Brake Pads vs. Rotors: How to Tell Which One Is the Problem

If you hear squealing under light braking, see thin pads (about 3 mm or less), or get grinding, it’s likely your brake pads; if you feel a pulsing brake pedal or the steering wheel shakes during moderate-to-hard stops at speed, your rotors are the likely culprit. In practice, listening for specific noises, noting how the pedal and steering feel when braking, and doing a quick visual check of pad thickness and rotor surface will usually tell you which part needs attention.

What Each Part Does—and Why It Matters

Brake pads are the friction material that clamp onto the rotors to slow the car. Rotors are the discs the pads squeeze. Pads wear out by design, and rotors wear more slowly but can become uneven, grooved, heat-checked, or too thin. Distinguishing pad wear from rotor issues saves time and ensures you replace the right parts.

What Sounds Tell You

Different noises point to different causes. Use these clues to separate pad-related issues from rotor problems.

• High-pitched squeal at low speed or light braking: Often the pad wear indicator touching the rotor—pads near end of life.
• Intermittent light squeal that stops when you brake harder: Could be pad glazing, dust, or missing/dirty shims—usually pad/hardware related.
• Metallic grinding or scraping when braking (or sometimes even rolling): Pads likely worn down to the metal backing plate or debris caught—stop driving and inspect; rotors may already be damaged.
• Rhythmic “shhh-shhh” that speeds up with vehicle speed: Could be a high spot or light rotor contact, backing plate rub, or minor runout—often rotor-related.

While noise isn’t definitive by itself, squeal tends to point to pads; grinding indicates severe pad wear (and rotor damage); rhythm that tracks wheel speed can implicate a rotor irregularity.

What You Feel Under Braking

Feel is one of the clearest ways to spot rotor issues versus pad wear.

• Pulsation in the brake pedal that increases with speed: Typically rotor thickness variation (DTV) or runout, not “warped” rotors in the classic sense.
• Steering wheel shake during highway-speed stops: Usually front rotors with runout/DTV.
• Vibration felt in the seat or rear of the car when braking: Often rear rotors or drums.
• Car pulls to one side under braking: Uneven pad wear, sticking caliper slide/piston, or contaminated pad/rotor on one side.
• Soft/spongy pedal or pedal slowly sinking: Hydraulic issue (air, leak, old fluid), not pads/rotors.

In short, pulsation and shaking point to rotors; directional pull and uneven bite often point to pad or caliper issues; a soft pedal is typically hydraulic.

Visual Inspection: Quick Checks You Can Do

If it’s safe to do so, a visual check can confirm what you’re hearing and feeling. You can often inspect without removing the wheel; for a thorough check, remove it.

1. Look through the wheel or caliper window: Estimate pad friction thickness. If it’s around 3 mm or less (about the thickness of two credit cards), replace pads soon.
2. Compare inner vs. outer pads: A big difference (more than ~1 mm) suggests sticky slide pins or a caliper issue—address before pad-only replacement.
3. Inspect the rotor face: Deep grooves you can catch a fingernail in, heavy scoring, blue/purple heat spots, cracks, or flaking rust indicate rotor service/replacement.
4. Check the outer edge “lip”: A pronounced lip suggests significant rotor wear—measure thickness to see if it’s above the minimum.
5. Find the minimum thickness: Most rotors have “MIN TH” cast or stamped on the hat. If your measurement is at or below this spec, replace the rotor.

If pads are thin or uneven and rotors are smooth and within spec, pads may be all you need; damaged, thin, or heat-spotted rotors should be resurfaced (if possible) or replaced.

Driveway Tests (No Wheel Removal Needed)

These simple tests can help pinpoint the problem before you wrench.

• 60 to 20 mph moderate stop on a straight, empty road: A pulsing pedal or shaking wheel points to rotor issues.
• Low-speed light braking in a parking lot: A consistent high-pitch squeal suggests pad wear indicators; grinding points to pads gone and rotor contact.
• Hands lightly on the wheel during braking: Pull to one side hints at pad/caliper problems, not rotor thickness alone.
• Note ABS behavior: A rapid buzz in the pedal only during hard stops on slick surfaces is normal ABS activation, not rotor pulsation.

Combine feel, sound, and behavior to narrow your diagnosis before opening anything up.

What to Measure (Typical Numbers)

Measurements confirm what you suspect. You’ll need a ruler or caliper for pad thickness and a micrometer/dial indicator for rotors.

• Pad thickness: New is often ~10–12 mm; plan replacement at ~3 mm or sooner if performance/noise issues appear.
• Rotor thickness: Must be above the “MIN TH” stamped on the rotor; never machine below that spec.
• Rotor runout (wobble): Typical max 0.002–0.004 in (0.05–0.10 mm).
• Rotor thickness variation (DTV): Usually must be under ~0.0006 in (0.015 mm).

Always check the service manual or the rotor hat for exact specifications for your vehicle.

Common Scenarios and Likely Causes

Match your symptoms to these patterns to decide whether it’s pads, rotors, or something else.

• Squeal at light brake, pads ~3 mm: Pads due; rotors likely okay if smooth and within spec.
• Grinding when braking, visible grooves: Pads worn out, rotors damaged—replace pads and rotors.
• Pulsing pedal, shake at highway speeds, rotor lip present: Rotors have runout/DTV—replace or resurface; inspect pads for uneven wear.
• Pull to one side, inner pad thinner than outer: Caliper slide/piston issue—fix hardware/caliper and replace pads (rotors if damaged).
• Spongy pedal, no noise, long travel: Hydraulic issue (air/old fluid/leak)—bleed or repair; pads/rotors may be fine.
• Vehicle sits often (hybrid/EV), rusty rotor faces with squeal: Surface rust/glaze—may clear with a few firm stops; persistent pitting needs rotor service.

If multiple symptoms occur (e.g., pulsation plus grinding), address both pads and rotors and inspect calipers and hardware.

Replace Pads, Rotors, or Both?

Deciding what to replace comes down to wear, condition, and specs.

• Pads only: Acceptable if rotors are smooth, above minimum thickness, and within runout/DTV spec—light resurfacing may help with bedding.
• Pads and rotors: Recommended if rotors are thin, scored, heat-spotted, or out of spec; also common due to low rotor cost and better results.
• Always replace in axle pairs: Both fronts or both rears together for even braking.
• Hardware and fluid: Replace pad hardware/shims, clean/grease slide pins, and consider a brake fluid flush if fluid is 2–3+ years old or pedal feel is soft.
• Bed-in new pads/rotors: 5–8 moderate stops from ~40 to 10 mph with cool-down between; avoid holding the pedal hard at a stop immediately after bedding.

Proper installation, clean hub faces, and correct lug torque are critical—uneven lug torque can induce rotor runout and cause new-parts pulsation.

Safety and Practical Tips

Brakes are safety-critical. Work carefully or consult a professional if you’re unsure.

• Use jack stands on a level surface; never rely on a jack alone.
• Clean rust from hub faces; check caliper slides and boots; torque lugs to spec in a star pattern.
• If a rotor is cracked, severely grooved, or below spec, replace it—do not machine below minimum.
• If you experience sudden grinding or a strong pull, minimize driving and inspect immediately.

A careful inspection and proper installation prevent repeat problems, uneven wear, and braking instability.

Costs and Expectations

Costs vary by vehicle and quality of parts. As a rough guide (parts only, typical passenger cars): pads $40–$150 per axle; rotors $60–$200 each; hardware $10–$25; brake fluid $10–$25. Labor at shops varies widely; professional pad-and-rotor service per axle commonly ranges from a few hundred dollars to over $800 on premium or performance vehicles.

Summary

Squeal and thin pads point to pad replacement; grinding means pads are gone and rotors are likely damaged; pedal pulsation or steering shake under braking points to rotor runout or thickness variation. Confirm by inspecting pad thickness, rotor surface, and measuring against specs. Replace parts in axle pairs, service hardware, and bed-in new components for best results. If in doubt about safety or measurements, have a qualified technician inspect the system.

How to check brake rotors?

To check brake rotors, look for visible defects like deep grooves, cracks, blue discolorations from overheating, or excessive rust, and feel for a pulsating brake pedal or vibrating steering wheel. For an accurate assessment, you’ll need to remove the wheel to inspect both faces of the rotor for even wear, check for debris in the cooling fins, and use a micrometer to measure the rotor’s thickness against the manufacturer’s minimum discard thickness.
 
Signs of a Bad Rotor

• Pulsating Brakes: A pulsation felt in the brake pedal or steering wheel when you press the brakes is a sign of uneven rotor thickness. 
• Visual Grooves or Scoring: Deep, distinct grooves or rough patches on the rotor’s surface are a clear indication of wear and tear. 
• Excessive Rust: While some surface rust is normal, deep rust that affects the rotor’s overall structure needs attention. 
• Blue Coloration: A blue or discolored tint on the rotor indicates it has been overheated, which can compromise its integrity. 
• Cracks: Any visible cracks, especially those extending to the edge of the rotor, require immediate replacement. 

How to Inspect Your Rotors

1. Remove the Wheel: You will need to remove the tire to get a clear view of the rotor’s surfaces. 
2. Visually Inspect: Examine both the inner and outer surfaces of the rotor. 
3. Check for Grooves: Run your finger across the rotor’s surface; if you feel deep grooves, it indicates wear. 
4. Check for Cracks: Look closely for any cracks or damage on the rotor’s surface or inside its cooling fins. 
5. Look for Rust: Check for excessive rust, especially on the wear surfaces. 
6. Inspect the Cooling Ducts: Make sure there is no debris lodged in the rotor’s cooling ducts. 
7. Measure Thickness: Use a micrometer to measure the rotor’s thickness. 
8. Check Minimum Thickness: Find the minimum thickness specification for your rotor, which is often stamped on the rotor itself or can be found in a repair manual, and compare it to your measurement. 
9. Measure Thickness Variation: To check for warping, take several thickness measurements at different points on the rotor and subtract the lowest from the highest. 
10. Check for Runout: A dial indicator can be used to measure the rotor’s runout, or how much it wobbles. 

If you find any significant defects, or if the rotor’s thickness is below the minimum specification, the rotor needs to be replaced.

Is it my brakes or my rotors?

Decreased Braking Performance
If your vehicle takes longer to come to a complete stop or if the brakes feel less responsive, it’s time to inspect the brake rotors. Reduced braking performance can result from worn-out or damaged rotors that need replacement.

How can you tell if your brake pads and rotors are bad?

Signs Your Brake Pads are Worn

1. Squealing when you stop. Many brake pads have squealer tabs that touch the rotor to make noise as a warning sign your pads are low.
2. Grinding when you drive and brake.
3. Extended stopping distances.
4. Grooves in the rotor surface.
5. Pulsation in the pedal.
6. Pulling to one side.

How do I know if I need new rotors or just brake pads?

You likely need new brake pads if you hear high-pitched squealing or your pedal feels soft; you likely need new rotors if you feel a pulsating or vibrating steering wheel, hear grinding, or see deep grooves, significant rust, or edges on the rotor surface. A professional inspection is recommended to accurately diagnose the issue and determine if both components need replacement. 
You can watch this video to see the difference between good and bad rotors: 59sMohawk ChevroletYouTube · Apr 7, 2023
Signs You May Need New Brake Pads

• High-pitched squeal: An annoying high-pitched noise that occurs when you apply the brakes often indicates that the brake pads are worn down and the wear indicator is making contact with the rotor. 
• Soft or spongy brake pedal: If your brake pedal feels like it travels closer to the floor or is less responsive than usual, it could be a sign of thin brake pads. 
• Visible thin pads: A quick visual inspection through your wheels may reveal that your brake pads are less than 1/4 inch thick. 

Signs You May Need New Rotors 

• Grinding or scraping noise: A low-pitched grinding or scraping sound when braking is a serious indicator that the rotors are damaged, warped, or the pads have worn down completely. 
• Pulsating or vibrating steering wheel: If you feel a vibration or pulsing in the steering wheel or brake pedal when you apply the brakes, it often means the rotors are warped. 
• Grooves, scores, or rust: A visual inspection of the rotor surface can reveal deep grooves, scoring marks, or excessive rust buildup, which can compromise braking performance. 
• Large edges: A noticeable lip or edge on the outer part of the rotor is a sign that the rotor has worn unevenly and needs replacement. 
• Vehicle pulling to one side: If your vehicle drifts to one side when you brake, it could be due to uneven rotor wear. 

This video explains how to check your brake pads and rotors: 59sBudget MechanicYouTube · Oct 11, 2022
When to Consider Replacing Both 

• Uneven pad wear: Opens in new tabIf one brake pad is worn unevenly, it can indicate a warped rotor, requiring both parts to be replaced.
• New pads on old rotors: Opens in new tabInstalling new brake pads on worn or damaged rotors can lead to improper pad wear and reduced braking performance, so it’s often best practice to replace them together.