Mechanics

Scraping

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Car Moving: This section includes symptoms that present themselves when the car is in motion

Loose Brake Caliper: The brake calipers are designed to slow the vehicle when applied. The brake caliper holds these brake pads that are applied to the brake rotor. If the caliper is lose because the main caliper mounting bolt(s) are missing it will allow the caliper to ride against the inside of the rim producing a scraping noise. To check for this condition inspect the brake caliper mounting bolts to make sure they are tight and intact. If these mounting bolts are missing replace and tighten with new. Do not drive the vehicle in this condition, brake operation failure can occur.

Worn Out Brake Pads or Shoes: The brake pads on your car are designed to slow the vehicle when applied. If the brake pads are completely worn out they will can create a scraping noise when the brakes are applied. This scraping noise is created when the pad is forced against the brake rotor in normal braking operation. To check for this condition inspect the brake pads in question. The brake pads should have composite material between the pad backing plate and the brake rotor, or on the rear of the vehicle brake drum and shoes. If a brake grinding noise is allowed to continue, brake operation failure could occur. The rotor featured below is a perfect example of what can happen if a brake scraping noise is left unattended.

Scraped Brake Rotor
Scraped Brake Rotor

When a scraping brake rotor is neglected, it will cause the brake system to fail due to the separation of the rotor hat (center) from the outer web (braking surface). Additional problems can occur include the brake pad to fall out completely or the brake caliper to blow out a piston. Either condition will cause brake operation failure. Do not drive the vehicle in this condition, brake operation failure will occur.

Relocate Brake Rotor Heat-Dust Shield: When the brake rotor is in operation it produces heat and the rotor is subject the road side dust that can inhibit proper brake function. To help protect the brake rotor a shield is fastened to the spindle. If this shield becomes slightly out of alignment it can come in contact with the rotating brake rotor creating a scraping noise. To check for this condition support the car to remove the wheel in question. Next, rotate the brake rotor by hand to recreate the sound. Then inspect the air gap between the brake rotor and shield, reposition as needed and reassemble.

Checking Axle Bearing Failure: An axle bearing is designed to support the weight of the vehicle while allowing the wheels to rotate. These bearings are manufactured with high grade steel that resists wear under extreme conditions. When an axle bearing fails it allows metal to contact metal under pressure with a linear motion creating a scraping noise. Once an axle bearing fails it cannot be repaired, replacement is required. Remove axle bearing and replace with new and recheck. Some vehicles are equipped with a bearing hub assembly. The bearing below is the style of bearing is replaced by un-bolting the bearing hub assembly and replacing it with new.

Axle Bearing Hub
Axle Bearing Hub

Other bearing designs include separated bearings that include inner and outer bearings with bearing races, a four piece set. Separated bearings require an inboard seal attached to the bearing hub. This seal rides on the spindle to hold grease inside of the bearing hub, keeping lubrication inside of the bearings.

Axle Bearing/Race Set with Seals
Axle Bearing/Race Set with Seals

Check for Tire to Body Contact: The tires on your car are designed to rotate with a minimum clearance between the body and the wheel. If this clearance is minimized by the wrong tire size or suspension modification or failure it can allow the tire to rub against the inner fender wheel which will create a scraping noise. To check for this condition inspect the clearance between the tire and inner fender well. Check the suspension for spring failure or tire size to make sure the proper tires have been installed.

If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Also, gain manufacturer specific instructions and information by clicking - Auto Repair Manual

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-08-16)