AfterMarketNews Auto Care Pro AutoProJobs Auto-Video.com Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service

Second-rate parts mean second-rate results

When it comes to diagnosing a problem, one of the biggest mistakes is thinking that the problem is gone after you’ve installed a new part. I’ve had vehicles brought in countless times with the same old story attached to them. The customer will say:...

Read more...

GearWrench Launches Street Team, a New Mobile Driver Program

GearWrench, a premier hand tool brand from Apex Tool Group, has announced Street Team, a new program that gives independent mobile distributors the support of an established tool brand without the restrictions of a franchise. "Response to the program...

Read more...

AUTO 7 Named Approved Vendor For Automotive Parts Associates

Steven Kruss, president of Auto 7, which supplies Korean-made, OEM-quality automotive parts to distributors across North America, announced that Auto 7 has been named an approved vendor of Automotive Parts Associates (APA), one of the nation’s...

Read more...

Internal Engine Oil Consumption Diagnostics

Due to the variables in engine design and ­operating conditions, internal engine oil ­consumption complaints are often the most difficult to solve. In some cases, oil consumption might be more severe under low-speed operation, in other cases, high-speed...

Read more...

Hyundai Fuel System, Emissions Diagnostics

Hyundai has done a good job of improving its ­offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to increase its market share year over year. If you aren’t...

Read more...

Curing Volvo Manual Transmission Rattle

In an effort to increase fuel efficiency, today’s engines produce more torque so they can be ­driven at extremely low rpm. ­Reduced viscosity engine and gearbox oils, less vehicle weight and improved aerodynamics also contribute to better fuel economy....

Read more...

Talk To All Available Modules With Autel's MaxiDiag Elite MD802

Derived from Autel’s Professional Series tool, the MaxiDAS DS708, the MaxiDiag Elite MD802 enables the user to not only get into the OE enhanced OBD II system with mode 6 access and live data graphing, but it also allows a technician to scan the...

Read more...

Reflashing & Reprogramming Tools

In the first half of 2014, NHTSA has issued more than 15 recalls where the fix was to reflash a module on a vehicle. In the same time frame, more than 100 TSBs have also been issued where the solution is to reflash a module. These recalls and TSBs...

Read more...

Pulling Codes: An Advanced Misfire Story The Story of P0301

This article will document code P0301 — Misfire Activity on Cylinder No. 1 — a code many of you have run into, but sometimes we have case studies that are worthy of mention. Our subject vehicle is a 2007 Mercury Mountaineer. The vehicle has...

Read more...

The Why, Where, When of TPMS Sensors

To understand any TPMS relearn procedure, you have to understand this: Sensors only transmit, they do not receive. No vehicle asks a sensor for information on how it is doing. I know you’re thinking a sensor does receive signals when the vehicle...

Read more...

Most Common Causes of Misfire Codes

A flashing check engine light and a P0301 to P0312 diagnostic trouble code (DTC) is a surefire indication that one or more cylinders are misfiring. Occasional misfires may pass unnoticed, but a steady misfire is hard to miss. The engine usually feels...

Read more...

Pattern Failures of MAF and MAP Sensors

Pattern failures are those failures that happen over and over again — and the same applies to how customers describe these failures. Customers might unknowingly give you the answer to their problem without needing to open the hood. In this article,...

Read more...

Home Brakes 7 Brake Myths Busted

Print Print Email Email

There are some myths about brake pads, rotors and hydraulics that need to be busted. These myths can hurt and hinder a technician’s ability to diagnose and solve some brake problems and customer concerns.

On the surface, some of these myths make sense. The logic can seem sound and explain a problem, but they do not resolve the real issues with a brake system.

A Rotor’s Minimum Thickness Specifications are Based on Heat
False: The discard or minimum thickness specification is based on travel of the caliper piston if the pads were worn to the backing plates.

If you had worn pads and a rotor below specification, there is a possibility the piston could start leaking and possibly become dislodged from the bore causing a failure of the brake system. Heat, warping and fading have nothing to do with discard specifications.  

Soft Pads and Hard Pads
False, with a pinch of engineering truth. The engineering term for measuring the hardness of brake pads is compressibility.

Engineers typically measure compressibility as a manufacturing quality control measurement and not as a performance measurement. Compressibility is an important characteristic and can influence pedal feel, but it has very little to do with noise, rotor wear and pulsation.

What the driver is experiencing is the type of friction (tribology) the friction material is using to stop a vehicle. A “hard pad” is a pad that is abrasive to the rotor. This could be classified as a semi-met pad. These types of pads can have very stable friction over a wide range of temperatures.

What a technician or customer think of as a “soft” pad is typically an organic or ceramic formulation. How these friction materials generate brake torque is by adhesion type of tribology. These friction materials leave or transfer a layer of friction material (transfer film or “seasoning”) on the rotor’s surface that some friction material companies claim can smooth out the rotor surface, thereby causing less excitation and noise at the friction coupling. Also, this transfer layer may not be as sensitive to heat induced brake torque variation. Some of these friction materials can be friendly to rotors.

Both of types of friction materials can be the same in terms of compressibility. Calling one material soft and one hard is not possible unless your shop has a $20,000 machine to measure the compressibility of the materials.

Compressibility can influence pedal feel, but only in extreme cases where the pad could be defective. What really influences pedal feel is the coefficient of friction of the brake pad.

Damaged Brake Hoses Can Cause Brakes to Drag
 False, with a dash of truth. The myth usually takes place on a vehicle where the brakes are stuck on at just one wheel. The technician tries just about every thing and eventually theorizes it is a restriction in the brake hose. 

Brake hoses can be damaged by road debris and some clamps. Stock brake hoses are typically two or three layers. All modern hoses have a stiff internal liner that is in contact with the fluid. The outer layers are typically a softer material designed to absorb impacts with road debris.
 
The myth typically states that the inner liner was damaged and created a flap or check valve in the line. This check valve prevents the pressure from releasing at the caliper. But, this has been know to happen older brake lines from the 1960s.

In theory, it does makes sense, but you have to ignore some facts. First, if this flap was created, it would not form a internalized flap. Chances are the entire liner would fail and the brake fluid would be up against the softer outer liner. This would make the hose bulge and eventually burst. 

Chances are the restriction could be  a stuck emergency brake, caliper slides or even a problem with the metering/combination valve. Also, many stuck brake problems are related to brake booster or meter/combination valve problems.

Wet Brake Rotors Increase Stopping Distances
 False: Remember when you were first learning to drive and some adult told you to tap the brake pedal after you drove through a puddle? In the days of drum brakes, this was good advice, but with disc brakes this piece of advice does not hold water.

If a vehicle is moving, water is thrown off the face of the rotor by centrifugal force. Any water on the pads is inconsequential.

Replacement Brake Pads are Regulated by the Government
False: There are no government regulations concerning brake pad performance.  

 

 

Brake Pads Need to Warm Up
 False: Street brake pads are designed to produce even brake torque even at very low temperatures. This is even true for exotic carbon ceramic brake systems on street-driven vehicles.

The exception for this myth is high performance racing pads that require some heat in the friction material to generate its highest coefficient of friction. Manufacturers of these pads will say that these pads should only be used for off-highway purposes.

Brake Pads Are The Source of All Brake Noise
 True & False: All brake pads do produce vibrations when they are applied. This happens on all brake systems. But, it is how the vibrations are transferred to the rest of the vehicle that will cause a driver to hear or not hear the noise. A brake pad is merely the a string on a guitar, it is up to the player or vehicle to decide how it sounds.

Humans have a limited range of hearing so the sound made by some brake pads might be unheard.

What can cause noise is a change of the friction material due to heat. A “consistent” friction material causes less vibrational excitation variation at the friction coupling by having consistent brake torque at environmental extremes of humidity and temperature (-40F to 500F).

Typically, high frequency noises come from the caliper, rotor or bracket. Low frequency noises, like growls, grunts and moans, can be caused by struts, knuckles or even the body structure.

The option for technicians are to isolate the pads with lubricants, shims and restoring the hardware to like-new condition. 

The following two tabs change content below.

Andrew Markel

Andrew Markel is an ASE Certified Technician and former service writer, and he brings this practical knowledge to the Brake & Front End team as editor.
Latest articles from our other sites:

Beck/Arnley Launches TRUE|Friction Brake Pad Series

Beck/Arnley has launched a new brake pad series that using the same type of material recommended by the vehicle’s manufacturer. TRUE|Friction pads are specifically designed to match the most current...More

TRW's Premium Chassis Program Tops 3,000 Mark

TRW’s North American (NA) Aftermarket Group has extended its all makes premium chassis program by an addition 527 SKUs. The total number of SKUs available from TRW now exceeds 3,000. Mark Thorpe,...More

Internal Engine Oil Consumption Diagnostics

Due to the variables in engine design and ­operating conditions, internal engine oil ­consumption complaints are often the most difficult to solve. In some cases, oil consumption might be more severe...More

Hyundai Fuel System, Emissions Diagnostics

Hyundai has done a good job of improving its ­offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to...More

Ernst Offers Socket Boss Universal Twist Lock Socket Tray

Versatility is a must for organizing any socket set. Capitalize on maximum configuration possibilities with the new Universal Twist-Lock Socket Tray from Ernst. Individual rails can be removed or switched...More

Ranger Introduces New Automatic Leverless Tire Changer

Ranger Products, a division of BendPak Inc., is bringing another new tire changer to market. Its latest R80DTXF tire changer features an automatic bead lifter, variable speed turntable and bilateral bead...More

Hyundai: Engine Oil Pump Replacement Guidelines During Engine Replacement

Applicable Vehicles: All models Follow the guidelines outlined in this bulletin to install a new oil pump after an internal engine repair or engine short block replacement. Note: A new or remanufactured...More

The Why, Where, When of TPMS Sensors

To understand any TPMS relearn procedure, you have to understand this: Sensors only transmit, they do not receive. No vehicle asks a sensor for information on how it is doing. I know you’re thinking...More