For the front brake pads, ensure that you apply a strong handbrake, then lift the front part of the car and place it securely on a stand, and finally remove the front road wheels. As for the thickness of the friction material of every pad, it shall not be less than the specified thickness if it is worn out to such state; moreover, if any of the pads is close to the minimum thickness, it is advised to replace all the four pads. To rule out the possibility of any malfunctioning, it might be necessary to take out the brake pad so that one can have a close look at the status of the caliper and the disc of the brake on both faces. For the rear brake pads, first turn off the engine, then apply the handbrake, and parking the car on a level ground apply the brakes for sometime and switch off the engine, now apply wheel chocks on the front wheels, now using a jack lift the rear part of the car and place it on the axle stands Next remove the rear roadwheels and do the same checks and procedures we do on the front brake pads.