Brake lag or delayed braking is best described as the time it takes for the brakes to bite after stepping on the brake pedal. Brake lag is most common in trucks, buses, and other large vehicles with air brakes that take about half a second or more to deliver stopping power after pressing the pedal. Although cars with hydraulic brakes should have no perceivable brake lag and are designed work immediately when you engage the brake pedal, neglect or lack of timely maintenance can significantly affect the braking distance of your ride.
Braking distance refers to how far your car travels after applying braking pressure, while stopping distance is the total time it takes for your vehicle to come to a stop after you realize you need to slow down. Stopping distance includes other variables like your reaction time, how hard you step on the brakes, tire condition and tread type, and the time it takes for the brakes to react after you press the pedal. However, a faulty, worn-out, or defective braking system will take longer to stop your car, and that counts as lag.
Worse, quick reflexes and reaction times are not enough to compensate for any brake lag or defects in the system, especially when stopping at higher speeds, on wet roads, or in inclement weather. If you feel the brakes in your car take longer to react or stop the vehicle, the brake pedal feels spongy, or you need to push lower to feel the brakes work, you’re most likely dealing with brake lag, which also means it’s time to give your jalopy some much-needed TLC and a brake service.
What causes brake lag?
You step on the brakes and the car stops — sounds simple, right? In reality, there are many parts hidden from plain view that work in harmony, including the brake rotors/drums, calipers/wheel cylinders, brake pads/shoes, master cylinder, brake fluid, and hydraulic lines. Any part that fades, malfunctions, wears out, or starts leaking can cause brake lag and increase the stopping distance of your vehicle.
For instance, insufficient or contaminated brake fluid can cause low pressure in the system, leading to weak, spongy, or lagging brakes. Brake fluid needs flushing and replenishing every 2 years or 30,000 miles at the very least. The fluid will eventually degrade through heat cycling and moisture contamination, so it’s imperative to only use fresh brake fluid and not fluid that’s been sitting inside an open bottle for who knows how long.
Meanwhile, worn brake pads, a bad brake booster, a faulty master cylinder, or leaking brake lines can all contribute to weak braking or brake lag. Other factors to consider include worn-out shock absorbers, which can affect the tire contact patch and directly contribute to longer stopping distances.
Brake lag versus brake fade: What’s the difference?
Brake lag is a perceivable delay between the time you step on the pedal and when the brakes begin to grab. On the other hand, brake fade occurs when the brakes begin to overheat and exhibit a brief reduction in stopping power. In most cases, you won’t feel the brakes fading just driving around the city or cruising on the highway. It mainly happens if you drive aggressively around a racetrack, although it’s not impossible to overheat the brakes on a normal drive if you push the car hard enough.
Either way, brake lag and brake fade will both make your vehicle harder to stop. Mitigating brake fade in a performance car takes a lot of testing and aftermarket parts, and it typically involves swapping between organic and ceramic brake pads and slotted or drilled brake rotors, as well as replacing brake lines and upgrading the brake fluid.
Meanwhile, the best way to avoid brake lag is by keeping your vehicle’s brakes in tip-top shape. Replacing the rotors when changing the brake pads is a stellar idea, although the brake rotors can typically last longer and require fewer replacements than the pads. As is the case with routine car maintenance, referring to the owner’s manual and adhering to the manufacturer’s recommendations for brake servicing is an excellent way to avoid delayed braking and expensive repair bills later on.
