My educated guess is suspension.

An older suspension design will allow significant compression of the front springs which will return to their unloaded condition rather suddenly after the vehicle attains a complete stop on a hard brake action.

On newer vehicles, the suspension won't compress anywhere near as much and the recoil is significantly less.

Simply look at the suspension travel of a W140 vs. a W126. I'll bet the W140 has 3" travel at the very most...........versus nearly 5" on the W126.

What I fail to grasp is how they manage to give the W140 a significantly better ride quality with much less travel. It's not simply a function of it's greater mass.

I had the SD out last night and the ride impressed me as "miserable" yet again. The W126 finds every single pavement undulation and seems to amplify it before it's delivered to the driver.