How to Tell if Your Rear Brake Drums Are Bad

Rear brake drums are likely bad if you feel a low-speed brake pedal pulsation, hear scraping or squealing noises from the rear, notice longer stopping distances or a soft/low pedal, smell a burning odor after driving, or find the parking brake requires excessive travel or fails to hold. In more detail, “bad” can mean the drums are worn beyond their maximum diameter, out-of-round, cracked, heat-spotted, heavily grooved, or severely rust-pitted, often accompanied by worn shoes or weak hardware.

What “Bad” Means for a Brake Drum

A serviceable drum has a smooth, round friction surface within the manufacturer’s diameter specification and works with properly adjusted shoes and intact hardware. A “bad” drum is one that is:
– Worn past the stamped maximum inside diameter,
– Out-of-round enough to cause pulsation,
– Heat-damaged (blue spots or hard spots),
– Cracked or severely grooved,
– Rusted or pitted where the shoes contact,
– Tapered or bell-mouthed from uneven wear.

Symptoms While Driving

These are the most common signs drivers notice when rear drum brakes are failing or out of spec.

• Pulsation at the brake pedal, especially at low speeds (often out-of-round drums).
• Grinding, scraping, chirping, or continuous squeal from the rear when braking (scored drums or worn shoes).
• Soft, low, or spongy pedal; pedal that sinks further than usual (excessive wear, poor adjustment, or fluid issues).
• Parking brake needs many clicks to hold—or won’t hold on a hill (worn drums/shoes or misadjustment).
• Rear-end shudder, vibration, or pulling during stops (uneven friction or a failed component on one side).
• Hot or burning smell after normal driving (dragging brakes/overheating).
• ABS/ESC light coupled with braking issues (contamination or sensor/tone-ring problems on some drum hubs).

Any combination of these symptoms warrants inspection; pulsation and persistent noise are the most common red flags.

Quick Driveway Checks Without Removing Drums

If you can’t immediately remove the drums, a few simple checks can help confirm a problem before heading to a shop.

1. Road test at 25–35 mph and brake gently to moderately: note pedal pulsation, rear noise, or a shudder.
2. Parking brake test on a safe, level area: apply the parking brake while moving slowly—rear-only braking should be smooth, not chattery or noisy.
3. After a short drive with several stops, carefully feel near (not on) each rear wheel or use an infrared thermometer: one side much hotter suggests dragging or uneven braking.
4. Lift the rear safely, release the parking brake, spin each wheel by hand: excessive drag or scraping indicates internal issues or misadjustment.

These checks won’t measure wear, but they can distinguish a rear brake problem from front brake or suspension issues.

Hands-On Inspection With Drums Removed

Safety and Preparation

Work on a flat surface, chock the front wheels, use jack stands, and keep the parking brake released. Loosen lug nuts before lifting, and torque them to spec when reinstalling.

Gather the right tools before you begin to streamline the process and avoid damage.

• Lug wrench, floor jack, and jack stands.
• Brake spring pliers and hold-down tool, flat screwdriver/pick.
• Penetrating oil; rubber mallet; anti-seize (sparingly on hub face, never on friction surfaces).
• Drum micrometer (preferred) to measure inside diameter; a dial indicator for runout if available.
• Brake cleaner, rags, safety glasses, mask (avoid inhaling dust).

Having proper measuring tools is key: internal diameter must be measured accurately to compare with the drum’s stamped limit.

Removal Tips

Most drums slide off once the wheel is removed. If the drum sticks, back off the star-wheel adjuster through the backing plate access slot and remove any retaining screws. Lightly tap around the drum’s face to break rust at the hub. On some vehicles, the drum is integrated with the hub/bearing; follow torque procedures if removing the axle/hub nut.

Do not pry against the backing plate or bend it; avoid hammering the friction surface. If the drum won’t clear a ridge, further retract the shoes before pulling harder.

What to Look For on the Drum

Examine the friction surface and the part’s identification markings to decide if reuse, machining, or replacement is appropriate.

• Maximum diameter: The drum is stamped with “MAX DIA” (e.g., 201.0 mm or 9.06 in). If the measured inside diameter exceeds this, replace the drum.
• Out-of-round/runout: Excessive variation (often >0.15–0.20 mm or >0.006–0.008 in) causes pedal pulsation; correct by machining if within spec, or replace.
• Cracks or heat checking: Any cracks, especially from the edge inward, require replacement. Blue/purple hot spots indicate hard spots and potential recurring pulsation.
• Deep grooves and lips: Heavy scoring or a pronounced ridge suggests significant wear; if machining to clean up would exceed max diameter, replace.
• Rust pitting or flaking: Pitting in the shoe contact area reduces friction consistency; moderate to severe pitting typically calls for replacement.
• Taper/bell-mouth: Uneven wear across the width (wider at one edge) points to adjustment or hardware issues; machining may not fully correct if near limits.

Remember: drums are wear-limit parts. If you’re close to the maximum diameter even before machining, replacement is the safer option.

What to Look For on Shoes and Hardware

Drum performance is inseparable from the condition of the shoes, springs, and hydraulic components.

• Shoe lining thickness: Replace if the thinnest point is near or below about 2–3 mm; check both leading and trailing shoes.
• Glazing or contamination: Shiny, rock-hard linings or oil/brake fluid-soaked shoes reduce friction and should be replaced.
• Uneven wear: One shoe much more worn indicates a seized adjuster, sticky backing plate contact points, or a weak/failed return spring.
• Hardware fatigue: Stretched or corroded return springs and tired hold-downs cause drag and poor release—replace as a kit.
• Wheel cylinders: Peel back dust boots; any wetness or corrosion suggests leakage—replace or rebuild and bleed the system.
• Adjuster mechanism: Ensure the star wheel turns freely; clean and lubricate threads with high-temperature brake lubricant.

When drums are serviced, replacing shoes and hardware as a set on both sides helps restore balance and prevents early recurrence.

Measure and Decide: Resurface or Replace?

Use a drum micrometer to measure internal diameter at multiple points. Compare to the stamped “MAX DIA.” Check runout/out-of-round with a dial indicator if possible.

Use these practical decision points:

• Over max diameter or cracked: Replace—do not machine.
• Within spec but out-of-round or scored: Machine if cleanup will keep the drum under max diameter; otherwise replace.
• Heat-spotted/hard spots: Replacement is usually better; machining may not eliminate pulsation.
• Light glazing with good thickness: A light, proper cut or replacement; many shops now replace due to cost parity and better results.

Because new drums are often inexpensive, replacement is increasingly favored over machining unless the drums are newer and well within spec.

Causes and Prevention

Understanding why drums go bad helps you prevent a repeat failure after repairs.

• Chronic drag from misadjustment or seized hardware—clean, lube contact points and adjusters; ensure proper shoe orientation.
• Overheating from heavy loads or riding the brakes—downshift on descents and avoid constant light brake application.
• Wheel cylinder leaks—replace leaking cylinders and flush old brake fluid (every ~2–3 years is common guidance).
• Corrosion—periodic inspections and cleaning in rust-belt climates reduce pitting and sticking.
• Improper torque on wheels/hubs—use a torque wrench to minimize distortion.

Routine maintenance—especially hardware renewal and correct adjustment—extends drum and shoe life and keeps braking consistent.

Costs and Time

Budgeting helps you choose between machining and replacement and plan for related parts.

• Rear drums: about $30–$150 each, depending on vehicle and quality.
• Shoe set: about $20–$80; hardware kit: $10–$25; wheel cylinders: $10–$40 each.
• Labor: typically 1.0–2.0 hours per rear axle; shop rates vary widely (often $100–$200+/hr).
• Machining: $10–$20 per drum where offered, but less common as new drums are often cost-effective.

Replacing drums, shoes, and hardware together often delivers the best value and reduces repeat labor.

After Repair: Bedding and Checks

Proper break-in is critical for smooth, quiet operation and full braking power.

1. Bed the shoes: perform 8–10 moderate stops from ~30–40 mph to seat the linings, allowing cooling between stops.
2. Recheck parking brake travel and adjust if needed; ensure the wheels spin freely when released.
3. Verify no fluid leaks, no abnormal heat, and torque lug nuts to spec after 25–50 miles.

Bedding creates an even transfer layer on the drum surface and stabilizes friction, minimizing noise and pulsation.

When to See a Professional

If you find cracks, can’t retract the adjuster, have integrated hub/bearing drums, or don’t have the right measuring tools, a professional inspection is prudent. Brake work is safety-critical; unresolved pulsation, leaks, or overheating should be addressed immediately.

Summary

Bad rear brake drums reveal themselves through pedal pulsation, rear-brake noises, weak parking brake performance, and signs of overheating. A definitive assessment requires removing the drums, checking for cracks, grooves, heat spots, rust pitting, out-of-round, and measuring internal diameter against the stamped maximum. Replace drums that are cracked or beyond spec; machine only if cleanup keeps them within limits. Refresh shoes and hardware in pairs, address leaks, and bed the brakes after service to restore smooth, reliable stopping.

How to tell if rear drum brakes are bad?

You can tell rear drum brakes are bad by noticing symptoms like scraping or grinding noises, a spongy or low brake pedal, a shaky or pulling vehicle, and a weak parking brake. A professional mechanic can definitively check the thickness of the brake shoe linings and inspect the inside of the brake drum for scoring or cracks to confirm any issues.
 
This video demonstrates how to visually inspect drum brakes and identifies potential issues: 54sSupercheap AutoYouTube · Mar 8, 2010
Symptoms of Bad Rear Drum Brakes

• Unusual Noises: Listen for scraping, grinding, or screeching sounds when you press the brake pedal. This can happen when the metal backing of a worn brake shoe starts to dig into the drum. 
• Altered Brake Pedal Feel: A soft, spongy, or low brake pedal can indicate wear, especially if the pedal goes closer to the floor than usual. 
• Vehicle Pulling or Shaking: If the vehicle pulls to one side when braking, it could mean uneven wear or a problem with one of the drum brakes. 
• Weak or Loose Parking Brake: A parking brake that doesn’t hold the car securely on an incline, or requires excessive force, is a sign of worn-out drum brake components. 
• Brake Pedal Vibration: A pulsing sensation in the brake pedal during braking can occur if the drums are out-of-round. 

How to Confirm Drum Brake Problems
To be certain about the condition of your drum brakes, you should have a professional inspect them. This involves: 

1. Removing the Drum: A mechanic will remove the wheels and brake drums to get a closer look. 
2. Inspecting the Brake Shoe Lining: They will check the thickness of the lining. If it’s too thin or covered in oil or grease, the shoes need to be replaced. 
3. Examining the Drum Surface: The inside surface of the drum will be inspected for deep grooves, scores, or other signs of wear. 
4. Checking for Fluid Leaks: Leaks from the wheel cylinder (which can be seen after pulling back the rubber boot) can indicate a faulty component that needs replacement. 

When to Seek Professional Help
While some signs are obvious, a definitive diagnosis requires professional inspection. If you notice any of the above symptoms, it’s best to have your vehicle checked by a mechanic to ensure your safety and prevent more costly repairs.

What does a drum brake diagnosis start with?

A drum brake diagnosis starts with understanding the symptoms reported by the vehicle’s driver, which can include strange noises, a soft or pulsating brake pedal, pulling to one side, or a loose parking brake. After gathering this information, the technician then proceeds to perform a complete visual and mechanical inspection of the brake drums, shoes, springs, hardware, and wheel cylinders to find the root cause of the problem. 
Gathering Information from the Driver 

• Listen to the Symptoms: The driver’s description of the problem is the crucial first step. 
• Ask Detailed Questions: Inquire about:
  • Noises: Squealing, grinding, or scraping sounds when braking. 
  • Pedal Feel: Soft, spongy, or pulsating brake pedal, or a pedal that feels too hard. 
  • Vehicle Behavior: Car pulling to one side when braking or vibrating. 
  • Parking Brake: Issues with the parking brake holding the vehicle, or the pedal/lever feeling too easy to set. 
• Document the Concerns: Accurately note the symptoms and when they started to help pinpoint the problem. 

Performing a Complete Inspection 

• Inspect the Drums: Opens in new tabCheck for signs of wear, deep grooves, cracks, or excessive surface diameter that would require replacement or machining. 
• Check the Brake Shoes: Opens in new tabExamine the brake shoes for lining wear and ensure they are within the acceptable thickness. 
• Examine Hardware and Springs: Opens in new tabInspect the springs, clips, and other hardware for damage, excessive wear, or corrosion that could affect adjustment. 
• Check Wheel Cylinders: Opens in new tabInspect the wheel cylinders for signs of leakage or other damage. 
• Test the System: Opens in new tabEvaluate the brake pedal feel and function after the initial inspection to correlate with the reported symptoms. 

What do bad rear drum brakes sound like?

Scraping or Grinding Noise
When the brake shoe friction material is worn to the point that the metal brake shoe backing contacts the drum, a scraping/grinding noise will be heard each time the brakes are applied.

How do I know I need new brake drums?

You can tell drum brakes are bad if you hear grinding, scraping, or squealing noises when braking, feel a low, soft, or pulsating brake pedal, or notice the vehicle pulling to one side or the parking brake feels loose or doesn’t hold. You may also experience a general loss of braking effectiveness or a vibrating sensation through the brake pedal when you stop. 
Auditory Signs

• Grinding or Scraping: Metal-on-metal sounds when you press the brake pedal often mean the brake lining has worn off, and the metal backing plate is contacting the brake drum. 
• Squealing: A high-pitched squeal can indicate worn-out brake pads, but it can also be a symptom of dirty or unevenly worn brake drums. 

Pedal and Driving Feel 

• Low or Soft Brake Pedal: Opens in new tabA low pedal can be caused by a loss of brake fluid or worn brake shoes, which create more clearance between the shoe and the drum, reducing stopping power. 
• Pulsating or Vibrating Pedal: Opens in new tabIf the brake pedal shudders or vibrates when you stop, it could mean the brake drums have become warped or are out-of-round. 
• Vehicle Pulling: Opens in new tabThe car pulling to one side when you brake can indicate uneven pressure or wear in the drum brake system. 
• Loose or Weak Parking Brake: Opens in new tabA parking brake that doesn’t hold the vehicle firmly in place can be a sign that the drums or shoes are excessively worn. 

Visual and Other Checks

• Visible Scoring on Drums: Opens in new tabIf you remove the drum to inspect it, look for deep grooves or pitting on the drum’s surface. 
• Worn Brake Shoes: Opens in new tabCheck the thickness of the brake shoe lining; if it’s very thin or worn down to the metal, the shoes need to be replaced. 
• Leaking Fluid: Opens in new tabLook for brake fluid leaks around the wheel cylinder, which would be a clear sign of a problem within the drum assembly.