A car comprises many parts designed for replacement at intervals during the vehicle's lifetime, due to them wearing out. Brakes, suspension parts, bushings and wheel bearings all wear out over time. The result is a car that has a vague feeling while steering, handling and braking. Worn components can also cause the steering wheel to vibrate or shake, when driving as well as when braking. Steering wheel shake while the brakes are applied can be caused by a variety of problems.
Warped Brake Rotors
By far the most common cause of steering wheel shakes or shimmys while braking are warped brake rotors. The rotors are the round, disc-shaped metal parts on the braking system. When the brakes are applied, the caliper squeezes the brakes pads against the rotor, which slows the vehicle. If the rotors become warped from overheating or excessive use, the result is vibrations that are transmitted to the steering wheel when the brakes are applied.
The solution to warped rotors is replacing or resurfacing them. On occasion, the rotors may be able to be turned on a lathe and machined back to their flat state. Whether or not it is possible to turn the rotors depends on how thick and how badly they are warped. If they need replacing, a mechanic or hardy do-it-yourselfers can install new rotors.
Worn Suspension Components
Another potential cause of steering wheel shimmy and vibration under braking include worn shocks, struts and suspension bushings. If the front shocks are worn beyond their useful life, they may oscillate excessively under braking, causing the wheel to vibrate and shimmy. Worn suspension bushings, particularly the control arm bushings, can also cause the shaking during deceleration. Worn wheel bearings, which support the wheel on the hub, also cause shaking under braking. It should be noted that many of the above problems also cause the steering wheel to vibrate during normal driving..
Replace Worn Shocks and Bushings
If the problem is be worn front shocks, the only solution is removing them and replacing them with new shocks or struts. The same applies to worn suspension bushings, which need replacing to return the car to its normal operating state.
If the front suspension and wheels do not align properly, the result may be shaking and vibrating when braking. The solution is having the suspension properly aligned by a professional alignment shop.