Why Does My Car Shake When I apply The Brakes?

Warped Rotors and Brake Vibration

If you're wondering why your car shakes when you hit your brakes, you more than likely have one or more warped rotors behind your wheels. A rotor is the round piece of steel pictured below that your brake pads grab hold of when you hit the brakes.  Depending on your hubcaps, you can usually see your rotors on the inside on the wheel. When a rotor comes out of the factory, it's smooth and even. The brake pads make contact with both side evenly and causes good braking. But what happens over time is that the rotors can become warped, meaning that they loose their smooth, even surface. When that happens, every time you go to hit your brakes, the brake pad encounters a surface that isn't entirely smooth and the braking gets very bumpy.

When you have warped rotors, they loose their sleek, smooth and even surface for braking and your car begins to shake.

What Causes Warped Rotors?

Warped rotors can be caused by multiple things.  As you're driving along, if you ever are forced to brake suddenly from a high speed, the friction can cause a level of heat on the rotor great enough to cause the rotor to warp.  In addition to this, if you're ever driving down a long hill and are constantly having to keep your foot on the brake, the build up in heat can also cause the rotor to become warped.  Another thing I've experienced that has caused rotor damage has been excessive use of brake pads, meaning that the brake pads weren't changed early enough and partial metal on metal friction was allowed to happen.  I've replaced rotors before that have had such deep grooves that you could literally put a marble in them and spin it all around the rotor.  You don't want that to happen to your vehicle.

How to Fix Warped Rotors

When your rotors get warped and your car shakes when you hit the brakes, you have a couple of options.  If you change your own brakes, it will be a lot less expensive to fix the problem than if you take your car to the shop for brake jobs.  If you've been experiencing some shaking when you hit the brakes and you're due for a brake change, then that's the perfect time to deal with your warped rotors.  If the rotors are fairly new then you may not need to replace them.  You can take them off and drive them down to your local auto parts store and have them turned on a special machine that grinds down the outer warped layer of the metal to make the surface smooth and even again.  But there are two things that you need to be warned of when considering this process.

1. If your rotor is too thin the auto parts store won't grind them down for you and you'll have to buy new ones.  This isn't really all that much of a problem since new rotors are generally only about $40 a piece.
2. Make sure you call ahead to schedule a rotor turning appointment.  Sometimes when auto parts stores are swamped, it may take awhile to service your rotors and you'll end up sitting there for a long time.  The process shouldn't take more than 30 minutes or so per rotor, but if the shop is busy, it's just best to call ahead and make sure they can do it quickly for you.

Each auto parts store will probably have a different cost for turning your rotors.  But it shouldn't be more than $25 or so.  So all in all, changing your brakes yourself and having your rotors serviced should cost you less than $100, which is pretty nice.  If you don't service your brakes yourself but take them into the mechanic, tell your mechanic that your rotors are warped and that you want him to turn them for you.  Ask him how much it costs for the process and hold him to it.  Another thing you can do is to go to the auto parts store before you go to the mechanic and buy a set of rotors from the store and then ask the mechanic to replace your rotors when he does the brake job.  It should only be a matter of loosening a couple bolts, so don't let him charge you an arm and a leg for the labor.  Best of luck!

Greg
Auto Tech
www.gregsautotech.com