Originally Posted by Fresh1
On bumpy surfaces, I find the (16") ContiProContact to be very rough - while on smooth surfaces they feel soft and a bit squishy. It's as if the extra sidewall and greater air volume in the tire (215-55-16 size) make it super bouncy (i.e. a perfect storm of sorts combined with the steel-wheel weight), so that that the suspension damping cannot absorb the kinetic energy that the bumps impart into the tire, because the tires pass it all to the vehicle (instead of the tire rubber absorbing much of it).
The most likely answer is that our cars have progressive springs, therefore they are soft at low compression (smooth highways) and firm at greater compression (bumps). Pretty typical in European sedans.