Disc Brake - Noise/Causes and Solutions

Bulletin: G91-006

Section: General

Dated: 7/25/91

Applicable to: USA, Canada

SUBJECT:
DISC BRAKE NOISE

Included in this Service Bulletin is a fact sheet which outlines the causes and possible solutions for disc brake noise.

Those in direct customer contact, such as Service Advisors and Service Managers, should carefully read and understand the information so that they can more clearly advise owners with complaints of brake noise.

The fact sheet is RRNA's policy statement on the subject and accurately describes the situation as it currently exists.

Occasional or persistent high-pitched noise from disc brakes is not unusual. This condition is present in many vehicle makes from all over the world.

Safety First

Four-wheel disc brakes have been standard on the Range Rover since 1970. The Range Rover ABS brake system is one of the most advanced, and sophisticated in the world today. The capacity of the brake system is much greater than most American owners will ever use. In one of the factory performance tests, a Range Rover must descend one of the highest, steepest mountain roads in Europe towing a 7,700 pound trailer. The brakes are designed to recover quickly from deep water and mud crossings as well as perform at the high speeds driven in other markets. There is no compromise in this robust, state-of-the-art system.

The Real Cause of Brake "Squeal"

"Brake Squeal" tends to be more common in high-performance vehicles, where the braking capacity substantially exceeds the amount of stopping power used by the driver. Four-wheel disc brakes provide superior performance, but also compound the situation. The high-swept areas are designed to stop a fully loaded vehicle traveling at high speeds in reasonable distances with minimal fade. If a Range Rover were equipped with a lighter-duty brake system the brakes would never squeal, but brake performance would be compromised.

When the brakes are applied lightly, the brake pads are not pressed firmly against the brake rotor. This allows a vibration to develop and a noise is produced. Routine, light brake applications have a compound effect in that the pad and rotor surfaces become "glazed" and the propensity to vibrate is increased. Additionally, the asbestos-free brake pads used in the Range Rover tend to be more squeak-prone.

Drivers Make The Difference

Different drivers of the same vehicle can have different experiences with brake noise. One who uses the brakes lightly is more likely to have brake noise, and one who uses the brakes firmly will not. Likewise, vehicles which carry heavier loads or pull trailers are less likely to exhibit brake squeal because a greater portion of the system capacity is used to stop the vehicle.

No Magic Cures

There is no "cure" for brake squeal. Replacing parts, "deglazing", "chamfering" or lubricating contact surfaces may work temporarily.

The Solution

There are two ways to solve this complaint:

- A. Help the driver understand what is causing the noise and encourage him/her to use the brakes more firmly to prevent the noise.

- B. Reduce the performance of the brake system through softer pads or pad "treatments" which effectively reduce the brake system capacity. The driver will be forced to use greater percentage of the brake capacity.

CAUTION:
Solution B is not recommended! Turning a high-performance brake system into a marginal brake system is wrong, and risky. There is no treatment or alternate brake pad approved by Land Rover Engineers for the Range Rover.

Be Understanding

Be sure to understand the customers concerns about brake noise. Develop a diplomatic technique for helping the customer to understand what is causing the noise and that the only cure is a slight modification of driving habits to more closely match the vehicles's potential.

Using The Brakes Is Good, If They Are Used Properly

Heavier pedal application will not wear the brakes faster. On the contrary, light and frequent use of the brakes will shorten pad life considerably and create brake squeal.

Other, Unusual Noises

Of course, any unusual brake noises should be taken seriously. This could indicate worn pads which require servicing.

A continuous scraping noise could indicate that a small stone or some debris is caught in the brake caliper. This is easily cured by applying the brakes in reverse a few times.

A vehicle which is parked even for a few days in humid conditions can develop surface corrosion on the brake rotors, which will create a "grinding" noise when the vehicle is first used again.

Keeping the brake calipers clean by flushing the area with water when washing the vehicle can reduce accumulations of material which could contribute to some brake noise.