Why do car brakes lock up?

October 01, 2021

If your brakes are applying themselves or locking up when you are simply slowing down or when you need them the most, it’s both stressful and dangerous. The invention of ABS (anti-lock braking system) drastically reduced brakes locking up but it can and still does happen. There are also two types of brake lock up that occur. 

Here is why brakes lock up today, what to do if it happens to you and how to prevent it:

Brake drag or self-applying

If you are just driving along and not using the brakes at all when suddenly they start applying themselves, it’s called a brake drag. Leftover hydraulic pressure in the braking system causes your calipers to latch onto the rotor, resulting in braking force. This is something called seized calipers.  

Brake lock-up

A brake lock-up can happen whether you are hitting your brakes hard or gently gliding to a stop, when suddenly your entire braking power is activated. This results in an abrupt and not-so-safe stop. 

What causes brakes locking up?

• Overheated brakes: seized calipers apply constant pressure to your brakes, even when you are not trying to brake, thus overheating them. Overheated brakes can cause lock-up and veer your car to one side of the road. 
• Wrong brake fluid or low brake fluid can cause brakes to lock up. If moisture got into your brake fluid and entered the ABS pump, your brakes will struggle. A brake fluid leak is also very dangerous. 
• Damaged or broken parts in the braking system: worn brake parts and excessive rust on the brakes can contribute to lock-up in normal driving conditions  

How to prevent brake lock-up

Pay attention to your regular maintenance schedule so you know for a fact your ABS is working, you have clean and well-functioning brake rotors and brake pads, and nothing is rusted or seizing. If you’re hearing any noises coming from the brakes, it’s time for a check-up. 

What should I do when my brakes lock up?

Let go of the brake pedal momentarily to give your wheels a chance to gain traction and unlock. Your goal is to regain control of the vehicle. Gently apply pressure to the brakes again if you need it. 

If you don’t have ABS, pump your brakes quickly until you are safely stopped or until the breaks disengage. Then bring in your vehicle to a mechanic right away. Brakes locking up is dangerous and shouldn’t be ignored.