Why Does My Steering Wheel Shake When Braking?
A shaking steering wheel when braking is not only annoying, it means something is wrong with the brake or steering system. Don't ignore it.
Feeling the steering wheel shake when braking can and should make you nervous. It usually indicates a problem with your brakes, one of your car’s most critical safety systems.
There are two types of brake systems, disc and drum. Since the 1980s, virtually all vehicles come with front disc brakes as standard equipment. Today, most vehicles are equipped with four-wheel disc brakes. Vibrations from out-of-round brake drums are usually felt in the seat or in the rear of the car — not the steering wheel. However (and with car repairs, there’s always a “however”), there are a few other possible causes for a shaky steering wheel when braking. Here’s what you need to know.
How Brakes Work
Stepping on the brake pedal starts a chain reaction. Brake fluid is forced into brake calipers. As the fluid acts on the caliper, the brake pads sitting inside the calipers squeeze the disc brake pads, clamping them down onto the disc brake rotors. The energy of the pads pushing against the rotor generates heat from friction. This heat-friction slows the rotor (and wheel) rotation and ultimately makes the car come to a stop.
Because the disc brake rotors are mechanically coupled to the wheels and suspension system, any vibrations during braking travel up the steering wheel, where the driver feels it.
Disc Brake Pads
Worn, rusted, dirty or loose brake pads cannot effectively clamp down on the rotor. Neither can pads contaminated with oil, brake fluid, mud or road salt, or even grease from a sloppy installation. Any of these can cause your steering wheel to shake while braking. Although there are ways to clean contaminated pads, it’s best to replace them.
Disc Brake Caliper Hardware
Dry, corroded, defective, missing brake caliper mounting hardware — especially caliper guide pins that do not permit the caliper to slide smoothly — will cause the brake caliper to bind and kink, meaning they can’t push the pads squarely against the rotor when applying the brakes. This also leads to the pads dragging on the rotors and overheating, causing them to vibrate when stopping. Pads affected this way may wear faster and unevenly. Replacing pads can be a DIY job, but properly cleaning and lubricating corroded caliper guide pins is a job best left to the pros.
Disc Brake Rotors
Your rotors could be signaling trouble if you feel the steering wheel shaking side-to-side and the brake pedal pulsating up and down when stopping.
A warped disc rotor means the face of the rotor is not a uniform thickness. As the brake pads move over a thinner or thicker area of the rotor when stopping, the brake pedal will move up and down and the steering wheel will shake. As your brake pads press into a rough, rusted area of the rotor, braking and steering will be rough as well. Badly rusted rotors can also cause the brake pads to grab or bind when stopping, causing the steering wheel to shake violently.
Rotor friction surfaces need to be absolutely flat. “Run-out” is a deviation of more than .003 of an inch (.08 mm or the thickness of a human hair) or variation across a rotor’s friction surface, or it can be a side-to-side wobble when looking at the rotor from the front as it rotates. Rotors will wear unevenly, especially if already below the manufacturer’s minimum thickness specifications, if the heat from braking is not quickly dissipated. Rotor wobble is due to rust or grit buildup between a rotor and its mounting surface causing the rotor to wobble.
Even minor rotor defects or cracks will cause shuddering while braking. Serious rotor failures can cause the wheels to lock up and you to lose control of your vehicle.
Overheated brake pads, as well as overtightened lug nuts, are the main reasons for warped rotors. Lack of use, or the environment where you live (salt air and road salts), can cause rotors to rust and corrode. Have a technician do a visual inspection and measure run-out. Rotors can be resurfaced, but if they’re damaged or worn beyond manufacturer’s specifications, they need replacing. It is recommended to replace both rotors on the same axle, and pads, at the same time.
Defective wheel bearings, loose, worn or damaged suspension parts (bushings, springs, struts/shocks, steering linkage, tie-rods) can also cause the steering wheel to vibrate when stopping.
Vibrations from loose or worn wheel bearings will usually be felt in the steering wheel when slowing and turning at the same time. In addition, a defective wheel speed sensor can send misinformation to the computer that will mistakenly activate the anti-lock brake system at any time when stopping. If this happens, it’s time for a trip to the repair shop to diagnose if a suspension part is causing the steering wheel to shake while braking.
Your steering wheel shouldn’t vibrate when applying the brakes. To avoid major and expensive repairs, have your brakes and brake hardware inspected when your vehicle is in for regularly scheduled service or maintenance.