We have all been there, our brakes start to squeak and we automatically think we need to have our brakes checked or replaced. That is not always the case. When we have brake issues come into our shop we always ask is it a squeak, squeal or grinding noise you are hearing usually with impressions of the noise to follow. That being said lets dive in to what we should do and how we can drive the situation.
First, lets address the squeak. This noise can be caused by a number of factors. A squeak can develop over night. In many cases a squeak can be simply rust build up on a rotor after sitting overnight or after a few days of rain. Your rotor mostly bare metal especially where it contacts the brake pad and a short park in the driveway can cause it to rust from moisture in the air. This is not a safety issue and most likely you can drive on. A squeak can also be caused by the material in the brake pad itself. Brake pads are organic or ceramic and semi-metallic. The binder or compound that holds the ceramic material together can glaze and heat up causing a squeak. Also semi-metallic pads have little pieces of metal that can cause noise issues and even a squeal at times. Semi-metallic pads are also known to emit a fair amount of brake dust that usually covers your wheel so that can be a clue of what kind of pad you have on your car. Generally the part number will have a C for ceramic or a M for Metallic on your last invoice. Most passenger cars have ceramic and some SUV and light trucks still use metallic. The best way to mitigate the noise issue is to put an OEM equivalent brake pad and rotor set on the vehicle. If you do not use quality parts they will probably make some noise. In addition to all this, when having your brakes serviced, new hardware should be used. These are shims and noise clips that should be lubed and properly installed. Most DIY folks can do brakes but it does take some consideration and talent to make sure they are lubed properly and don't make noise.
Pro Tip: A warped brake rotor may not cause noise but it can give you an uneasy feeling of shaking or vibration. Generally a warped front rotor will cause the steering wheel to shake when braking while a warped rear rotor will cause the brake pedal to pulsate. Knowing this information can save you a lot of time and money. A severely warped rotor can be a safety issue but if it is a slight pulsation you feel you are most likely safe but should continue to monitor the situation. The rotor warps from heat and can be an early indication of a sticky caliper or a driving habit that might need to be changed.
Secondly your squeal can be caused by your brake wear indicator. On many new cars you have a brake pad sensor that will tell you its time to change your brakes but some older vehicles have a steel tab that contacts the rotor and causes a long drawn out squeal for the entirety of you pushing the brake pedal. If you are experiencing this it is a good time for a brake check. If it is a short pulses and goes away after a second it could be one of the issues listed in the first part. If you are unsure you it may still be a good idea to have them checked.
Lastly the grind...If you notice a grinding noise that is loud and pronounced, that is probably an indicator of a major failure. Either the pad material is completely gone or perhaps a caliper has locked up and caused the brake to remain on which caused premature failure. Either way this is an immediate issue that needs to be resolved. This is a huge safety problem. If you are able to see through your rim, you might notice a scored or extremely rough looking brake rotor. This is an indicator of brakes grinding. The fortunate aspect is depending on if a caliper is seized you may not have any more damage or more expense than if you had replaced the brakes preventatively. This for sure would mean you have to at least replace your brake pads and brake rotor.
Pro Tip: A sticky or sticking brake caliper can be evident by the car pulling to one side or the other. If when you brake the steering wheel wants to pull out of your hand you may have a sticky front caliper. If while braking the car wants to wander to one side it may be the indication of a rear brake caliper sticking. The more you know.....
All in all keeping track of your vehicle noises is important. If you can be in tune with your vehicle that is the number one way to mitigate major issues. Your cars parts generally deteriorate slowly so issues can be subtle and unnoticeable, however knowledge and planning for these issues can go a long way. So next time you get your tires rotated. Ask the shop how your brakes looked. Its a free visual inspection you should be doing with each rotation.