How to Fix Disc Brake Rub on a Bicycle

Rubbing disc brakes waste energy, cause noise, and wear pads prematurely. The good news: most issues are simple to diagnose with basic tools. Follow these steps to silence your brakes and restore smooth spinning wheels.

Tools You’ll Need

• Bike stand or a way to lift the wheel off the ground
• 5 mm or 4 mm hex keys (depending on your caliper)
• T25 Torx wrench for rotor bolts (if needed)
• Clean rag and isopropyl alcohol (at least 70%)
• Thin business card or feeler gauge
• Rotor truing tool (or adjustable wrench wrapped in cloth)
• Light source to inspect pad clearance

Step 1: Confirm the Rub Source

1. Lift the wheel and spin it. Listen for scraping.
2. Watch the caliper from above. If the rotor deviates side to side, it may be bent.
3. If the noise only happens under braking, contamination may be the culprit rather than rub.

Step 2: Recentre the Caliper

1. Loosen the two caliper mounting bolts just enough that the caliper can move side to side.
2. Squeeze and hold the brake lever to align the caliper over the rotor.
3. While holding the lever, tighten both bolts evenly to the torque printed on the caliper (typically 6–8 Nm).
4. Release the lever and spin the wheel. Minor rub should disappear.

If the rub persists, use a thin card between one pad and the rotor while tightening the bolts. This forces a small additional gap on the rubbing side.

Step 3: True a Bent Rotor

1. Identify the rotor section that scrapes. It will push the pad outward as it passes.
2. Insert a rotor truing tool at the bent spot and gently bend away from the pad.
3. Work in tiny adjustments—apply light pressure, rotate the wheel, and recheck.
4. Repeat until the rotor spins without touching either pad.

Heat can warp rotors. Avoid cooling a hot rotor with water and check bolt torque regularly (6 Nm for most 6-bolt rotors, 40 Nm for Center Lock lockrings).

Step 4: Clean Pads and Rotor

• Remove the wheel and take out the brake pads.
• Wipe the rotor with isopropyl alcohol. Avoid touching the braking surface with bare fingers.
• Scuff glazed pads lightly with fine-grit sandpaper (220 grit), then wipe clean.
• Reinstall pads, ensuring spring clips sit correctly.

Step 5: Check Hub and Frame Alignment

If rubbing continues, inspect the wheel itself:

• Hub bearings: Worn bearings allow the rotor to wobble. Service or replace hubs as needed.
• Axle seating: Make sure thru-axles are tightened to spec (usually 10–12 Nm) and quick-release skewers are firm.
• Frame alignment: Rare, but dropout alignment issues can pull the caliper out of square. A bike shop can check facing.

Step 6: Bed In the Pads Again

After cleaning or replacing pads, bed them in:

1. Find a safe, flat area. Accelerate to 10–15 mph.
2. Brake firmly to walking speed (do not fully stop). Repeat 10–15 times.
3. Increase speed to 20 mph and repeat 3–5 times for powerful brakes.
4. Allow rotors to cool before storing the bike.

Preventing Future Brake Rub

• Inspect pad wear weekly if you commute daily. Replace pads when friction material reaches 1 mm.
• Torque rotor bolts and caliper bolts after travel or wheel removals.
• Keep rotors free from chain lube overspray by covering them when lubricating the chain.
• Store bikes upright; leaning heavily on one rotor can warp it over time.

When to Visit a Pro Mechanic

If you notice deep grooves in the rotor, leaking hydraulic fluid, or persistent rubbing after following these steps, schedule a professional service. Riding with damaged brakes risks safety.