Automotive vehicle brakes are an exact science and after several thousands of mile of driving sometimes a brake vibration occurs which is due to several things and can be remedied as follows:
First of all it is important to detect if the vibration is coming from the front brakes or the rear. Generally front brake vibration can be felt through the steering wheel and rear brake vibration is felt in the seat, the brake pedal and the bodywork of the car generally. Brake vibration can become so severe that it detracts from effective stopping power of the vehicle. Cases have been reported where drivers actually reduce their braking pedal effort to try and prevent the steering wheel from shaking due to this brake vibration and obviously this is a major safety issue.
The brake vibration is coming from the brake rotor in 99% of the cases although it may have been caused by other components within the car such as a tyre that is not in balance, a seized or dragging brake caliper or s suspension part. However for economy reasons drivers should always consider that the brake vibration is actually coming from the rotors as this is the most common cause by far.
The problem starts out with brake rotor run out and checking for brake rotor run out can be achieved quite simply with the run out gauge shown here on the left. If the run out is more than 0.004 inches or 0.1 mm there is an issue to resolve. However even considering that rotor run out may have started the process to experience brake vibration the run out itself is not so much the problem. What happens is that when a car develops or has rotor run out it develops a condition known as DTV or Disc Thickness Variation which is caused when the rotor nudges against the pad each rotation as the car is being driven and the brakes are not applied. This gradually wears a small “thin spot” on the rotor and it is this thin spot that causes brake vibration as the brake is applied and the thick-thin rotor tries to pump the caliper pistons back in the brake system. The harder you press the brake pedal the worse the vibration. Alternatively a driver of your car may have nudged a kerb stone or hit a pothole on the road which throw out the alignment of your vehicles steering and promotes brake rotor run out, which leads to the condition DTV mentioned above and there you have your brake vibration.
The easy and quick way for a mechanic to remedy this is to replace the rotors and hand you a nice fat bill and smile. However your problem will return in 3000-4000 miles exactly and you will be buying more rotors at which point the next or same mechanic will tell you that you purchased low quality rotors. Mechanics may even say that your rotors have WARPED which is frankly impossible and indicates an uneducated mechanic.
The REAL way to solve the problem once and for ever is by taking your car to a garage that has an ON CAR BRAKE LATHE as this machine is the ONLY way to correct both DTV and geometry or alignment issues with your vehicle. The problem will then go away until the next time you have to replace your brake rotors, many thousands of miles down the road. That is unless you bash the kerb again.