oneclick 

Steel has roughly three times the stiffness, three times the strength, and three times the weight of typical aluminium alloys used in bicycle frames, but there is another factor which makes things complicated - the part is a tube.

As such, the stiffness of the PART depends on the distribution of the metal as well as what it is. An aluminium part needs more metal to be as strong; that metal has to go somewhere, and if it increases the section modulus sufficiently that part will be stiffer than the same strength part made of steel. The outer diameter of bicycle fork tubes is not (usually) constrained, hence stiffer forks.

But none of it matters anyway - tyre pressures and compliance dwarf any fork differences (speaking for a friend).

lazarusdal

which is why I run 28mm tires and they make a huge difference ... and smooths out any frame carbon, aluminum or steel but I like my new steel with the very curved fork

hose

miyata 916 94' with aluminum fork

easyupbug 

I have played with fork swapping up and down on a somewhat rough chip seal road with a nice incline/decline to get the speed up at our place with 4 frames. THe Viscount was easy as I had the replacement Tange for the "death fork"; could not feel a difference, but the chrome Tange looked better. My Allez Pro still has the carbon Kinesis on it as I thought it handled the less than desirable road condition slightly better. The Pinarello Treviso still has the stock fork as I could not tell any difference and it was jarring on the red and polished Al groupset. The 979 is in my daily rotation and I was pleased to not find the carbon had any advantage. I believe aesthetics may have had a part in this, the Allez had a modern black 2x10 with black wheels, and the 979 frame fork, head tube and stays and the groupset are nicely polished.