Dangers of Warped Rear Rotors

Safe driving involves the cooperation of entire automotive systems, a little maintenance and the ability to know when something is wrong with your car. Brake systems are an important part of driving safety and are affected by rotors, pads, calipers and a bevy of other gadgets that make your car stop when and where you need it to. However, rotors provide a base for the system to work around and, like any auto part, can wear down and lose reliability over time.

Increased Stopping Time

A warped rotor is simply a brake rotor that is no longer even, has pitting or scratches along its face or is misshapen in any way that compromises its smooth, even surface. When these defects appear in a rotor, its contact surface with the brake pad can be decreased, reducing the amount of friction the brake pad can apply to the rotor to stop the wheel from turning. With reduced friction, stopping time is slightly increased, meaning that the distance your car travels after you apply the brakes is also slightly increased. On a rotor attached to the drive axle of the car (front or rear), the increased stopping time can have even more noticeable effects.

Brake Failure

A warped rotor's reduction in friction and the uneven nature by which it moves the brake pads back and forth can actually cause temporary brake failure. Brake fluid works in a hydraulic manner to apply pressure to brake pads and force them to tightly squeeze the rotors. This action causes the rotor to stop moving, but relies on the fluid to be compressed and without bubbles or foam. According to mechanic and "The Washington Post" contributor Pat Goss, warped rotors can cause the brake pads to wobble back and forth, foaming up the brake fluid and robbing the brake system of its hydraulic pressure. This can cause temporary brake loss during a panic stop (when a driver mashes the brakes in a panic).

Vehicle Misalignment

Warped rotors can also cause vehicle misalignment by wobbling the pads and calipers. This back-and-forth movement and forced pulsing when the brakes are applied contribute to wheel and axle wobble, as well as brake system movement that is not intended for the vehicle. This movement can throw off your tire alignment, caliper action and even brake pad alignment, reducing stopping and steering accuracy. Extended wobbling and pulsing during brake application can actually cause axle, tie rod and strut wear on the car.

Vehicle Damage

Driving and applying brakes on a warped or defaced rotor can cause slight to severe damage to the automobile. Initially, warped rotors cause brake pads to wear out unevenly or more rapidly, shortening the life of pads significantly. After extended driving, warped rotors start to damage the pad clips, rattle the calipers and even force the pad backing into the rotor, causing even more rotor warping and scratching. In extreme cases, the pits or scratches in a warped rotor can catch pads and calipers and bend or break them, rendering the brake on that particular wheel useless.