Steel vs. Aluminum bicycle frames (Warning: this information may not be popular with new bike sellers who promote Chinese made mass-production low-quality frames). If you appreciated reading this (when done), please give me your vote of approval below to help spread the truth, otherwise it will be deleted by me.

For those of you who are interested, here is some information regarding the difference between bicycle frames made of steel vs aluminum, that shound be, but isn't, common knowledge:

Over eighty six percent of the energy loss on any bicycle is from the flexing of the frame ("the overall loss of the pedaler's energy due to friction in the bearings is found to be less than 1 percent. Chain losses would add 1.5-5 percent". Source: 'Bicycling Science' 2nd ed.). This energy loss depends on the properties on the material used.

In the case of metals, it depends on the properties of them AFTER WELDING. No matter how good or how high tech the metal is, if it isn't welded good, it won't ride good. Two bikes made from the same tubing with the same design will steer the same, but one could be bumpy and hard to pedal and the other one could absorb bumps and be easy to pedal.
The difference is in the weld quality and resultant change in the properties of the metal.

We are mostly talking about steel here; all of our bikes are steel. Here's why:

Some steel bikes ride better that titainium ones, and vice versa; however the special facilities required for the cutting and welding of titainium ($$$$), its price ($$), and its availability (USAF) mean that we cannot use it and meet our goal of a killer handwelded steel bike ($) for the price of an aluminum production bike($).
Steel is a springy metal and aluminum is not (well, how many aluminum springs have you seen?). Aluminum bikes transmit high frequency vibrations (as do, to a lessor extent, poorly welded steel ones) while steel bikes absorb vibrations. The introduction of TIG (Tungsten Inert Gas) welding allowed a reduction of production costs for bikes, however the major impact was that use of an inert gas for welding allowed aluminum to be used for bike frames, despite its obvious deficiencies: transmission of vibration and a failure mode known as 'sudden and catastrophic.'

Economics rules the world. Bike tubing is cheap. Welders are expensive. Aluminum is weak, so a thicker tube must be used. A thicker tube allows the use of a less skilled welder (which is harder to make, a pancake or a crepe?), and this is where the very major cost savings occur.

Also, since thicker tubes are used in aluminum bikes, especially mountain bikes, the weight savings are not as much as one might think. This situation was put into very clear focus a few years ago when one of the bike companies we dealt with offered steel and aluminum mountain bikes at the same price. Our staff, and all customers who made a comparison, found that the steel bikes were a little easier to pedal and less bumpy, even if the steel bikes had no shock (this is because a shock is a low frequency filter but a high frequency pass,ie it does not do away with the undesirable properties of aluminum, just the gross features of the road surface-the 'jittery', high frequency bumps pass thtough the fork and frame to your hands).

Lastly, many bicycles sold on eBay contain recalled parts, like stems, forks, ect, that are not safe. There have been so many parts recalled over the years that even seasoned bicycle professionals cannot be aware of all of them, so please do your homework and ask someone who you know is knowledgeable in the brand of bike or bike part that you are interested in. Some bike parts are bought for their collectability or historical significance by collectors and may not be safe for rigorous riding. My goal is not to scare anyone. In fact,  I want to encourage safe cycling and promote awareness. I hope you got something useful out of this and your vote of helpfullness would be greatly appreciated to keep more coming.

Oh. The steel bikes averaged about a half pound lighter than the aluminum ones. Modern marketing techniques can do amazing things with people's beliefs.