Why does the steering wheel shake when braking at high speed?

Updated: March 04, 2020
Many motorists have experienced this problem: The steering wheel starts shaking when brakes are applied at high speed. Often, it's more noticeable when braking on the highway at 60-70 mph.
Steering wheel shakes while braking Unevenly-worn or warped brake discs (rotors) can cause the steering wheel to shake when brakes are applied.
In most cases this issue is caused by warped or unevenly-worn front brake rotors (discs), although there could be other reasons. A brake rotor or disc is the part that is squeezed by brake pads when braking. The working surface of new brake rotors is uniformed all around and the brake force remains the same when the brakes are applied while moving. See the photo of the new brake rotor. An unevenly-worn or warped rotor has thicker and thinner spots, so the brake force changes as the rotor spins. This change in the brake force causes the steering wheel to shake when brakes are applied. When this happens, you may also feel a pulsation in the brake pedal.

This issue can happen with front and rear brake rotors, but the problem with front rotors is more likely to cause the steering wheel to shake. Some cars have drum brakes on the rear axle. Warped or rusted rear drums can also cause brake pedal pulsation.
What can cause brake rotors to wear unevenly? This can happen for a variety of reasons. Very often it happens when the car is parked outside for extended periods of time without moving.
Rust spot on a brake rotor In the car on the left photo, the steering shake and brake pulsation was caused by rust spots on the brake disc (rotor). More illustrations: Fig1. Fig 2.
This causes portions of the brake rotors to rust, especially in rainy weather; see the photo. Rusted brake rotors are one of the common reasons for brake pedal pulsation and steering wheel shake.
The rotors can also warp as a result of excessive heat, generated while braking. This usually happens in heavy cars, trucks, minivans and SUVs. Other reasons include low-quality material of the brake rotors or pads, sticky brake calipers, seized caliper pins or improper installation. What is the solution?

The solution is to visit your mechanic and have your brakes properly inspected. Mechanics have special tools to measure the runout and thickness of your brake rotors (or rear drums). The repair will depend on the results of the inspection.
Brake latheBrake lathe.
In some cases, brake rotors (or rear drums) can be machined (cut), in others, they might need to be replaced.

Most automotive shops have a machine called a brake lathe that can cut a thin layer of a brake rotor or drum material to make the working surface even and uniformed. Machining (resurfacing) two rotors can add $40 to $120 to the price of the brake job. Your mechanic may recommend replacing the rotors if they are too thin to be machined, or for other reasons. Often, replacing two rotors costs slightly more than machining them. Replacing rotors is always a preferred option, since machining makes the rotors thinner. Brake pads and other components may also need to be replaced, depending on the condition. Read more: When do disc brakes need to be replaced?

Is it safe to drive a vehicle if the steering wheel shakes while braking? The only way to get the answer to this question is to have your brakes inspected by a qualified mechanic. Car manufacturers provide specifications and safe wear limits for brake components.
If any of the parts (e.g. brake rotors) are worn beyond the safe limit, the vehicle is deemed unsafe to drive.

How expensive is it to replace brake pads and rotors? The replacement of the brake pads and rotors in an average car costs from $400 to $750 per axle. Replacing rotors only is cheaper. It's always recommended to use only high-quality or OEM parts. Keeping your brakes in top shape is an investment in your safety and the safety of your passengers.