I am driving an unmodified 2015 Mercedes E200 Avantgarde. The car drives beautifully except when it goes over some bumps with passengers and I would have to really slow down a lot. Otherwise, the undercarriage hits the bump. The undercarriage will also sometimes scrape the floor when I exit from an underground carpark with a steeper gradient. Is this due to the suspension? If so, what can I do to remedy it?
There are a few speed humps which are mercilessly high. Those aside, a car with standard suspension should generally drive over speed humps without any problem.
Fully laden, there is a remote possibility of scraping at some humps. So the best way to prevent any damage is to be cautious when driving over those yellow and black striped road speed inhibitors.
As for the suspension, a worn spring or damper (shock absorber) can result in lower ride height and excessive bouncing. That could result in the undercarriage bottoming out over humps, and when the car is ascending or descending a ramp.
Usually, it is the exhaust pipe or muffler - the lowest hung assembly under the car - which scrapes the floor. Most of the time, the damage is not serious.
A five- or six-year-old car would normally require the dampers to be replaced. Springs, too, could have weakened over the years, causing the car to sit lower even when unladen, compared with the original ride height.
You might also want to check if there is any undercarriage trimming that may have come loose. These could be hanging lower to the ground. This also applies to the exhaust pipe assembly which, due to a broken hanger, could have dropped a few centimetres.
Have the car hoisted to inspect the state of the undercarriage.