Jump to content

  • Welcome to Auto Parts Forum

    Whether you are a veteran automotive parts guru or just someone looking for some quick auto parts advice, register today and start a new topic in our forum. Registration is free and you can even sign up with social network platforms such as Facebook, X, and LinkedIn. 

     

Brake Rotors: Resurface Or Replace?


Recommended Posts

I love this topic. Unfortunately, many brake rotors end up unnecessarily in the scrap pile. But I also know the reasons why, and if I’m looking to place blame, well, we only can blame ourselves. But is it bad? I’ll get into that down the page, but let me set the stage first.

Types of Rotors

Up through the mid-‘70s, the majority of all brake rotors “on the road” were hubbed rotors. What this meant is that the hub was cast into the rotor. Most cars and trucks up through that time were rear-wheel drive, and if they had disc brakes as an option, 99% of the time it was on the front only. The front wheel bearings of these cars were housed in the hub of the rotor. The rotors were very heavy and expensive to produce, and the wheel bearings were the tapered style of roller bearing that required regular cleaning, greasing, adjustment and seal replacement.

As front-wheel-drive cars grew in popularity in the mid-‘70s, so did the hubless or “hat” style of brake rotor. Hubbed rotors remained in regular use up through the mid-‘90s, but their popularity steadily declined until the hat rotor became almost the sole design choice of auto manufacturers. Hat rotors were far easier to service, with the front wheel bearings being sealed units mounted into the front steering knuckle. Hat rotors simply slid into place, and they were lighter-weight, less expensive and easier to manufacture.

It’s All About the Metal

Brake rotors get hot during braking, and they need to dissipate heat quickly. Functionally, all a brake rotor really does is absorb and dissipate heat. If a rotor gets too hot, it will cause brake fade and may easily warp, diminishing braking performance and causing severe brake vibration. The heavier the vehicle or the faster you’re going, the larger the rotors need to be, because the harder the brakes work, the more heat they produce.

So, the size of a brake rotor is proportionate to the type of braking it will be required to do. What’s a larger rotor? It’s more metal. What’s a thicker rotor? It’s more metal. And what determines how much heat can be absorbed and dissipated? The physical amount of metal. When a rotor wears, the diameter stays the same, but they get thinner, and when you resurface them, you’re removing even more material. The less metal you have, the less heat the rotor is able to absorb and dissipate.

How Brake Pads and Rotors Interact

Under normal braking, the surface of the rotor will become grooved to varying degrees based upon the pad material. This doesn’t affect the braking; because it occurs as a result of the contact between the brake pads and rotors, the surface of the two remain contoured. However, this surface is not acceptable when installing new brake pads and prevents the correct break-in of new pads, and it causes uneven pad wear and noise. “Pad slapping” is the comical term we use to describe replacing brake pads without resurfacing or replacing the rotors.

New brake pads have a break-in or “bedding” process that consists of repeated moderate braking. The purpose of the process is to bring the pads up to high temperatures in a controlled manner. When this occurs, the pad and rotor will transfer a thin layer of friction material to each other, allowing them to properly seat together. This is a very important aspect of brake service, as it ensures maximum braking and prevents brake fade, and this process only will occur correctly when new pads are mated with new or resurfaced rotors.

Turning the Rotors

We call it “turning,” because that’s the name of the machining process in which a workpiece is rotated against a fixed cutting tool. Any surface irregularities, including any grooves formed from normal service and also any rust or pitting, can be removed by turning the rotor.

In addition to surface condition, rotors often suffer from different forms of distortion. Lateral runout is the side-to-side movement of a rotor, measured with a dial indicator while rotating it by hand. Parallelism is the thickness of a rotor measured at multiple spots around the circumference for comparison. When describing this to a customer, we generally use the basic term “warped” rotor. These conditions will cause a vibration during braking, and in some cases, just driving at higher speeds.

Either one can be caused by normal wear or by incorrect mounting or installation of the rotor and wheels. Customers know what it means to have a warped rotor, and few of them care about the more technical terminology. Turning a rotor will correct these problems as well.

Turning a rotor involves a number of steps, the first of which is measuring it to determine if it still will be above the minimum thickness afterward. In most cases, the minimum thickness is cast or stamped into the rotor, but often it’s rusty and difficult to find, so we generally have to look up the specification anyhow.

Typically, when you turn a rotor, you’re going to remove a total of about .015 inches to .020 inches (15 to 20 thousandths of an inch) of material. It may be less on a really clean rotor, or more on a rusty, pitted or warped one. After measuring the thickness of the rotor and assessing the condition, you’ll know whether you have plenty of material left to turn it, or whether it’ll be too thin when you’re done.

If you determine the rotor can be turned, the next step is to remove it from the vehicle and mount it on the brake lathe. Hat rotors require a thorough cleaning and rust removal from the mounting surface to ensure they seat properly on the brake lathe. The mounting surfaces for a hubbed rotor are the wheel-bearing races, from which you can just wipe away the excess grease.

When the turning is complete and you’ve taken a final measurement to ensure the rotor is still at or above minimum thickness, the next step is to put a non-directional finish on the brake rotor, which aids in proper break-in. The most popular method is to use an angle-grinder with a cleaning disc, and it literally only takes a few seconds per side.

The final step includes washing the rotor in a mild soap-and-water solution. Though not visible, small metal particles remain on the rotor after turning, and these particles will embed themselves in the pad and prevent an effective break-in. Washing the rotor removes these particles. Hubbed rotors will require removing all the old grease, since a wheel-bearing clean and repack is a normal part of this service.

Back in the Day

There was a time when the hum of a brake lathe was almost as constant as the ticking of the clock on the shop wall. Hubbed rotors were big, heavy and expensive, and they lasted a long time, because they could be turned and reused multiple times before they were too thin to put back in service. The expectation of customers during this era was that their rotors would be “turned” during brake service. Even with the additional cost of labor, it still was far more expensive to replace them.

As the hat rotor slowly became the predominant rotor in use, many other changes were taking place in the automotive industry. Auto parts stores were opening up to meet the demands of the increasing number of cars on the road, and parts were being manufactured overseas. Price competition was high, and the more parts that were produced (hot rotors included), the less expensive they became.

At the same time, technician salaries were increasing, and suddenly, the labor cost to turn rotors was increasing. Then there was the process of turning the rotors. My intent in describing the process was to provide an indication of the amount of work involved, but any machining process requires very specific knowledge and procedure as well.

Turning a rotor is a machining process that can be done wrong as easily as it can be done right. Traditional hubbed rotors were very heavy, and as a result easier to turn because the weight inherently reduced vibration, and mounting them on the lathe was easy and straightforward.

Two things kill a rotor when turning it. One, vibration; and two, incorrect mounting. Guess what? You probably figured this: Hat rotors are lightweight, so it’s much more difficult to prevent vibration, and they’re commonly mounted incorrectly on the lathe. Most of this happens because of incorrect training, or simply a shop not having the proper lathe adapters, or both. But that subject can be reserved for a whole different article.

The trouble involved with turning hat rotors was sort of a nail in the coffin for the whole process. In today’s shops, you rarely hear the sound of a brake lathe. A good majority of the rotors that are scrapped could be turned and returned to service. But a new set of rotors is less expensive than the labor to resurface an old set (hubbed rotors being the exception). Then when you factor in the reality that they quite possibly could be machined incorrectly – causing a comeback – it simply doesn’t make sense.

Replacing them is quicker, a shop makes money on the parts, technicians make more money on labor and they can get onto the next job quicker. It’s easy to think it’s wasteful when the old rotors could in reality be turned, but on the other hand, maybe it’s good for the economy. Shops make more money and parts stores make more money too. And the old rotors don’t end up polluting a landfill; they’re one of a scrapper’s favorite metals.

They provide a source of income for scrappers and metal-salvage yards. Some shops save them and haul them in for scrap themselves. It’s good pizza money for the shop … or perhaps a cold beverage of sorts.

When and Why

Technically speaking, any brake rotor only needs replaced when it can no longer be resurfaced and remain at or above the minimum thickness specification. In the real world, as you can see, this really only holds true for hubbed rotors, which for the most part we only see on older cars and trucks. Resurfacing these rotors are the only ones we can justify, when you compare the expense of replacement.

However, even if a rotor can be turned from the standpoint of thickness, there still are two other factors that can deem it scrap instead. One is cracks that occasionally result from the continuous heat-and-cooling cycle of a rotor. If a rotor is cracked, it should be replaced. The other is hot spots, which occur when rotors aren’t broken in properly. Pad material is deposited unevenly on the rotor, and these spots cannot dissipate heat properly, causing brake vibration.

Hot spots are easily identified by an obvious discoloration on the surface of the rotor. In some cases, these can be removed by resurfacing the rotor.

Selling Your Customer

Your customer probably just wants a quick answer about replacement. Here’s an easy approach: Due to the critical importance of breaking in new pads, which relies on the surface of the rotor, any time you’re replacing pads, the rotors should be replaced as well – unless it makes economic sense to turn them. And that’s the key. With any rotor problems, unless it makes economic sense to resurface, replace them. As with any brake work, don’t forget to make sure caliper and pad slides are clean and working properly, and always torque those wheels.

The post

link hidden, please login to view
appeared first on
link hidden, please login to view
.

link hidden, please login to view

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Topics

    • By Mia
      The brake pads seem to make strange noises often.
      Have you ever experienced this?
      Have you ever found out the reasons?
       
      I only know these reasons:
      Causes of noise
      ① Excessive wear of the brake disc causes noise.
      ② It is easy to form an oxide layer on the surface of brake disks in a humid environment. The change of the contact surface between the brake disc and the brake pad causes abnormal noise.
      ③ Due to the corrosion or stagnation of the caliper, the guide pin is not lubricated enough and cannot return efficiently, resulting in incomplete contact between the brake pad and the brake disk.
      ④ During the running-in period, the brake pads and brake disks are not running in enough. After hundreds of kilometers, the noise will be automatically eliminated.
      ⑤ On muddy roads, dirt and stones adhere between the brake pads and brake disks. In this case, noise is prone to be caused.
      ⑥ Brake noise is caused by brake pad formula.
       
      And some understanding of whether the brake pads need to be replaced if abnormal noise occurs.
       
      When should brake pads be replaced?
      Brake pads generally need to be replaced after the vehicle has traveled approximately 60,000 kilometers. However, the warranty for KETULLA brake pads ranges from 30,000 to 50,000 kilometers, depending on driving habits and road conditions.
      When the thickness of the brake pads approaches or falls below 0.3 centimeters, it’s time to replace them. If you hear friction noises when lightly pressing the brakes, immediate replacement is necessary. When the friction material thickness decreases to 8 millimeters, it’s advisable to inspect and possibly replace the brake pads. When the pad and steel plate thickness decreases to 3 millimeters, immediate replacement is recommended to avoid safety hazards.
      The lifespan of brake pads typically falls between 30,000 to 50,000 kilometers, depending on driving habits and conditions. Warning signs for brake pad replacement include decreased braking performance, increased braking distances, and abnormal noises. Regular inspections are necessary to determine when brake pads need replacement.
      New brake pads usually have a thickness of approximately 1 centimeter, with a usable limit of 3 millimeters. If brake pads are excessively worn, contaminated with oil, or show signs of abnormal wear or tearing, they should be replaced immediately. It’s essential to regularly check brake pad wear and replace them as needed. Replacement intervals may vary depending on the type of brake pads and driving conditions.
      Regularly inspect the thickness of brake pads, and if worn to at least 1/4 inch, it’s time for replacement. The lifespan of brake pads depends on various factors, including driving style, vehicle type, and load conditions. Regular inspections are necessary to determine when replacement is needed.
      If you also want to know some information about brake pads, you may go here: 
      link hidden, please login to view
    • By Mia
      A focus on the customer
      At Ketulla, we take pride not only in our products but also in our commitment and dedication. Since our establishment in 2000, we have been dedicated to bringing innovation and high-quality components to the automotive industry, forging close partnerships with customers worldwide.
      Through over 20 years of relentless effort, we have collaborated with over 13,200 customers in 32 countries, delivering outstanding products and services. Our market turnover has exceeded 200 million US dollars, serving as a testament to our growth and unwavering commitment to quality and customer satisfaction.
      Our brand culture is not only reflected in numbers and achievements but also in our actions and values:
      Global Perspective Win-Win Collaboration Continuous Innovation Social Responsibility Behind these achievements and honors, we acknowledge the efforts and dedication of every member of our team. We will continue to prioritize our customers, uphold our belief in exceptional quality, and forge ahead, making greater contributions to the sustainable development of the automotive industry.
      Let’s join hands and work together to create a brighter tomorrow!

      link hidden, please login to view  
      Brake Pads Manufacturer
      Ketulla is a professional brake pads manufacturer with running for 24 years, We consistently regard product quality as a crucial strategic guideline for our development. We consider our customers as part of our team, striving for excellence in both product quality and service.
      Quality Quaranteed
      All brake pads quality has passed the American LINK laboratory testing and appraisal, complies with the ECR90 Qualified standard, and has passed the ISO 16949, The production and quality control of all brake pads are strictly in accordance with ECE R90 quality standards. We ensure that we take full responsibility for the quality of all products delivered to our customers.

      EOM & ODM Avaliable
      Need to order rear brake pads and front brake pads? we offer customization:  link hidden, please login to view,  link hidden, please login to view,  link hidden, please login to view, with different pads brake formula, just send us your order list, we will send you pricelist with our  link hidden, please login to view to confirm the details.
      Compatable With 98 % Of Vehicles
      Ketulla offers you customization for different 
      link hidden, please login to view, we hold 2351 different brake pad models to meet the 98% of vehicles in the world. Such as Japanese cars, Korean cars, European cars, and Chinese cars.  
      Professional service is always available for you!

      link hidden, please login to view
    • By Mia
      Understanding the types of brake pads essentially means understanding the materials used in each type. This provides us with a clearer understanding of their names and functions and enables us to offer a reference for choosing the right brake pads.
      Friction Materials Composition
      The basic composition of brake pads currently available in the market consists of
      Shim Steel backing, steel backing adhesive friction material At KETULLA, the steel backing is formed using internationally standard 10mm stainless steel through cold pressing. The friction material comprises a binder, metal fibers, ceramic fibers, phenolic resin, aramid fibers, and various fillers, which are heat-pressed onto the steel backing. The role of the shim is to suppress vibrations, thereby reducing noise. It effectively reduces noise generated by braking. KETULLA utilizes stainless steel or high-quality heat-resistant materials for this purpose.
      We typically classify brake pads based on the proportion of key components in the friction material: semi-metallic, low-metallic, ceramic, or collectively referred to as Non-asbestos. In China, asbestos has been strictly prohibited from use in brake pads due to its significant environmental impact and adverse effects on human health. According to the revised regulation 《GB5763-2018》, this has been explicitly stated.
      Low Metallic
      link hidden, please login to view Low-metallic brake pads are the most economical option, as they typically consist of 10% to 30% metal fibers, phenolic resin binder, graphite particles, and other fillers. These fillers primarily serve to suppress thermal expansion and contraction of the composite material, thus enhancing bonding strength.
      Due to the presence of metal fibers in this formulation, research has shown that vehicles equipped with these brake pads may generate dust on our wheel hubs during braking. This dust, typically gray or black, is a byproduct of friction from the metal fibers and tends to accumulate around the wheel hubs due to its electrostatic properties, making the area appear dirty. Over time, this dust accumulation can also cause damage to the brake discs. However, the advantages of low-metallic brake pads include superior heat conductivity, strong friction capabilities, and shorter braking distances. These factors contribute to why we recommend using low-metallic formulations for truck brake pads
      “Due to their affordability, this is also why our factory sells the highest quantity of this type of brake pads. In many countries, customers primarily compare prices and performance when selecting brake pads, making them more likely to choose this type over others
      Semi Metallic
      link hidden, please login to view Semi-metallic brake pads have a similar composition to low-metallic brake pads, but with the difference that they contain 30% to 50% metal fibers. Additionally, they use larger graphite particles, which are more visibly apparent on the surface of the brake pads compared to low-metallic ones. Furthermore, their friction coefficient is slightly higher, with better heat conductivity and braking distance performance.
      They are generally suitable for use with truck brake pads. However, they are more likely to generate dust, and improper installation may lead to increased noise. In response to this issue, KETULLA continuously optimizes and adjusts the formulation, resulting in significantly reduced dust and noise generation probabilities.
      According to market feedback, the primary cause of noise is usually improper installation, indicating that our formulation optimization has been highly effective. Therefore, our purchasers can rest assured.
      Ceramic
      link hidden, please login to view Ceramic Brake Pads link hidden, please login to view Ceramic Brake Pads GF At present, ceramic brake pads are the most expensive. Ketulla’s ceramic formulation brake pads utilize high-quality ceramic fibers, graphene, and aramid fibers, without the inclusion of metal fibers. The price of ceramic fibers is significantly higher than that of metal fibers, but they offer superior heat conductivity and friction coefficients. Although there may be a slightly softer pedal feel, it does not affect the braking performance. More importantly, they result in much lower wear on the brake discs compared to other formulations, thus extending the lifespan of the vehicle’s brake pads.

      link hidden, please login to view
    • By carbdoc
      I cannot find a remanufactured brake booster for my 1978 Dodge D-150 truck with 400 c.i.d. engine to save my life!  Yes, I can send mine out for rebuilding and hope that it comes back correctly repaired (or comes back at all), but I don't want to take my truck completely out of service while I wait for it to (hopefully) be correctly rebuilt.  I would, however, gladly settle for a "loose" rebuildable core.  

      If anyone reading this has a rebuildable core that they will sell to me, I would be quite grateful.

      Jeff
    • By Counterman
      link hidden, please login to view announced a new addition to its Galvanized Brake Pad lineup. The new part introduction covers over 630,000 vehicles on the road, the company said. The company added that the brake pads are built using
      link hidden, please login to viewGalvanized steel and incorporate O.E. specified Mechanical Fusion Technology.  link hidden, please login to view New Part Number(s) & Vehicle Compatibility: NS2304  
      Expanded coverage includes the following vehicle models: Lexus: RX350 (2023), RX350H (2023-2025); Toyota: Highlander (2020 – 2024), Grand Highlander (2024-2025).
      The post
      link hidden, please login to view appeared first on link hidden, please login to view.
      link hidden, please login to view

×
  • Create New...