If the steering wheel shakes when the brakes are applied, the brake rotors most likely have excessive side to side run-out or they are more commonly known as being warped. Auto techs call this brake shake or brake pulsation. Brake rotors being warped is not a dangerous condition by itself, but it can be very annoying. The brake pads may not need to be replaced, but if they are more than half worn it would be a good time to consider replacing them. Most shops will check brakes for free, it’s best to make sure they use a micrometer to measure the thickness of the rotors to verify if they are legally able to be machined (also known as turned or resurfaced).
Replace or not. Many vehicles today have very thin rotors from the factory, depending on the thickness there may not be an option to machine them. Many replacement rotors are low priced depending on the make and model of the vehicle. It may be a good idea to replace the rotors if the replacements are priced well, instead of machining the old ones. After machining the rotors they are physically thinner and more susceptible to being warped again. In the past I owned a vehicle that warped rotors frequently. I would machine them myself using the brake lathe at the shop I worked at and the rotors would warp again in about six months time. I finally bought some aftermarket replacement rotors for around $30 a piece and put those on and never had anymore pulsation problems.
Types of Brake Lathes. There are two types of brake lathes. There is the conventional brake lathe that the technician uses to machine the rotor off the vehicle. And there is the on the car brake lathe used to machine the brake rotor on the vehicle. The best way to machine brake rotors is on the car. The reason is because of the possibility of other components having run-out. When rotors are machined on the car, any run-out in the wheel hub is compensated for. The result is a much better cut that allows the rotor to be machined much more precisely. Rotors that are machined on the vehicle have less re-occurrences of being warped as quickly when compared to rotors being machined off the vehicle. So if possible consumers should opt to find a repair shop that has the capability to machine rotors on the car if needed. Auto repair shops that have on the car brake lathes realize the importance of having the right auto tools and equipment to service their customer’s cars properly.