What Causes Warped Brake Rotors?

When the brake rotors of your automotive are warped, it doesn’t necessarily mean that the circular discs are bent out of practice. It’d feel that way with all of the shuddering and vibration when braking, but those alarming sensations have more to do with uneven rotor surface — and you may thank your brake pads for that. In brief, a warped rotor means there’s brake pad residue buildup on the disc, and people many peaks and valleys are the basis explanation for vibrations that may otherwise be blamed on warped rotors.

You most likely understand how your automotive’s brakes work: pressing the brake pedal engages the calipers and brake pads to persist with the rotors, and the automotive stops. Easy, right? Nevertheless, there’s more at play. The friction material in various kinds of brake pads comprises fibers, resins, and other materials that bond to the rotor face. After installing recent pads and bedding the brakes, those fibers and resins leave a somewhat sticky residue on the rotors, which provides what’s called stiction braking along with the friction generated by grinding the brake pads against the rotors.

Once you step hard on the brakes, the extreme heat and friction remove a number of the residual fibers sticking on the rotors, making a high spot — an uneven area — on the rotor face. One high spot will turn into many as you brake, drive, and stop abruptly to avoid that stray kitten on the road. In turn, those quite a few high spots cause the pulsing sensations and juddering related to warped rotors.

When you encounter vibrations or shuddering when applying the brakes, it is probably not too late to avoid wasting the rotors from totally warping. Usually, rebedding the brakes will restore the braking feel and eliminate those nasty vibrations. Rebedding is basically accelerating to about 50 mph and slowing all the way down to 10 mph repeatedly to heat the brakes — without coming to a full stop. After five to seven stops, drive normally without hard stopping for just a few miles to chill the brakes, and also you’re done.

One other good practice is to avoid pressing and holding the brake pedal when at stoplights, especially if the brakes are scorching hot. This prevents the pads from leaving high spots on the rotor. In fact, gentle braking habits will go a good distance in extending the lifetime of your automotive’s brake rotors, as will ensuring that the wheel nuts are tightened and torqued to the right specs. Loose or overtightened wheel nuts may cause the rotor to rest unevenly and create pressure points, which is able to inevitably warp the rotors.

Very similar to how frequent oil changes will prevent sludge buildup, periodic inspection and brake servicing may help detect warping early and stop costlier damage. For reference, the brake pads in a mostly city-driven automotive can last 30,000 to 35,000 miles, while vehicles driven totally on the highway may have pads that may last 80,000 miles or more. Meanwhile, the brake rotors can last even longer before needing resurfacing or substitute.

Warped brake rotors may be resurfaced, but not all old rotors are ideal candidates for doing so. Brake rotors have discard levels stamped on the hub, which specify the minimum thickness for safer operation. If the thickness after resurfacing falls below the discard level, replacing the rotor is preferable to resurfacing. As a general rule, it’s secure to resurface the brake rotor if the thickness is at the very least .050 inches greater than the discard level.

Resurfacing shouldn’t be an option if there’s heavy corrosion on the perimeters of the rotor, if the contact surface has deep grooves or scarring, or if there are multiple bluish stains on the rotors. Depending on the make and model of your vehicle, substitute brake rotors typically cost $50 to $80, while resurfacing would cost about half as much. Experts recommend recent rotors each time you are replacing the brake pads, but it surely’s secure to reuse the old rotors if the contact surfaces are still relatively flat and smooth.