Almost certainly your brake rotors are warped. The rotors, sometimes called discs, as in disc brakes, are essentially flat circular plates onto which your brake caliper is mounted. The caliper has a hydraulic piston inside it that pushes the brake pads up against the rotor when you press your foot on the brake pedal driving brake fluid from the master cylinder to the caliper cylinders. However, when the rotor is warped (no longer flat) the pads ride up and down on the hills and valleys on the rotor as it rotates, producing a pulsation, or vibration.

There are two possible cures. One, if the rotors are not too badly warped, and are designed to allow for resurfacing, is to have them planed (sometimes called turned) on a metal lathe. The lathe essentially shaves the rotors back to flat. However, this can only be done if the rotors will still be thick enough after being shaved to still retain structural integrity. The machine shop, or brake shop will measure them to determine if this is possible. If it is not, the alternative is to replace the rotors.

One other thing to consider is that rotors rarely just warp for no reason. Sometimes they warp because the calipers are semi-frozen. Over years of operation the pistons inside them traveling in and out carry minute dust, debris and moisture that cause the inside of the cylinder to corrode, impeding the piston's travel. Then the brake pad does not retreat effectively after you let off the brakes, instead remaining in partial contact with the rotor, generating constant friction and causing it to overheat and warp. This often shows up on the rotor as a bluing scorch mark on the rotor face.

Still another cause, unfortunately, is a recent tire change, in which the shop remounted the wheels with an air wrench. Often this results in over-tightened, or unevenly tightened lug nuts, producing too much, or unevenly distributed lateral stress on the rotor which results in warping.

Rotors warped!!!!

Using cheap aftermarket rotors can have the same issue. I have seen cheap rotors from your large autoparts chains like Autozone, O'Reillys have warped rotors right out of the box.

Have a shop see if there is enough thickness left on the rotors/drums & have them resurfaced

Most times it is not worth the cost of cutting the rotors and there are few shops that do it anymore. So buy new, not cheap or you will be annoyed again real soon.

well on a lighter note don't brake your car! ha ha

rotors are warped.

Honda Accord, 2001. So every time I'm about to break she shakes. If I'm going at a fast speed she shakes more suppose to me going a bit slower and breaking. I changed my breaks less than a month ago and this problem has been going on for a while it's so damn annoying. HELP. Please.