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Have you ever slowed down to a stop approaching a stop sign and it felt like you were sitting in a washing machine? Those nasty shakes are a byproduct of something that’s wrong with your brake system. The good news is that the system is pretty small and the problems are easy to diagnose and fix.
Something is wrong with either your brake pad, brake caliper, brake rotor, or brake fluid. The first step is to find out which of these pieces is giving you trouble, then replace or repair it. Short of the brake fluid, all of these problems can be solved on your own without taking your car to a mechanic.
In this guide, I’ll teach you 8 reasons why your car is shaking when you apply the brakes. In addition, I’ll provide some simple solutions that you can use to fix your car.
Understanding the Braking System
Your car’s braking system is surprisingly simple. It’s just a matter of applying friction to your wheels so they slow down, therefore slowing down your whole car.
It goes something like this:
Brake Pedal
It all starts with the brake pedal. If you don’t know what this is, then you should probably give away your car or sign up for NASCAR.
When you apply the pedal, you move around brake fluid through the brake line.
Brake Lines
The brake lines are tubes that have an incompressible hydraulic fluid in them — namely, brake fluid. When the pedal is pushed, the fluid starts moving toward your wheels.
Essentially, these lines run from your brake pedal to your brake calipers.
Brake Calipers
The calipers are a clamshell that sandwiches your brake pads and rotor. The caliper has a very simple job: open and close upon request.
As it closes, it squeezes the pad against the brake rotor.
Brake Pad
The brake pad is the hero of your whole system. It’s the only part that provides the stopping power that you need to slow down your vehicle.
They’re made of a special rubber concoction. Engineers put together a material that has a ton of friction, but can also last a long time.
Think of a pencil eraser. As you rub it and create friction, the eraser quickly disappears.
If these brake pads were made out of eraser material, they would be good for one use and then need to be replaced. Instead, they’re made with a material that can be used over and over again while wearing away slowly.
These push against your brake rotors.
Brake Rotor
The brake rotor is a large, circular piece of metal. It gets connected to your wheel and sits stationary.
When the pad is pushed against the rotor, the friction slows down your wheels. The rotor needs to be perfectly flat, smooth and made from a hard material in order for this process to work.
Therefore, rotors are made out of metal. They check all the boxes and allow your vehicle to slow down and stop time after time.
Why Does a Car Shake in the First Place?
Shaking is a physical reaction to something being imbalanced or a nonuniform force being applied. When it applies to your brake system, it’s almost always a nonuniform force.
Think about it: if one tire is slowing down a lot faster than the other, then you have a weird mismatch of forces across your car. The result is a shake that the driver can typically feel.
8 Possible Reasons Why Your Car Shakes When Braking
The good news is that you pinpointed the problem a lot. There’s a whole list of reasons why a car might shake, but the fact that you realized it only happens when you’re braking narrows down that list a lot. I can assume something is up with your brake system.
Here are some of the possible reasons why your car shakes when you’re braking along with how to fix it.
1. Brake Pads Need to Be Replaced
I’m going to start with the most common problem and the easiest to fix — brake pads that need to be replaced.
A rule of thumb is that your brake pads should be replaced every 10,000 to 20,000 miles, but that varies a ton between drivers. For example, my mom loves to stomp on the brakes as hard as she can whenever she drives. As a result, she replaces her brake pads way more often than my dad who prefers to coast to a stop.
Whenever friction is applied between your pads and rotors, a thin layer of your pads wears away. If you’re going really fast and slam on your brakes, you might smell burning rubber from your pads wearing away really fast.
A lot of brake pads have a built-in “squealer”. This is a metal piece with a fun function — it makes a high-pitched squealing noise when your brake pad is low. That’s your brake’s way of saying it’s time for a replacement.
When your pads get low or wear unevenly, you might notice a shake as you come to a stop. In either case, the solution is simple.
Solution: Replace both brake pads. Never replace just one brake pad because you’ll experience uneven braking — always replace them in pairs. (For example, replace the driver’s side and passenger’s side brake pads at the same time if you’re driver’s side is low). Note: If you are replacing your brakes very frequently, check the “brake caliper is sticking” section.
2. Bad Brake Rotors
The other part of this pair is the brake rotor. This one is a little less common and more expensive to fix.
If the rotor isn’t perfectly flat or smooth, then you’ll probably notice some vibrations. Any imperfection will create the brake pad to not smoothly rub against the rotor. This, of course, leads to vibration while you’re braking.
If you drive your car through a puddle, the temperature differential can wind up warping your rotors and causing this vibration. That’s why auto experts suggest against driving through any amount of water on the road.
Solution: Remove the tire, caliper, and brake pad then replace the rotors. You can do this project on your own, you won’t need to go to a mechanic.
3. Brake Caliper is Sticking
If you remember, the brake caliper is the piece that pushes the brake pad into the rotor (like Mike Tyson in the “now kith” meme). If the caliper is stuck, it will either refuse to push the two together or forcibly push the two together too hard.
If it’s not pushing and your other wheel’s brake is activated, then you’ll notice a wobble. If it’s pushing too hard and your other wheel’s brake isn’t pushing as hard, you’ll also notice a wobble.
In either case, you’ll feel a noticeable vibration.
In addition, a caliper that’s stuck pushing the brake pad will result in a pad that needs to be replaced way too often. This is because there’s a huge amount of friction on the pad at all times, wearing away the brake pad too quickly.
Solution: Find out why the caliper is sticking. You might need to replace the caliper. In other cases, some WD40 and removing corrosion will work.
4. There’s Some Corrosion or Rust
Corrosion is any car’s kryptonite. It can appear in a lot of different areas and it always leads to some sort of nuisance.
If there’s rust anywhere in your brake system, you might feel your car shake when you apply the brakes. This could be on the caliper, rotor, or even the metal parts of your brake pas assembly.
Physically finding the corrosion is the hardest part. Take a flashlight and do some digging. Try working the mechanical components by hand and see if you feel resistance or notice corrosion.
Solution: The best method is to replace whatever part is corroded. Alternatively, use a rust-removing agent or WD-40 and see if that works.
5. Guide Pins are Dry
If your steering wheel vibrates like crazy as you’re stopping, it could be dry guide pins. These pins go in the caliper and they act like a rail for it to close. It guides the caliper into the pad and pushes it all into the rotor.
The pins have to be lubricated and clean in order to drive the assembly’s motion.
Solution: Remove the caliper and take a look at the guide pins. Clean off any debris, blockage, or corrosion. Lubricate the pins and reinstall the calipers.
6. Air in the Brake Lines
Cross your fingers that you don’t have air in your brake lines. As I mentioned, your brake line is filled with brake fluid that gets pushed and ultimately pushes your calipers.
If there’s air in the lines, then your calipers won’t be depressed as far as they should be. It also causes your brake line to sputter a little bit as it works through the air and displaces it. As a result, you’ll feel some sporadic shakes as you come to a stop.
If this is the case, then you have no option but to visit your local mechanic.
Solution: Have a mechanic bleed your brake lines. This is a method of removing all the air in your lines, leaving you with just brake fluid.
7. Tire Pressure is Wrong
There are also some symptoms that present like brake issues but aren’t actually related. The first one is incorrect tire pressure. If your pressure is too high or low, then you’ll definitely feel some shakes.
At times, you’ll only get shakes within a certain speed range. As you decelerate and go into this speed range, you’ll notice the shakes again.
You’ll know if it’s a tire issue and not a brake one if it also occurs when you accelerate through this speed range.
Solution: Check the health of your tires and adjust the tire pressure accordingly.
8. Alignment or Suspension Issue
The other issue comes from faulty alignment or suspension. This works the same way as incorrect tire pressure: there’s probably a speed range where the shakes are especially bad. As you decelerate to this range, you’ll notice your car shaking again.
If your car is misaligned, the shakes are due to an imbalanced application of force to the road in front of you. Since things aren’t perfectly parallel, you’ll feel the inconsistencies via shakes.
For fault suspension, your car can’t handle the recoiling forces as you drive along the road. You might notice it when you decelerate, but you’ll also feel it as you speed up.
Solution: Take your car to a mechanic and have them do a full diagnosis of your suspension and alignment. Have them correct the issue.
Conclusion
A shaking car is a pretty scary experience, but at least you know some of the common causes along with some solutions. If you want more car repair guides, check out my blog. Be sure to get the tools and accessories that every car owner needs.
