Mar 14

Rotor Damage Basics


We put together this short article targeted at beginners, but there is still valuable information here for even the most seasoned car-guy or gal! We’ll review the various types of brake rotor damage like squeaking, cracking, rusting or anything else that may have caught your attention. You may be surprised to find that some things are absolutely normal and not life-threatening.

1. Brake Rotors Rusting

Many non-enthusiasts who are first time car buyers are caught off guard by this and start anxiously lurking forum threads to find answers. The majority of the material that make up your brake rotors is cast iron. Therefore, due to even minor mere oxidation, rust will inevitably develop. This explains why rust will still occur even if you live in the city and only take your car out on weekends. A build up of rust is not life threatening nor is it the cause of your disc brakes squeaking. So doth sweat it if you see some occasional rust developing.

2. Brake Rotors and Brake pedal pulsation

Many of today’s vehicles have brake systems where the disc rotors are a “top hat” design. These designs are generally easier to service but at times, can create some customer dissatisfaction due to brake pedal pulsation during the brake application. Brake pedal pulsation is most often the result of disc thickness variation in the rotor. Disc Thickness Variation (DTV) is the technical term for a rotor that is not uniformly thick. Quality rotors are uniformly thick when new, and will stop the vehicle smoothly. However, due to other potential irregularities in the braking system, variation in the disc thickness can develop over time and eventually lead to brake pedal pulsation. The most common cause of DTV is rust scale or debris between the hub and rotor mounting surfaces, This causes the rotor not to sit flat resulting in excessive runout. This may not be evident once the rotor is removed from the vehicle, since its the hub mating surface that causes the problem.

3. Brake Rotor Cracking
When cracking occurs, your rotors are done, they are unsafe to drive on, and should be replaced immediately. While drilled rotors offer loads of performance braking improvements, they are also more prone to cracking. The best way around this is to invest in well known brands and trusted products that undergo tested and proven methods of manufacturing. Of course there are other causes of rotor cracking but with the quality of DBA rotors, you would have to do an awful lot to induce such damage. Unless you track your car frequently, cracking shouldn’t be an area of concern for you.

4. Brake Rotor Scarring

Scarring generally occurs when metal touches metal, due to an aggressively worn-out brake pad. The result? You get scratching and scarring on the rotor surface that affects the safety of your overall driving experience. The good news is, that this kind of damage can be machined and leveled depending on the degree of damage to your rotors. While repairing versus replacing scarred rotors is a debatable topic, you will find that your mechanic will give you the best possible opinion on the next course of action. He can see it and assess the damage properly, as there is only a limited number of times you can rub down a rotor. All rotors have a minimum thickness that they can be machined down to before needing to be replaced.

For more technical info check out our tech articles archive here.