Why Does My Car Shake?

Why Does My Car Shake?

 Why does my car shake?  This is a question I often get asked.  With everything going on under the car this question can be hard to answer without additional information.    Some vibrations can cause safety concerns, others can be just an annoyance.  That’s why it’s important to have your vehicle inspected by an ASE certified repair center to confirm the cause.   Driving vibrations occur when there is a worn /lose component or when there is an imbalance in a rotating part.  Determining how and when the symptom occurs can tell us a little about the vibration and narrow down the possible causes.  Here are a few symptoms to consider and some possible causes associated with each. 

Why does my car shake when I hit the brakes?  This is called brake pulsation.  In most cases it occurs when there is a warped brake rotor or brake drum.  When the wheels are spinning and the brake pedal gets depressed, the brake pads will squeeze a warped rotor and transfer the back-and-forth movement to the suspension and/or steering linkage (if in the front).  This will show up in the passenger compartment as a shaking steering wheel or shaking seat only when braking.  You may even notice the pulsation in the brake pedal itself.  It is also common for the vibration to get worse on longer trips or during hard stops.

Why does my car shake only when I’m on HWY 290?  There are many things that can cause this, but the most common thing we see is tire imbalance.  When you purchase new tires they are mounted and balanced.  Through normal driving the tire will lose rubber due to road friction causing a wear pattern, in turn changing the tires’ balance.   Tire balance is very important to a smooth ride and should be checked about once a year.  If the balance is off, the faster that tire spins the more vibration can be felt, generally becoming most noticeable around the 55 – 65mph range. 

Why does my car shake when I hit bumps or any time the car is moving?  These are the vibrations that throw up red flags and generally are not seen until the vehicle is at a higher mileage.  They can be related to worn driveline or suspension components that could lead to a safety concern and are sometimes joined by clunks, clicks, squeaks, or a growling noise.  Worn CV axles, drive shafts, and wheel bearings can cause a repetitive vibration as the component rotates.  Like a tire, the vibration caused by these worn parts gets stronger the faster they spin.  Worn suspension components such as ball joints, control arm bushings, trac bars, and shocks/struts can cause a more erratic and intermittent vibration that will continue to get worse until a repair has been performed.  Suspension parts keep the vehicle stable and the tires pointed straight.  Like the sole of your shoe reveals that you scuff your heal when you walk, the tire tread wear pattern can tell you if your suspension needs attention.   

Why does my car shake all the time, even when it’s not moving? This could be an engine mount or an engine performance issue.  Engines are designed to operate smoothly but even a balanced engine will have a slight vibration.  The engine and its slight vibration are isolated from the vehicle chasse by engine mounts.  Engine mounts absorb the engine’s vibration using rubber or hydraulic bushings.  When these bushings fail, the engine vibration will transfer to the vehicle chasse and into the passenger compartment.  This vibration can be compounded by an engine performance issue.  If there is a check engine light on or the engine is not performing to standards, the unbalanced rotating mass and internal combustion can significantly increase engine vibration. 

So, if you have ever asked the question “Why does my car shake?” see if you can answer a few questions before you bring your car in for inspection: 

  • When does the shake occur?      
  • How fast are you traveling before you feel it? 
  • How long does it last? 
  • Is there any noise associated with it? 
  • What part of the car do you feel it in? 
  • Does it get worse the longer you drive?
  • Does it occur more at different times of the day?
  • How long has it been happening? 
  • Does it happen every time?

The answers to these questions can tell us a little about the vibration and narrow down the possible causes.  Sometimes it is best to request a ride-a-long with the service advisor to confirm your concerns at drop off.

Finally, locate an ASE certified Repair center that you can trust and get to know the crew.    Keep up with regular maintenance and have a full vehicle inspection including an alignment check and tire balance performed every 12 months to stay ahead of major repairs.  Remember, preventative maintenance is always cheaper than having to perform a repair once something breaks.