How do I know my brakes are worn out?

Slotted Brembo brake rotor, pads and oversized caliper on a late model Lexus RC-F sports car.

Modern automobiles are equipped with very sophisticated braking systems with acronyms like ABS, VSC, BAS, ABA, EBD, SBS, and so on, but the basic components required to stop the vehicle have pretty much remained the same, although they look very different from their ancestors when brakes were first installed on an automobile all the way back in 1902. You require a component that rotates with the wheels of the vehicle, in this case a drum or a rotor, a mounted clamping device and friction material, which would be your brake shoes or brake pads. Although, most common automobiles have switched over from the drum and brake shoe combo to a more innovative and cheaper brake rotor and pads setup, the drum/shoe setup still does exist in the automobile world in some antique and economy models.

A brake disc with outboard pad in place and inboard pad in the mechanic's hand.

A quick way to know if your brake pads are worn out is to quickly look through the rims and look at the friction material on the brake pads left. But that doesn’t tell you what’s happening on the dark side of the caliper. But wait, what’s a caliper?

A quick visual display of how brakes work in a disc brake and pad setup.

A 2 piston floating on the left and 4 piston fixed caliper on the right.

A caliper is the clamping device that squeezes the brake pads on either side of the rotating brake disc (rotor) to slow down, hold the vehicle in its place or help you save the neighbor's cat when you jump on that brake pedal. It can be made of various different metals and comes in many different shapes and colors. Here in Ontario, and almost everywhere else in Canada, most of them look like an old piece of metal with some surface rust peeking at you through the rim spokes. There’s not much one can do to check it’s proper functionality unless you put the vehicle up on a lift, remove the wheels and inspect it visually and physically.

So, coming back to checking the life remaining on your brakes, it appears that it’s not just a simple look at the outboard brake pads and playing a guessing game. A thorough brake inspection will include inspecting the friction material remaining on the inboard and outboard brake pads/shoes, quality, thickness and runout of the brake rotors/drums, ensuring the pads aren’t seized in the pad bracket due to corrosion, broken, rusted or missing shims, springs, adjusters and other hardware, inspecting the caliper for rips or tears in the rubber dust boots and the cylinder for proper movement without sticking and leaks, slider pins for signs of corrosion and adequate grease and also, the brake fluid that transfers the pressure from your foot to the brake calipers and the brake lines that it uses. A stich in time saves nine, but a brake inspection on regular basis or before a long trip can save hundreds, if not more, amount of dollars.

A proper way of inspecting brakes is to remove the caliper and check the amount of friction material left on both inboard and outboard brake pads. The movement of slider pins, brake cylinder and pads in its bracket can also be inspected at the same time. The thickness and condition of the brake disc should also be noted.

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