How to Inspect Brakes
Brakes save lives. Check them every 6 months. This lesson covers pad thickness, rotor condition, caliper function, fluid health, and the sounds and feelings that tell you a problem is coming before it strands you.
The lesson
What Brakes Do
Disc brakes squeeze a rotor between two pads. Friction stops the car and turns kinetic energy into heat (over 600°F under hard use). Pads wear down — that's normal. Rotors wear too, but slower. The caliper piston extends as pads thin; that's why brake fluid level drops with worn pads.
Visual Pad Inspection
With the wheel off (or peer through the spokes with a flashlight), look at the pad material on the inner and outer side. New pads are 10-12mm. Replace at 3mm. If you see metal-on-metal (the pad backing plate scoring the rotor), you've gone too far and likely need new rotors too.
Rotor Condition
Run a finger across the rotor face (cool only). Light grooves = normal. Deep grooves you can catch a fingernail in OR a thick lip on the edge = needs machining or replacement. Blue/purple tint = severely overheated (warped). Measure thickness with a micrometer against the 'minimum spec' stamped on the rotor.
Caliper & Slide Pin Check
A stuck caliper or seized slide pin causes uneven pad wear (inner pad worn to nothing, outer still thick = stuck slides). Push the piston back in with a C-clamp — if it doesn't move, caliper is seized. Also check rubber boots: torn boot = water in, rust out, future fail.
Warning Signs — Sound, Feel, Sight
Squealing on light braking = pad wear indicator (built-in scraper). Grinding = metal-on-metal, pads are done. Pulsing pedal = warped rotor. Pulling to one side = sticky caliper or uneven pads. Soft/spongy pedal = air or fluid leak. Pedal sinks to the floor over time = master cylinder bypassing internally.
Tool list
- Flashlight
- Brake pad gauge or steel ruler (mm marks)
- Jack + jack stands (to remove wheels for a thorough look)
- Lug wrench
- C-clamp or piston compression tool
- Micrometer (for rotor minimum-thickness measurement)
Safety — Read or get hurt
- !!Don't drive on grinding brakes — you risk total brake failure on a hard stop.
- !!Brake dust contains heavy metals. Don't blow it with compressed air — wear an N95 mask if cleaning.
- !!Test brakes immediately at low speed after any wheel or brake work — pump pedal first to seat the pads if you compressed pistons.
- !!Brake fluid eats paint. Wipe spills immediately.
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