Why you should replace your brake rotors...

These rotors are too thin, notice ridge around outside

In modern disc brake systems, brake rotors are these big steel looking discs that rotate with your wheels that the brake pads act on. Your brakes are frictions devices, so as a result of what they do for a living, they generate heat. And lots of it.

Most people don't usually have any reason to think about brake rotors until some shop tells them they need to be replaced, almost always with a hefty price tag. Replacing them is optional in a way. you can always say no. And sometimes you should, but there are times when you should just pony up the dough.

Brake rotors wear just as brake pads do, but being of some durable material (like cast iron), it takes longer to wear them down. All manufacturers have a minimum specification for rotor thickness, which is derived from their ability to get rid of heat. If your brake system gets too hot, various things happen, none of which are desirable.

The most annoying thing that happens is the brake rotors can warp. The consumer will know when this happens as the brakes can get an annoying shudder when you apply the brakes, and if on the front, can shake the steering wheel also. It's not hard to sell these people brake rotors.

The worst thing that can happen is you boil the brake fluid. Granted this doesn't happen often, but todays expressways bring speeds and panic stops that are extremely hard on brakes. Too many hard stops on brake rotors that are too thin can spell disaster. Once the brake fluid boils, you brakes are seriouly compromised, as the boiling produces air bubbles that can't be compressed like brake fluid can. And as the front brakes do most of the work, it will usually be the front brakes that fail.

All modern cars have their brake fluid split up into 2 systems, so that if one fails the other will still be there to stop the car. And this does work, but the rear brakes can barely carry the load of stopping a 3000 lb car, and modern parking brakes are no help. They keep you car from rolling down a hill, and that's about all.

So when your shop tells you that your rotors need replaced, ask them to show you the measurement or the reason for replacement. You don't need to replace your rotors on every brake job (like some high profile shops like to do) but you will need them sooner or later. Also, a brake fluid flush every 3 years will keep the boiling point up as high as possible.