Driving With Parking Brake On: What Happens?


Every manual driver will tell you not to even think of driving with the parking brake on. At the very least, it will wear your rear brake pads down, but it could warp or damage your pads, discs or drums, damage the linings or even your tires.

But why does it even happen?

The simplest explanation is often true – people don’t always notice that the handbrake or parking brake is engaged as they begin to drive, especially if there isn’t a red brake light flashing on the panel or (as in some modern autos) a dinging alert sound.

Why It’s Possible To Drive With The Parking Brake On

Your car has two brakes: the foot brake and the parking brake, which is also known as the handbrake/parking brake.The foot brake is very strong because it is hydraulically powered, and needs to be, to stop a fast moving car.

While the parking brake is there to keep your car stationary once it has already stopped, and is therefore much weaker than a foot brake and only locks up the rear wheels.

In fact, it is so much weaker, that if your tried to accelerate with your parking brake on, your engine would easily overpower it. Hence a parking brake would be much worse at stopping a car from driving, and practically useless if you’ve already gotten up to speed.

So the simple reason why its possible to drive with the parking brake on is Because a parking brake offers much less resistance than a foot brake, and is not what its made for. Conquer driving demonstrated it very well in this video below.

Good News First

First, the good news. If you are driving with your parking brake engaged, it likely wont fully lock up your wheels – limiting the amount of potential damage you could cause. Additionally, almost all car nowadays will warn you with a ding noise if you accidentally started driving with your parking brake on.

Driving with parking brake on will definitely make your car move sluggishly – which of course makes you want to pump the pedal harder – but if you catch it in time, the effects are probably limited to wearing down your rear brake pads.

Your front brake pads will not be impacted by your parking brake being on while you drive. The parking brakes act on the rear wheels only.

The other “good” news is that many modern makes and models may not have a conventional parking brake, but rather a push button on the dashboard panel, which may actually limit the possibility of driving off with the parking brake engaged due to alerts.

Many older models may see a red lit up “Brake” sign on the dashboard, though without any alerts sounding. It’s still possible that inattentive drivers may not notice it.

The Bad Possibilities – Mild to REALLY Bad

While parking brakes were originally designed to stop a car when other braking systems failed, the current versions on cars are meant to slow down but not stop the vehicle. This is why its possible to drive with the hand brake applied, though with some difficulty.

Let’s see what happens when you do that.

1. Car Feels Sluggish

The first thing that happens, of course, is that your car will feel very sluggish, or even wobbly. – when you try to drive. It is similar to someone “riding the brakes”, aka driving while simultaneously pressing on the brakes, which is sometimes done to exert control on dangerous turns or rough terrain.

In the case of the parking brakes being on unintentionally, the driver will often press the accelerator even more, exacerbating the other effects.

2. Rear Brake Pads Wear Down

When the brakes are engaged, the brake pads press close to the rotors, generating friction and therefore heat. When the brakes are on continuously and the car drives at some speed, the friction and heat increase proportionately.

The rear brake pads may develop a glaze due to the heat and friction, causing the brakes to function less efficiently and feel spongy. Over time, the glaze should go away.

Prolonged driving with brakes on will cause the rear brake pads to wear down.

3. Brake Fluid Boils

If you continue to drive for a long time with your parking brake on, the heat generated will eventually be transmitted to the brake fluid, which will boil off.

Now you enter into dangerous territory. If the brake fluid has boiled off, the brakes cannot apply pressure to the wheels to slow them down when you do need them to. That can be a recipe for a bad accident.

4. Damage to Drum, Disc or Linings

A long drive with parking brakes engaged can warp or crack a disc or drum. Badly overheated brakes can crack or separate the linings (due to the adhesive melting) from the pads or brake shoes.

You will typically notice a vibration if there is damage to this extent.

5. Potential for Wheel and Tire Damage

While the normal damage will be much smaller, in the rare case that your rear tires fully lock up and somehow manage to drive above 3 miles with the parking brake on, your rear tires could start to smoke and smell because the rubber on your tire is burning from the friction with the ground. If you drove for 1 mile with the parking brake engaged, your tires could wear down, and would require tire balancing.

Related: Should I Balance My Tires Before An Alignment?

So, Should You Be Using the Parking brakes?

The short answer is – absolutely! Parking brakes ease the pressure on the transmission and other systems of the car. As Firestone recommends, the parking brake should be engaged any time the car is parked, whether the car is on flat ground or an incline. For optimum use, the parking brake should be engaged even before the car’s automatic transmission is set into “park”:

Why is the Parking Brake So Important?

When your car is parked, a system known as the parking pawl is engaged, this locks the transmission and effectively stops the car from rolling away.

Over time, the pawl degrades and can malfunction, which would cause the car to roll. Additionally, having the pawl being the sole system keeping the parked vehicle stationary puts pressure on both the pawl and the transmission – especially if you park on inclines. We talked about this in more detail here: Why Won’t My Car Shift Out Of Park?

It is critical, therefore, to form a habit of engaging the parking brakes whenever the vehicle is in park to ease the wear and tear on the car’s systems, just as its critical to disengage the parking brake whenever you drive off the next time.

Types of Brakes

There are generally four types of parking brakes found in automobiles on the road today:

  • Push Button Control – located in the central dashboard with other controls (such as the ignition button) in a newer model car.
  • Center Lever – also found in newer cars, this lever is part of the control systems in the central console placed between the two front shifts with the automatic gears.
  • Foot Pedal (often needs to be pushed to release) – This is pedal located to the left of the other pedals (e.g., accelerator, normal brakes) on the driver side floor.
  • Stick Lever (often to be pulled out to engage and release) – situated to the left of the instrument panel in older model vehicles.

As mentioned above, the older models (e.g. stick levers and foot pedals) sometimes allowed for mistakes, whereas the newer cars often have alerts (pings for example) that will remind drivers if they have not disengaged the parking brakes. Whatever the case, its something to be careful about at all times.

Get Check Ups Done if You’ve Driven with Your Parking Brake On

As mentioned above, if you do drive with your handbrakes on, you need to get some things checked out, including but not necessarily limited to:

  • Rear brake pads
  • Brake fluid
  • Drums, discs, linings around brake pads/shoes
  • Wheel bearings and tire linings

The Final Word

The parking brake ensures the health and safety of your automobile and its critical systems over the long term. So by all means, engage your parking brakes. Just remember to disengage it when you start driving.

If, by chance, you do happen to have driven a few (hopefully, very few!) miles with the parking brakes on, don’t panic unless you spot or smell something obviously wrong. However, it would be a good idea to get your brakes and real wheel checked by a competent mechanic to ensure there is no serious damage. 

If you have any questions or concerns, feel free to leave a comment below.

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