One of the most important components of your car's braking system is the brake pads. Without brake pads, your car won't be able to stop. The brake pads are a part of the disc braking system and this allows you to slow your car to stop it. Brake pads wear out, just like any other material that's constantly used. And a part of understanding how the braking system works is to find out the minimum brake pad thickness.
Before we go into the allowable minimum thickness of the brake pads, let’s first explore how the braking system works and why brake pads wear and tear over time.
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Understanding the disc braking system
Most modern cars have a disc braking system to help the driver slow and stop their cars safely. This is made up of a component known as the brake caliper that has pistons and the brake pads. You will also find a spinning disc that moves near the wheel as the car is moving.
When you press on the brake, the caliper presses the brake pads and the pad pushes the brake disc. When the pad hits the disc, friction is created and this slows down the wheel.
What is a brake pad made of?
As you can see, the brake pad is a vital part of a car's braking system. It is made of steel plates, friction components, rubberized coverings, shims, and thermal coatings. No doubt that these are very strong, durable materials, but no material lasts forever, especially when you drive more frequently than others.
And even if you seldom drive your car, there will be a time when these pads need replacement. Brake pads are used every time you step on your brakes. How long will 4mm brake pads last? Usually, 4mm brake pads will eventually wear after your vehicle has covered 50,000 miles. Some brake pads will give you more mileage and these are usually thicker than regular brake pads.
So what is the minimum brake pad thickness?
So every time that you press on the brake pedal, the pads will rub on the disc, and some portion of the surface of the pad is removed. Eventually, the pads wear down. When you say the minimum brake pad thickness, this pertains to the thickness of the friction material.
If the friction material becomes too thin, this won't be able to stop your car, let alone slow it down when you press on the brake. If this friction material were to wear down and dissipate, your brakes will fail.
The minimum brake pad thickness will depend on the manufacturer. Usually, you should replace your brake pads when these are only 3mm thick. How much brake pad left is safe? Some say that you can still get a good response when the thickness is a mere 2mm but this is dangerous as the metal will soon become exposed. If you still won't change the brake pad at 2mm, you will eventually hear a very loud squealing sound when you press on the brake pedal. This is the sound of metal pressing on the disc.
So, it’s safe to say that the minimum brake pad thickness is between 3 to 4mm. Anything lower is dangerous. Also, broken brake pads will eventually crack as it can’t deal with the heat created by friction between the two metal materials.
When to replace brake pads?
A question you may also have is how thick should brake pads be? Or how many mm is a new brake pad? New brake pads are usually 10 to 12 mm thick. This is the standard thickness for new pads. You should replace your brake pads when these reach 3 to 4mm.
How fast your brake pads go from 10 to 3mm will depend on how aggressively you drive. It is also based on how often you use your vehicle and how often you use your brakes. Take note that not all brake pads are created equal as some brake materials last longer than others.
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Symptoms that your brake pads need replacement
You should have your brake pads replaced as soon as you find the following symptoms:
- Brakes take longer to respond
If you've noticed that your brakes take a lot longer to respond, then you must have your car inspected. There are many reasons why this could happen and one of these is worn out brake pads. A technician will likely inspect the brake system and change the brake pads. This is SOP in any brake system inspection.
- Loud screeching sound when the brake pedal is pressed
Very loud screeching when the brake pedal is pressed means that your pads have reached the point of no return and soon, you won’t be able to control your vehicle! Have your pads replaced ASAP.
- It has been too long since your brake pads have been replaced.
If you remember when your pads were replaced and it has been too long since then, then it could be time to replace them again. Don’t wait till it’s too late.
Brake pad replacement is a part of any professional brake system check. When you visit a professional technician, your brake pads will be checked for thickness using a special brake lining thickness gauge. This tool has three different colors representing the varying amount of thickness. There's green for thick pads, yellow for moderately thick pads, and red for close to wearing pads.
When your pads are in the green zone, this means that these are close to new. Yellow means that the pads are still OK. When your pads are on the red zone, this means it's time for a replacement. The cost of pad replacement depends on the type of the pad and the vehicle you have.
The minimum brake pad thickness should only be from 3 to 4mm, no more no less. You should never compromise safety over brake pad replacement. Have your brake pads and brake system checked today.
James is a certified auto technician specializing in commercial vehicles. With 30 years of experience under his belt, James has encountered almost every type of automotive issue there is! Besides his day job at the repair shop, he is also an amateur race car driver.