Why are bike frames getting so much bigger This is just a general interest kind of question, but I've really been wondering about this lately.  We've had a lot of advancements in bikes over the years, and people are always trying to make them lighter, yet for some reason it seems that the frames keep on getting bigger. Just comparing my old steel road bike to my new aluminum touring bike, here's a quick list of things that are bigger.   


Wider diameter handle bars
1 1/8 inch steerer vs. a 1 inch steerer tube.
Wider seat and chain stays.
All main triangle tubes, but the biggest culprit is the down tube.
Fork is a little beefier.
Stem is almost twice as thick.


After you add all this up, I have an aluminum bike that isn't any lighter than the old steel bike I have.  Why has virtually ever part of the frame been made so much larger?
From metallurgy for cyclists:


  a tube's diameter increases (D), the stiffness increases to the third power of that number (d is the inside diameter). Comparing a one-inch tube and a two-inch tube of equal wall thickness., the fatty is going to be eight times as stiff as the little weenie tube. And the weight will only double. Now does the ride of those Kleins and Cannondales start to make sense?


So wider diameter tubes actually allow for less material to be used for the same amount of stiffness, making for a lighter bike with a similar ride.