Since I parted out my fixie, I've been riding my road bike. The ride home tonight was soooo smooth, I couldn't believe it. It got me thinking about all the different factors that come into play.
Aluminum is stiff but because it doesn't absorb vibration it is inherently harsh. Steel is flexy and absorbs vibration, Carbon fiber is very stiff but also absorbs vibration, so both give smooth rides. These can be the frames, forks, bars, stems, or seatposts. There is also the matter of tire size, bar wrap or grips, gloves, and your saddle.
So what I'm wondering about is the common range of difference between these factors which can make a bike ride harsh or smooth.
e.g., at what point will similarly aggressive framesets in all aluminum, steel, and carbon match each other's ride quality simply by changing tire size, or bar wrap, gloves and saddle?