Why Are My Bike Brakes Squealing? 7 Causes and How to Fix Them
The Dreaded Brake Squeal
Nothing ruins a ride like screaming brakes. Whether it's an embarrassing squeal on the trail or a grinding noise that makes everyone look, brake noise is annoying and often signals a problem. Here's how to diagnose and fix the most common causes of squealing disc brakes.
1. Contaminated Brake Pads or Rotors
The most common cause of brake squeal.
Symptoms
- Sudden onset of squealing after working fine
- Reduced braking power
- Glazed, shiny appearance on pad surface
Causes
- Chain lube overspray
- Oily fingerprints on pads or rotors
- Brake fluid leak
- Riding through puddles with oil/fuel
The Fix
- Remove pads and sand the braking surface with fine sandpaper (400 grit)
- Clean rotors thoroughly with isopropyl alcohol and a clean rag
- If contamination is severe: Replace pads entirely - contaminated pads often can't be fully cleaned
- Prevent future contamination: Apply chain lube with the wheel removed or use a shield
2. New Brake Pads Not Bedded In
New pads need proper break-in to work quietly.
Symptoms
- Squealing immediately after installing new pads
- Inconsistent braking power
- Pulsing or grabbing sensation
The Fix
Proper bedding-in procedure:
- Find a safe, flat area
- Accelerate to moderate speed (15-20 km/h)
- Apply brakes firmly but don't lock up
- Release before stopping completely
- Repeat 20-30 times
- Let brakes cool for 5 minutes
- Repeat the cycle once more
This transfers a thin layer of pad material to the rotor, creating a matched braking surface.
3. Glazed Brake Pads
Overheated pads develop a hard, glassy surface.
Symptoms
- Squealing after long descents
- Shiny, glass-like pad surface
- Significantly reduced braking power
- Burning smell after hard braking
Causes
- Dragging brakes on long descents
- Using brakes that are too small for your weight/terrain
- Organic pads on demanding descents
The Fix
- Light glazing: Sand pad surface with 400 grit sandpaper, re-bed
- Severe glazing: Replace pads with gravity or sintered compounds that resist glazing
- Prevent future glazing: Upgrade to larger rotors or more powerful brakes
4. Misaligned Brake Caliper
Caliper not centered over the rotor causes uneven pad contact.
Symptoms
- Squealing that starts after wheel removal/installation
- Rubbing sound even when not braking
- Uneven pad wear (one side thinner than other)
The Fix
- Loosen caliper mounting bolts
- Squeeze brake lever to center caliper on rotor
- While holding lever, tighten bolts evenly
- Release lever and spin wheel to check for rubbing
- Fine-tune by slightly loosening one bolt and adjusting
5. Warped or Bent Rotor
A rotor that's not perfectly flat causes intermittent contact.
Symptoms
- Rhythmic pulsing squeal (once per wheel rotation)
- Visible wobble when spinning wheel
- Rubbing at specific points only
Causes
- Crash damage
- Over-tightening rotor bolts
- Extreme heat then rapid cooling
- Transporting bike with rotors pressed against something
The Fix
- Minor warp: Use a rotor truing tool or adjustable wrench to carefully bend back
- Severe warp: Replace the rotor
- Prevention: Use a rotor protector during transport
6. Worn Brake Pads
Pads worn to the metal backing plate.
Symptoms
- Metal-on-metal grinding sound
- Severely reduced braking power
- Visible metal where pad material should be
- Damaged rotor surface (scoring)
The Fix
Replace pads immediately. If you've been running metal-on-metal, inspect your rotors for damage - you may need to replace them too.
Use our Brake Finder to find the exact pads for your brakes.
7. Wet Brakes
Water between pad and rotor causes temporary squealing.
Symptoms
- Squealing only in wet conditions
- Noise goes away after a few brake applications
- Normal braking power once warmed up
The Fix
This is normal! A few brake applications will clear the water. If wet-weather squealing is excessive, consider switching to gravity brake pads which handle moisture better.
When to Replace vs. Repair
| Symptom | Try Fixing | Replace Pads |
|---|---|---|
| Contamination | Light contamination | Heavy/oil contamination |
| Glazing | Surface glazing | Deep glazing, loss of power |
| Wear | - | Under 1mm pad material |
| Noise after bed-in | Re-bed procedure | If noise persists |
Prevent Future Brake Noise
- Keep brakes clean: Wipe rotors with isopropyl alcohol regularly
- Be careful with lube: Apply chain lube away from brakes
- Don't touch: Handle pads by edges only, never touch braking surface
- Proper bedding: Always bed in new pads correctly
- Right compound: Use sintered pads for wet conditions
Still Having Problems?
If you've tried everything and your brakes still squeal, it might be time for fresh pads. Find the right pads for your brakes or contact us - we're happy to help troubleshoot.