Originally Posted by 53-11_alltheway
I can't comment on what frame to get, but this talk of Aluminum being fragile is just not true.
What matters more is the weight of the frame/tubing diameter/quality of construction rather than whether it is steel or Aluminum. They can both be good if built heavy enough.
Steel has a fatigue limit true , but track bikes seem to be used hard (you are not spinning low gears in the saddle like you do with a road bike) . Most of the time you may be exceeding this fatigue limit if you are pounding a big gear out of the saddle depending on how heavy you are and how heavy the steel frame is.
There is a fatigue test call the Efbe test which applies a very high "out of the saddle" load to a road frame for 100,000 cycles. Steel does not do well in these tests for whatever reason. Aluminum does great though. Sure aluminum doesn't have a fatigue limit, but it seems to have a better strength to weight ratio.
Aluminum has a lower fatigue limit than steel. The reason that the aluminum bikes do better in the test is the engineering behind them. Because aluminum has a VERY low fatigue strength, the frame must be built in such a way that it doesn't flex very much. It is much easier to bend a piece of aluminum than it is an equal piece of steel, and if you were to flex the two back and forth, the aluminum would break a lot sooner than the steel would. It is because of these aspects that steel and aluminum frames have their respective reputations. Since steel has a high fatigue limit, and can take more flex, you can use it to design a frame geared more towards providing comfort. Since aluminum fails very easily if it flexes, it must be engineered a lot better. This means either thicker tube walls or larger diameter tubes. Both inrease the frame's stiffness. Thicker tube diamters retain low weight. This is why aluminum "space" frames look the way they do. To make sure that they don't flex so that they don't fail. This is also why they are so responsive. Generally for track, if you are racing, you want a stiff responsive bike. In this case, go with aluminum. If you want a mid level track frame that will be around for years, and is resilient to crashes and the like, go with steel. EFBE test may indicate that steel frames fail before aluminum ones do, but all the old frames that I ever see when i go to the track are all steel.