Here are the key takeaways:
- The lowest recommended brake pad thickness is 3 mm.
- Brake pads thinner than 3 mm are considered dangerous by mechanics.
- The lowest legal brake pad thickness is (usually) 1.6 mm.
- A new front-wheel brake pad should be about 12 mm.
- A new rear-wheel brake pad could be between 8 and 10 mm.
- Use brake pad thickness gauges or simple tools to measure them.
Table of ContentsShow
Brake Pad Thickness
With worn-down brake pads, the brakes won’t work – at all. The only way you’ll be able to bring the car to a halt is with engine braking and, when necessary, the emergency brake.
Luckily, you shouldn’t ever reach this point. Regular checks and metal warning layers give you months of warnings.
Brake pad thickness should be checked as often as reasonably possible. It is an integral part of stopping your car, after all.
In short, brake pad thickness is crucial to keep an eye on. In this simple guide, I’ll explain brake pads’ minimum, new, and ideal thicknesses. I’ve also included a custom chart.
Let’s get started!
How Do Brake Pads Work?
Brake pads have a metal backing plate with a high-friction surface bound to them. Each wheel has two pads – one for the outside and one for the inside. They fit inside the brake calipers.
When you press the brake pedal, hydraulic brake fluid forces the piston (or pistons) in the caliper towards the spinning rotor. Its frictional surface pushes into the spinning rotor face.
As the surfaces touch, friction slows the rotor down. In turn, this reduces the rotational speed of the wheels and slows (or stops) the car.
Note that brake pads and discs get very hot due to all the friction, especially during hard braking.
That’s why you see racecar rotors glowing orange as they approach corners. If they get too hot, you’ll experience what’s known as brake fade: when the brakes stop working properly. Many modern rotors are ‘vented’ to counter this.
How Thick Should A Brake Pad Be?
A thick brake pad makes all the difference when stopping. The more material there is, the easier it is to absorb and dissipate the frictional heat.
In contrast, if your pads go below the recommended brake pad thickness, they’ll get too hot. Your car will have drastically reduced stopping power.
This is hazardous to yourself, your passengers, and other road users (including pedestrians).
In severe cases of neglect, the frictional material will completely wear away. This leaves the metal backplate to press against the rotor face.
If this happens, you’ll hear a horrible screeching noise (far worse than the shrill warning noise). The car will also struggle to stop.
Check out this brake pad measurement chart for a clear graphic to explain what’s ideal, acceptable, and dangerous.
What Is The Ideal Thickness Of Brake Pads?
How thick should brake pads be? Ideally, 6 mm or more. Once you go below 6 mm, the brake pads stop performing so effectively (in most cases).
They’ll be alright for a while – there’s usually no need to replace them. Follow your mechanic’s advice.
When your brake pads reach 3 mm, they need to be changed. It’s not the legal cut-off, yes. But most experienced mechanics will agree that this is the minimum safe brake pad thickness.
What Is The Legal Minimum Brake Pad Thickness?
Realistically, you must always keep your brake pads above 3 mm.
The legal minimum thickness for the steering axle is 1.6 mm for hydraulic disc brakes and 3.2 mm for air brakes. As always, measure this from the steel backing plate to the lowest point of the pad.
It may be the minimum legal requirement, but that doesn’t mean you should let your brake pads wear down to this point. At 1.6 mm, your brakes will be dangerously ineffective.
Brake manufacturers will tell you when the pads and rotors need to be replaced. It’s best to follow their guidelines.
When Should I Check Brake Pad Thickness?
You should check brake pad thickness about every 5,000 miles or a couple of times per year. Mechanics should inspect the brakes every time you visit. It’s best to ask specifically to make sure.
Generally, you should expect brake pads and rotors to last a long time. 40,000 miles (depending on your driving habits and techniques) is a reasonable average.
If you hear a shrill screeching noise from your wheels, it’s almost certainly the brake pads. This is an indication that they’ve reached the minimum legal thickness.
Take your car to a technician immediately and have the brakes replaced.
It’s recommended to replace pads and rotors at the same time.
How Do You Measure Brake Pad Thickness?
Measuring brake pad thickness is a relatively simple job, but it often involves removing the wheels. You’ll need a jack, axle stands, breaker bar, wheel nut sockets, and a torque wrench (at least) for this.
Take a measuring gauge tool. You’ll need to find the specific instrument that snugly fits between the brake pad’s backing plate and the rotor face.
This reading is your brake pad thickness.
If you’ve taken the brake pads off, you can use a more genetic method. Mechanics often use a tire tread depth gauge against the backing plate to measure pad thickness. Take readings in several locations.
Torque the wheel nuts back up to the appropriate level when replacing the tires.
Note: It’s also possible to measure brake pad thickness without taking the wheels off. However, this can be challenging to do to any degree of accuracy. It’s almost impossible to measure the outside pad unless you have alloy wheels. You might be able to check the inside one by turning the steering wheel to full lock and getting underneath the vehicle.
Do Some Brake Pads Last Longer Than Others?
Not all brake pads are created equally. It’s not true in every case, but you’ll generally get what you pay for.
Budget brake pads tend to be made from cheaper materials that are less effective at dissipating thermal energy. More expensive parts should perform much better.
That being said, watch out for branding. You don’t need to get the best brake brand – most people can’t see them anyway. Instead, focus on the best brake pad materials, ensuring they’re OEM.
High-performance brake pads aren’t always necessary, especially if you drive a small, light hatchback. However, look for ceramic or metallic options for the best stopping power. Ceramic pads are most efficient under stress since heat is less of an issue. Still, they’re often costly, and you’ll need to purchase high-quality rotors to match. As such, metallic brakes are the most common choice for daily drivers.
Organic brake pads are also available. Once made from asbestos (not anymore!), these options tend to be within budget ranges. They’re cheap but won’t last as long or perform as well, but they’re still legal and will function reasonably well.
How Thick Are New Brake Pads?
New brake pads should be 12 mm thick. If you’re changing the brakes on a rear wheel, you might find that the pads are slightly thinner (8 to 10 mm).
If you’d like to check for yourself, you can measure brake pad thickness before inserting them into the caliper. A simple rule or tape measure will do.
You can see these readings on the brake pads thickness chart above.
Why Won’t My New Brake Pads Stop The Car?
Check out the guide below for more information on the costs of changing brakes.
When you replace the pads (ideally with the rotors), you might notice that the car struggles to stop. This happens when the brake pads are ‘digging in’ to the rotors, creating a groove in which they’ll soon settle.
There shouldn’t be anything wrong with the brake pads themselves.
The mechanics should take the car for a test drive around a safe, empty car park (or something similar) to bed them in. They’ll slam the brakes on several times, forcing the pads to dig into the rotor.
If, when you get your car back, it still feels like it’s struggling to stop, take it to a safe but secluded location. Do this yourself a few times.
The stopping power should soon be back to normal.
Is the problem persisting? The brakes might need bleeding, or the calipers could need replacing.
It’s always imperative to ensure your brake pads are in good condition. They aren’t parts you usually look at, so having them specifically inspected is a must.
Once they get below 6 mm, consider having them swapped out for new ones. Never let them go below 3 mm.
Of course, new pads should be 12 mm, and they should last you for a few years. They might need replacing earlier if you tend to brake very hard a lot of the time.
The best way to ensure your brake pads work well and last for a long time is to drive and brake smoothly. Only slam the pedal down if emergency calls for it.
To take a brake pad measurement, get yourself some measuring gauge tools. These are by far and away the most straightforward way to do it.
Brake pad replacement is pretty inexpensive as far as automotive jobs go. It should be done whenever necessary to keep your car and everyone in and around it safe.