At what mm MUST I replace rear brakes?

Supposedly my rear brake lining thickness is 3 mm. At what point do I need new brakes? Thank you

My car has 50000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hello, thanks for your question. I would consider 3 mm to be the thickness that I would recommend for replacing the brakes. Some vehicles start out thinner than other vehicles, but under 3 mm is what most mechanics would consider too thin to know how much longer before metal to metal on the rotors. Also, brakes below 3 mm cannot dissipate heat as well and may cause the pads glue to release the pad from the backing. Hope this helps and best of luck! If you would like to have one of our local mechanics to come to your home or office to perform the replacement for you, feel free to book us for that.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

A new brake pad is 10-12mm thick. Most mechanics and dealers agree that you should replace your brake pads when they wear down to 3mm or 4mm.
Brake pads should be changed before they wear down to 1.5mm. A new brake pad will be around 10mm thick. Most manufacturers and mechanics will all agree that you should probably replace your brake pads once they wear down to 3mm.
Most manufacturers and mechanics will also agree that you should probably replace your brake pads once they reach 75% worn, or 3mm thick.
Most Mercedes Benz Front brake pads are about 12mm when new and can be driven to about 3mm of thickness.
Typically, 4mm of brake pad is recommended, so if you think they`re thinner than that, it`s time to get them checked and possibly replaced. This is the easiest way to keep on top of your brake pad condition and requires no tools or training to carry out.
We recommend you replace your brake pads at 2mm or even 3mm at times.
If a garage tells them your car has 5mm of brake pad remaining, they should be able to tell you that you`ll get another 15,000 miles out of them, or whatever it might be.
The friction material on a new brake pad is typically about 8-12 millimeters thick, and those that are ready for replacement are worn down to about 3 mm.
Most car mechanics also agree that the bare minimum brake pad thickness is 3.2 mm (⅛ inches). Any thinner than this, and you`ll need an immediate brake pad replacement to avoid brake failure.
Ideally, your brake pads should be thicker than 6.4 mm (¼ inches) for proper functioning. If it`s thinner than this, consider getting a replacement soon. Most car mechanics also agree that the bare minimum brake pad thickness is 3.2 mm (⅛ inches).
And the rear brake discs are 7.3mm minimum thickness and currently they are 6.5mm so 0.8mm under minimum thickness.
Ideally, your brake pads should be thicker than 6.4 mm (¼ inches) for proper functioning. If it`s thinner than this, consider getting a replacement soon. Most car mechanics also agree that the bare minimum brake pad thickness is 3.2 mm (⅛ inches).
The friction material on a new brake pad is typically about 8-12 millimeters thick, and those that are ready for replacement are worn down to about 3 mm.
Rear brakes typically handle less than 40% of the braking force, so they don`t generate as much heat as the front brakes. The rear brake is designed to provide stability, or else they would lock up every time you hit the brake pedal.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Low brake pedal and anti-lock brakes are not kicking in.
ANSWER : The brake pedal is working to stop the vehicle, but there may be air in the controller unit causing the ABS brakes to not function. I recommend bleeding the brake system from the farthest location from the master cylinder to the master cylinder including the ABS unit. If the brakes are still spongy after a full bleed, then the controller will need to be replaced. If you need further assistance with your brake pedal being spongy, then seek out a professional, such as one from Your Mechanic, to help you.

EPC light on 2004 Jetta. Code said brake switch faulty, but brakes lights worked. Replaced brake switch, now no brake lights.
ANSWER : Hi there. The first thing that pops in my mind beyond of what you have listed is perhaps the electrical harness attached to the brake switch. Perhaps the harness itself is damaged or you have an exposed wire, loose ground wire somewhere. You might want to have a professional mobile mechanic come to your location and complete a brake lights not working inspection to help you diagnose this issue.

Rear brake job
ANSWER : Hello, thank you for writing in. These situations are understandably questionable. The service providers at a lot of common oil changing and tire repair centers will quote you for a variety of things that can be updated. This does not always mean you are in dire need for more repairs. If braking seems to be harder, spongy, or takes longer, then you have reason to be concerned. Otherwise, you should check the amount of brake pad material left on the calipers. This can be visually inspected without too much trouble. Remove the wheel and physically measure the amount left, compare them to your vehicle specifications. It is a little early to worry about brake fluid or the rotors. However if the brake fluid is low, the rotors are warped from a hard stop, or there are obvious issues you should look into the system further. Only further inspection will confirm or deny the recommendations. For a second inspection, contact our service department to schedule an appointment.

I replaced the brake light switch. Gear lever unlocked because it had locked. Now the brakes feel hard.
ANSWER : Hi, thanks for writing in. You need to check the brake switch install adjustment. You may have the switch adjusted too tight and it is holding the the brake pedal partly down. This will cause the brake master cylinder to not release the brakes when you let off the pedal. Readjust the switch away from the pedal until you feel some free play again in the pedal. This should fix the problem. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

Hard brake pedal and rear brakes locking up.
ANSWER : Hi. I will help you with this issue you are having with your 2001 Durango. Unless you bled the master cylinder, it is possible there is still air in the system. If you car is equipped with ABS, air could have also gotten trapped in the ABS modulator. If ABS equipped, a bi-directional scan tool would be essential to manually activate the ABS system to clear air from that segment of the lines while you are bleeding the system. It is also possible that in all of this work somehow the proportioning valve has been affected causing the desired pressure differential, front versus back, to get out of spec. Using a 2,500 PSI gauge, you can check the pressures at each wheel and that will definitely give you a clue as to which brake circuit is the issue (or both), whether the proportioning valve is working properly and whether the line pressures at each wheel are within spec. Should you need a second opinion, by all means feel free to contact YourMechanic for assistance and we will diagnose and repair the issue for you.

Changed brake master cylinder, bled 10 times, and the pedal is soft The rear brakes are not locked but close. Truck now running rough.
ANSWER : You will have to bleed the brakes from the farthest location all the way to the master cylinder. There is still air in the lines causing the issue. Check the vibrations on the vehicle to see if the engine mounts are damaged or if the brakes are not releasing causing the engine to run harder than normal to overcome the braking force. If you need further assistance with your vehicle’s brake system, then seek out a professional, such as one from Your Mechanic, to help you.

Rear brakes not grabbing – 1995 GMC K2500
ANSWER : Hello. It is not in the ABS, but may be the proportional valve not giving the correct pressure split front to the rear. The vehicle never had enough pressure for the rear brakes. Have the rear shoes adjusted properly if you have drum brakes. You should check to see if there is an updated part to replace the old one. If you would like to have this done, a certified technician from YourMechanic can inspect the brake system and let you know what repairs are needed.

Have replace rear brake pads 6 times in three months.
ANSWER : Hi there:

It’s very possible that you have either a warped rotor that is causing your brake pads to constantly rub or the caliper is damaged; causing the same problem. You should have a professional mechanic complete a rear brakes inspection before the issue gets worse and creates a potential safety issue.