Identifying and Preventing Warped Rotors

November 29, 2023

Whether they’re blank, drilled, or slotted, brake rotors play a critical role in stopping the vehicle safely. When force is applied to the brake pedal, the pads are compressed against the rotor creating friction stopping power. If the surface of the rotor becomes warped, this can cause a host of braking issues. So how does rotor warping happen? What are some of the side effects and how can you help prevent it?

A tremendous amount of heat is generated through braking and the rotors need to be able to dissipate that heat quickly in order for the brakes to stop the vehicle properly the next time they’re activated. Over time the repeated exposure to high temperatures can begin to warp a rotor surface. This may happen more quickly if the rotors are of a lesser quality. As the rotors begin to wear their surface thickness will decrease and when extreme heat is applied to that thinning surface warping can occur.

While your customers may not be able to see that their rotors are thinning or warped, they’ll be able to feel it. That’s why it’s so important to always recommend that brake pads and rotors are replaced at the same time. This will ensure that things wear evenly and the customers maintain optimal stopping power for the lifespan of the parts.

So what does a warped rotor feel like to customers? There are two common symptoms.
  1. If a front rotor is warped, customers will feel a pulsation when pressing the brake pedal and or shaking of the steering wheel.
  2. If a rear rotor is warped, customers will often feel a vibration beneath their seat while they’re braking.

If you suspect a customer’s issue could be due to a warped rotor, ask them what they feel. Pedal pulsation and a shaking wheel or vibration beneath their seat. Replacing rotors can be an expensive but necessary repair depending on their condition.

So how can we help avoid warped rotors when vehicles come into the shop?
  1. Keep rotors clean
    If you inspect the rotor and see oil or shards of metal on its surface, remove the rotor and wash it thoroughly. Do not use brake cleaner to wash the rotor. Rotors should always be thoroughly cleansed with dish soap and warm water and then dried.
  2. Look for the minimum rotor thickness
    Use a micrometer to measure the rotor’s thickness against the manufacturer’s minimum specifications and be sure to measure 10 millimeters into the rotor’s outer circumference eight times around the surface at 45 degree intervals.
  3. Watch for runout
    Excessive runout is when the rotor wobbles because it’s not sitting at a perfect right angle to the wheel hub. Every time the rotor spins, only a small portion of its surface will make contact with either of the brake pads causing uneven wear, pedal pulsation, and more.

Remember, rotors and pads go hand in hand which is why they should always be inspected together. If your rotor is what’s causing your customer’s issue and replacement is necessary, be sure to recommend new pads at the same time.

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