You're driving and notice the car gently pulling to one side, even when you're not braking. At a traffic light you catch a burnt smell, and one wheel rim is noticeably hotter than the others. This isn't worn brake pads - it's very likely a stuck brake caliper. The problem is common, can be dangerous, and if caught early the repair doesn't have to be complicated.
What the caliper does and why it seizes
The brake caliper is a metal housing that wraps around the brake disc. Inside it sits a piston that pushes the pad against the disc when you press the brake pedal. When you release the pedal, the piston should retract and the pad should move away from the disc. On floating-bracket calipers there are also guide pins - two metal sliders that let the caliper shift side to side so it presses both pads evenly.
The problem starts when the piston or the guide pins seize up. The piston corrodes inside its bore and can no longer slide back. The guide pins dry out, lose their grease, and lock up. In both cases the result is the same: the pad stays pressed against the disc even after you've released the brake.
Symptoms that point to a stuck caliper
The most obvious symptom is the car pulling to one side while driving - not just when braking. The seized wheel is being constantly braked, creating drag that steers the vehicle off line. This is easily confused with a suspension or alignment issue, but there's a simple test: after 15-20 minutes of driving, carefully touch each rim. If one is significantly hotter than the rest, that's a clear sign the brake on that wheel is working when it shouldn't be.
Other symptoms include uneven pad wear - one pad on the same caliper thinner than the other. The car may also accelerate sluggishly, because the seized wheel acts like a permanently applied brake that saps engine power and burns extra fuel.
In an advanced stage you'll notice a strong smell of burning brakes, and smoke may appear around the affected wheel. If that happens, pull over as soon as it's safe. Overheated brakes lose effectiveness, and there's also a risk of the brake fluid catching fire.
Why this is such a common issue on roads in BiH
Road salt and abrasive grit spread during winter are the caliper's worst enemies. Salty water works its way under the protective rubber boots (dust seals) on the piston and guide pins, and corrosion does the rest. The climate in Bosnia and Herzegovina - wet winters and wide temperature swings - accelerates the process.
Vehicles that sit for long stretches are especially vulnerable. Seasonal cars, weekend vehicles, or cars that stay parked in a garage for weeks develop piston corrosion precisely because the brakes aren't being used. Paradoxically, regular driving and braking partly clean the disc and caliper of surface rust.
How we check the caliper in our workshop
The inspection starts by raising the car and removing the wheels. We spin each disc by hand and feel whether it turns freely or meets resistance. If the disc won't spin, or spins with a characteristic scraping, that's the first indicator.
Next we check whether the caliper piston can be pushed back smoothly with a special tool. If it resists too strongly or won't move at all, the piston is seized. On floating calipers we also test the guide pins - we pull them out and see whether they slide smoothly or are dry and corroded. We visually inspect the protective rubber boots as well: if they're cracked, dried out, or damaged, moisture has almost certainly gotten inside.
When replacing pads we always check that the piston retracts smoothly and the guide pins slide freely. This is part of the job many workshops skip, and it's exactly where the problem begins.
Can it be repaired, or does the caliper need replacing?
If the caliper housing is undamaged, a rebuild is possible - cleaning the piston, replacing the rubber boots, and fitting a new piston if the old one is too corroded. This is a more affordable solution and on many cars delivers excellent results.
However, on older vehicles where corrosion has reached the housing itself, a new or quality-remanufactured caliper is the safer option. The cost depends on the model and condition - get in touch for an estimate.
It's important to know that calipers are always replaced in pairs - left and right on the same axle. Replacing just one side would cause uneven braking.
How to prevent a caliper from seizing
Prevention comes down to a few things that don't require much effort or money.
- Regular brake fluid replacement. Brake fluid absorbs moisture from the air over time, and that moisture causes internal corrosion. The recommended interval is every 2-3 years, depending on the manufacturer and driving conditions.
- Lubricating the guide pins at every pad change. This is crucial, but only silicone-based grease designed for brakes should be used. Regular grease or copper paste can damage the rubber boots and make things worse.
- Visually inspecting the protective rubber boots on the piston and pins at every brake service. A cracked boot is an early sign that moisture will get in and start corrosion. Replacing a boot in time costs very little but saves you from an expensive caliper replacement later.
- If the car sits for a while, take it for a drive now and then and apply the brakes firmly a few times. This helps scrub surface rust off the discs and lets the piston go through its travel.
A stuck caliper is not a problem that goes away on its own. If you notice any of the symptoms described above, book an appointment and let us check the brakes while there's still time. It's better to react at the first sign than to wait for smoke and the smell of burning.