear on the brake pads.
    • Troubleshooting:
      • Inspect the brake pads for wear. If the pad material is worn down to the wear indicators or below, they need to be replaced.
    • Fix:
      • Remove the old brake pads.
      • Install new brake pads that are compatible with your disc brake system.
      • Ensure the brake pads are properly aligned with the rotor.
      • Follow the manufacturer's instructions for proper bedding-in of the new brake pads.
      • Test the braking performance and make further adjustments if necessary.
  4. Brake rotor contamination:

    • Symptoms: Poor braking performance, inconsistent braking, vibration or pulsation when applying the brakes.
    • Troubleshooting:
      • Check for oil, grease, or other contaminants on the brake rotor.
    • Fix:
      • Clean the brake rotor thoroughly with isopropyl alcohol or a specialized disc brake cleaner.
      • If the rotor is severely contaminated or damaged, it may need to be replaced.
      • Inspect the brake pads for contamination as well. Clean or replace them as necessary.
      • Check the brake caliper alignment and adjust if needed.
      • Bed in the brake pads to restore optimal braking performance.
  5. Sticky or seized brake caliper:

    • Symptoms: Brakes not fully releasing, uneven or inconsistent braking, excessive heat buildup.
    • Troubleshooting:
      • Observe the movement of the brake caliper when applying and releasing the brakes.
    • Fix:
      • Check for any debris, rust, or corrosion on the brake caliper and its moving parts.
      • Clean the caliper thoroughly and lubricate any necessary contact points with an appropriate lubricant.
      • Ensure the brake caliper pistons move freely and retract properly.
      • If the caliper is severely damaged or worn, it may need to be replaced.
      • Verify proper alignment of the caliper with the rotor and adjust if necessary.

If you are unsure about performing any disc brake repairs or adjustments, or if the issue persists after troubleshooting, it is highly recommended to seek assistance from a professional bicycle mechanic to ensure the brakes are properly diagnosed and repaired for safe riding.

No comments:

Post a Comment


Spam comments will not be approved. If you want to advertise your product or service (or want to sponsor this blog) please send an email.

Popular Posts

Looking for a bicycle mechanic school in Canada? The Quadra Island Bike School in British Columbia is a Canadian bicycle mechanic school that trains professional bicycle mechanics against the backdrop of the beautiful Quadra Island.

About the Author

Charles Moffat is equal parts bicycle mechanic, cyclist, painter, sculptor, fantasy writer, poet, website designer and pun maker. For more details see



Do you own a bike shop and are looking to hire a bicycle mechanic in North America? Just email me with the job posting details and I will post it for you. (Also, please let me know when the job has been filled so I can update the posting.)


If your bicycle is basically junk and you don't know what to do with it then SELL IT TO ME. I will use it for parts. I will give you a fair price ($20 to $30) for your old clunker just so I can rip it apart for parts.

If you need repairs check out my Bicycle Mechanic Services in Banbury-Don Mills.