The Suspension System of a vehicle determines the smoothness of the ride.  It is made up of shocks, struts, control arms, ball joints and stabilizer bars to name a few.  These items all work together to absorb the impact of driving on bumpy roads or hitting potholes.  As with any other system in your vehicle, the miles accrued on your vehicle, along with how and where you drive, determines how often these items need replaced.  They will usually give you a warning sign, such as a noise or a bumpier ride, at which time you can give us a call so we can take a look at these items.