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Summary
  • Brake lag can refer to the natural part of the braking process that occurs after the driver hits the brakes. The other type of brake lag is simply lagging brakes, or brakes that take longer than usual to engage.
  • Possible brake lag causes include worn down brake pads, low or dirty brake fluid, and damaged brake lines.
  • If your vehicle is showing signs of brake lag, visit a trusted mechanic right away to avoid risking a brake lag accident later on down the line. In other words, if the brakes don’t feel right, get them fixed.

The last thing you want in the middle of an emergency is for your brakes to lag. The situation can get very dangerous very quickly and can easily lead to an accident. That’s why it’s best to address brake lag causes as soon as possible. But does “brake lag” mean exactly what its name implies, or is there more to it?

What Is a Brake Lag?

In general, people mean one of two things when they talk about brake lag. On one hand, brake lag can refer to the natural part of the braking process that occurs after the driver hits the brakes. Brake lag figures into the calculations for stopping distance, which is the distance a vehicle travels after the driver wants to stop the vehicle and starts to engage the brakes.

In the stopping distance formula (reaction time + brake lag + braking distance), brake lag represents the time it takes the brakes to engage after the driver steps on the brake pedal. This type of brake lag is especially noticeable in air brakes on larger vehicles like moving trucks. It makes more of a difference in these brake systems. Smaller passenger vehicles don’t typically have much brake lag because they rely on hydraulic rather than air brakes.

Hydraulic brakes aren’t supposed to have much brake lag. They’re designed to work almost instantaneously. If your vehicle is showing signs of brake lag, it’s time to start investigating possible causes so you can address them as soon as possible.

Possible Brake Lag Causes

There are a number of reasons why your vehicle might have brake lag. Many of them have to do with issues in your brake system. To avoid many of these problems, it’s important to keep to your regular maintenance schedule.

Low or Dirty Brake Fluid

Hydraulic brakes run on brake fluid, and it’s essential for this fluid to remain clean and topped up. If not, low levels of brake fluid in the system and contaminated brake fluid can cause brake lag. Keep an eye on your brake fluid and replace it as necessary.

Also check for brake fluid leaks in your system, just in case that’s the reason the fluid’s running low in the first place.

, What Exactly Is Brake Lag?

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: You can measure the brake fluid for moisture by checking it with a voltmeter (from ground to the fluid). More than 0.30 volts measured means water in the fluid. You can use dip Phoenix System dip strips to check for copper content in the fluid.

Damaged Brake Lines

The pressurized brake fluid in your brake system relies on the brake lines to operate. A leak in the lines if they’re rusty can happen suddenly and lead to depressurization, and low pressure means the brakes won’t engage properly, if at all. Road salt and moisture are two main causes for damaged brake lines.

Rubber brake hoses can deteriorate inside and cause issues as well.

Bad Master Cylinder

Your vehicle’s brake master cylinder generates the hydraulic pressure to apply the brakes. Issues with the master cylinder can affect the rest of the brake system. In particular, a faulty master cylinder can cause the front or rear brakes to fail, reducing braking power and increasing brake lag.

Faulty Brake Booster

Brake boosters are meant to provide power assist when the driver depresses the brake pedal, allowing for quicker and easier braking. However, a faulty brake booster can instead lengthen stopping distances and cause poor brake performance. If you observe that your brake pedal is more difficult to press than usual, it could be due to a faulty brake booster.

Faulty Brake Caliper

Brake calipers house both the brake pads and the pistons. They create friction by clamping onto the wheel’s rotors, pressing the brake pads against the rotors to create friction and stop the wheels from spinning. Calipers work as a set and are usually found on both front wheels. If one caliper fails, it can lead to brake lag because there isn’t as much stopping power as there should be.

Brake lag can be a serious problem for vehicles on the road. While many large truck drivers are used to instinctively calculating for brake lag, it isn’t the norm for people who drive hydraulic brake vehicles. If your hydraulic brake vehicle shows signs of brake lag, visit a trusted mechanic right away to avoid possible accidents down the line.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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