Brake calipers usually stick or seize because something prevents the piston or slide hardware from moving freely, most often rust, corrosion, failed seals, dirt, or old brake fluid.
Common Causes of Seized Brake Calipers
- Corroded slide pins or guide hardware prevent the caliper from floating and remaining centered, and keep the pads centered and in contact with the brake rotor.
- Seized caliper piston: Moisture and contamination can corrode the piston or bore, especially if the dust boot is torn or missing, or if the brake fluid is contaminated, leading to internal corrosion of the caliper piston.
- Old or contaminated brake fluid: Brake fluid absorbs moisture from the atmosphere over time, and that water promotes internal corrosion in the caliper.
- Torn, dry, or damaged rubber caliper boots/seals: Once the caliper seals fail, moisture and debris get inside, and the caliper pistons can seize.
- Dirt, road grime, or debris buildup: Contamination can keep the slides or piston from retracting smoothly.
- Lack of use: Vehicles that sit idle for long periods are more prone to brake corrosion and sticky brake components.
What it Means
When a caliper seizes, the brake pad can remain pressed against the rotor longer than it should, which creates heat, dragging, uneven pad wear, and possibly a burning smell.
Quick Guide
If one wheel is hotter, smells burnt, or wears brake pads unevenly, the problem is often the brake caliper, the slide pins, or both, not just the pad itself.