Brakes on a car operate in the same way as a skater slows down on a skateboard. By dragging their foot along the ground and creating friction. We explain this better in this blog post. This friction causes 2 big factors that lead to the machining or replacement of the brake rotors, heat and wear. Though the pads material and the rotor are usually both made out of metal-based compounds, the friction of the pad against the rotor actually causes the rotor to wear and become thinner, the same way that sandpaper removes wood for a woodworker.
Because of this, most brake rotors are designed with a minimum thickness which the rotors must be replaced at. The other reason that many rotors need to be replaced or machined is heat. As the metal gets heated and cooled over time, the metal rotors tend to warp and become not-round. For example, if you drove through a puddle. These specifications are usually stamped on the rotor, and can also be found in repair manuals. The specification allows for a certain amount of wear to occur before the rotor reaches the end of its service life.
Advertisement Finally, if you are replacing rotors, should you replace troublesome composite rotors with solid cast rotors? This may or may not affect steering and handling on some vehicles. Service: Servicing Custom Wheels. Service: Cavitation: Killer of Water Pumps. Magazine Current Issue Past Issues. Connect with us. Advertise Subscribe Contact Us.
By Larry Carley. With that in mind, resurfacing can restore the friction surface on worn rotors to like-new condition, unless a rotor is worn down too far to be safely resurfaced or has cracks, deep grooves, severe rusting, hard spots or other structural defects.
Premium rotors typically use the same casting configuration as OE same number of cooling ribs between the faces and same pattern. Why Machine? Rotor life can suffer, though, when overly abrasive pads are installed. Most rotors today are manufactured with 0. The same results can be achieved using a conventional bench lathe, but this requires a multi-step process. If you can feel the grooves with your fingernail, the rotor is probably too rough and should be resurfaced or replaced.
Finally, if you are replacing rotors, should you replace troublesome composite rotors with solid cast rotors? In this article:. Click to comment. Watch a webinar for free on-demand! Listen to the latest episode on "What's Treading". By Madeleine Winer. Advertisement For best results, replace original equipment rotors with ones that are the same or better. Premium quality rotors meet or exceed all OEM specifications — something which is not true of many economy rotors. Premium rotors typically use the same casting configuration as the original same number of cooling ribs between the faces and same pattern.
But the trade-off may be reduced cooling performance. If an OEM rotor has 37 ribs and an economy rotor has only 32, cooling may be reduced 8 to 10 percent. This can make the rotors run hotter, which in turn shortens pad life. Laboratory tests have also shown that some economy rotors are much noisier than OEM rotors or premium replacement rotors 85 decibels versus 50 decibels.
Advertisement The metallurgy of replacement rotors is also important. The rate at which iron cools in a mold must be closely controlled to achieve the correct tensile strength, hardness and microstructure. If a rotor is too soft, it will wear rapidly. If a rotor is too hard, it is more likely to crack.
If harness is uneven, the rotor will wear unevenly or develop hard spots that cause a pedal pulsation. A cheaply made rotor looks the same as a premium rotor. Advertisement Finally, if you are replacing rotors, should you replace troublesome composite rotors with solid cast rotors? Cast rotors are cheaper, and are more rigid than composite rotors.
But the center hat section of a solid cast rotor is thicker and changes the steering geometry scrub radius and toe alignment slightly. This may or many not affect steering and handling on some vehicles. Wheel End: 4X4 Locking Hubs. Digital Edition. Contact Us. Shop Owner. Special Content Video Podcasts Webinars. Magazine Current Issue Past Issues. Connect with us. Advertise Subscribe Contact Us. By Larry Carley Carley. By Brake and Front End Staff.
By Andrew Markel. Sponsored Content. By Larry Carley. The answer, I think, is two-fold. The second part of the answer involves money. Rotor life can suffer, though, when overly abrasive pads are installed on a vehicle. A brake pedal pulsation or shudder is one of the most common symptoms that indicates rotor trouble. Some vehicles are much more sensitive to runout than others.
Most service specifications also say there should be no more than. Most rotors today are manufactured with. The same results can be achieved using a conventional bench lathe, but it requires a multi-step process. If you can feel the grooves with your fingernail, the rotor is probably too rough and should be resurfaced or replaced.
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