Originally Posted by
jgedwa
By and large, if the frame is aluminum, there will be minimal flex there. If the frame is made of good steel tubing, there will be little flex there. If the frame is made of hi-ten or low-end Cro-Mo, then there can be a ton of flex there.
jim
Tube thickness and diameter play a large role in determining stiffness in addition to the material. I have two steel framed bikes, one alu bike and one carbon. The two steels are both the stiffest and the least stiff, with the alu and carbon bikes in between. You can make a stiff or flexy frame out of any of these materials.