As an integral part of stopping your car, brake pad thickness should be checked as often as reasonably possible. You’ll need a mechanic to remove your wheels. If you’re comfortable around cars, you could do this yourself.
Brake pads are inserted into the calipers. They’re then pushed onto the spinning face of the rotor (otherwise known as the “disc”). The rough front of the brake pads produces an opposing force in the form of friction, slowing the wheel’s rotational speed.
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.
All of this means brake pad thickness is crucial to keep an eye on. This guide will explain brake pads’ minimum, new, and ideal thicknesses, with a chart included.
Let’s get started!
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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 pushes the piston (or pistons) in the caliper towards the spinning rotor. The brake pad’s metal backing plate backs into the piston. Therefore this action pushes the frictional surface into the rotor’s spinning face.
As the surfaces connect, friction slows the rotor down, reducing the rotational speed of the wheels and slowing or stopping the car.
Note that brake pads and discs get very hot, especially during hard braking, due to all the friction. That’s why you see racecar rotors glowing orange as they approach corners. Many modern rotors are “vented” to counter this since if they get too hot, you’ll experience what’s known as brake fade: when the brakes stop working properly.
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.
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 will most likely inspect the brakes every time you take your car in, although you should always specifically ask.
Generally, you should expect brake pads and rotors to last a long time – on average, probably about 40,000 miles (depending on your driving habits and techniques).
If you hear a shrill screeching noise coming from your wheels, it’s almost certainly an indication that the pads have reached the minimum legal thickness. Take your car to a technician immediately and have the brakes replaced.
It’s highly 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 minimum, for this.
It’s possible to measure brake pad thickness without taking the wheels off – but it can be challenging to do it accurately. It’s almost impossible to measure the outside pad unless you have alloy wheels. You might be able to check the inside pad by turning the steering wheel to full lock and getting underneath the vehicle.
Take a measuring gauge tool and find the specific instrument that fits snugly between the brake pad’s backing plate and the rotor face. This reading is your brake pad thickness.
If you’ve taken the wheels off, make sure you torque them back up to the appropriate level when replacing them.
How Thick Should A Brake Pad Be?
A good brake pad thickness makes all the difference when stopping. The more material there is, the easier it is for the pads to create and dissipate the heat produced by friction.
In contrast, if your pads go below the minimum recommended brake pad thickness, they’ll get too hot. Your car will have drastically reduced stopping power. It’s essential to avoid this since it’s hazardous to yourself, your passengers, and other road users (including pedestrians).
In serious cases of neglect, the frictional material itself will completely wear away, leaving just the metal backplate to press against the rotor face. You’ll hear a horrible screeching noise if this happens, and 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 Legal Minimum Brake Pad Thickness?
Realistically, you must never let your brake pads go below 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.
Just because this is the minimum legal requirement doesn’t mean you should ever let your brake pads wear down to this level. 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. We’ll get into the ideal thickness of brake pads below.
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.
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 probably be alright for a little while if you’re on a tight budget – there’s no fierce urgency here.
When your brake pads get to 3 mm, they need to be changed. It might not be the legal requirement, but most experienced mechanics will agree that this is realistically the minimum safe brake pad thickness.
Why Won’t My New Brake Pads Stop The Car?
For more information on the costs of changing brakes, check out the guide below.
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, relatively empty location and do this yourself a few times. The stopping power should soon be back to normal.
If the problem persists, the brakes might need bleeding, or 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. Don’t slam the pedal down unless an 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 isn’t too expensive and should be done whenever necessary to keep your car – and everyone in and around it – safe.