Have you ever been cruising down the road with your car running smoothly, only to find that your steering wheel suddenly starts trembling like a hairless dog on a cold day the moment you hit the brakes? Your immediate thought might be that you’ve driven onto a quake-prone fault line. That’s one possibility, but it’s more likely that there’s something wrong with your car. Now the question becomes, “What causes a steering wheel to shake when braking?” There are several possible answers — some more likely than others.
Vibrations in the steering column can happen for a number of reasons, such as a busted motor mount, bent rims, bad CV joints or loose lug nuts [source: Distad]. But none of these automotive problems would cause a steering wheel to shake only when the brakes are applied. That’s almost always due to a problem with the rotors.
“What’s a rotor?” Good question. Rotors are discs that your brake pads clamp down on in order to stop your car. In other words, they’re pretty important. Why they may cause the steering wheel to shake when braking requires a quick review of how rotors work.
Rotors are usually made of metal and function at a specific width, depending on the make and model of your vehicle. When you apply the brakes, the rotors are exposed to intense heat that must be dissipated evenly across its surface for a smooth stop. However, rotors tend to wear down over time [source: FamilyCar]. As this happens, the metal may become thinned out or warped in certain spots. When the brake pads grip the rotor at high speeds, these imperfections cause a rumbling in the brake pedal that’s then transmitted to the steering wheel.
Solutions for a Steering Wheel That Shakes When Braking
The first step in finding a solution for a steering wheel that vibrates during braking is to determine the cause of the shaking. As we mentioned, this is almost always caused by a problem with the rotors. Other causes of a vibrating steering system would generally cause shaking all the time, not just when braking. With that in mind, we’ll focus this section on the most common rotor problems and their solutions.
One possible cause of vibrations in a car’s wheel is an uneven tightening of the rotors. In that case, you should get yourself to a mechanic who knows how to tighten in a star pattern [source: Distad]. This is an elementary concept that any mechanic worth his or her salt should know. Most will also have a torque stick to measure the tightness of the seal. Keep in mind that every car has its own standard torque specifications, which are generally printed on the rotor itself.
More often, a steering wheel that shakes when braking is caused by warped rotors, which your mechanic may be able to diagnose with a simple test — that is, by spinning the rotors by hand to feel for imperfections. A rotor in good working order should move freely and make a complete revolution without any bumps or signs of resistance areas. If you or your mechanic does notice these issues, you’ve probably got yourself a rotor problem.
For a more definitive diagnosis, your mechanic will need to remove the rotors and measure them with a micrometer. Rough spots or areas that are more worn than others may be re-machined with a lathe. This is called “turning” the rotors, and it shaves off a very thin layer of metal until the surface is smooth again. However, this tactic may not be your best bet. With less metal, the rotor is more susceptible to re-warping, which would likely occur again very soon. In most cases, you’ll need to have them replaced.