56cm and 57cm frames are small enough so that even with a 200 or so pound rider 753 should be reasonably stiff.

I know that in the late eighties many framebuilders who used Columbus SL or SLX for smaller frames went with SP down tubes for frames bigger than 58 because SLX was just too whippy.

SL was 0.9/0.6/0.9, SLX was 0.9/0.6/0.9 with the helical reinforcements in the butts, and SP was 1.0/0.7/1.0...

In contrast, 753 was 0.7/0.5/0.7 (top tube) and 0.8/0.5/0.8 (down tube) which would make it flexier than SL or SLX.



All steel alloys from AISI 1020 plain carbon steel to the latest high strength alloys like S3 and 953 have virtually the same modulus of elasticity (~200 GPa) and virtually the same density (~8 grams per cubic centimeter). IOW, an AISI 1020 "gaspipe" tube and a 4130, 531, 753, or 953 tube with the same diameter, wall thickness, shape, butting profile and length will all be equally stiff. Where they differ is in tensile strength and yield strength, and a stronger alloy can be drawn with thinner walls and thus be lighter, but the price of the thinner walls is less stiffness. Want thinner walls and greater stiffness? Increase the diameter (to OS or double OS).

If you look at the 753 data sheet I posted earlier in the thread, it states "The exceptional physical properties of Reynolds 753 allow frame tubes to be produced in wall thicknesses down to approx. 0.3mm, their high stiffness ensuring that top quality frames can be produced with extreme lightness and a high rigidity."

This kind of nonsense, mischaracterizing high yield strength as stiffness, has lead lots of people who should know better to think some steel alloys are stiffer than others. They're not; they're all the same.

Jan Heine did a passable job of explaining it HERE.