Originally Posted by
Kilroy1988
Well the 853 frames I've had flex significantly less than my 531s have. They don't necessarily draw the tubing so thin that you end up with the same stiffness at the end of the day. Depends on frame angles and tube lengths and standard vs OS and all kinds of other things too, but that's been my experience in general.
853 is supposed to have significantly more strength than 531 but generally you only save about 10% of the frame weight with the thinner tubes. The rest of that strength difference accounts for an increase in stiffness (assuming the frame is designed to accentuate that strength).
As the Reynolds website advertises:
"
This heat-treated version of 631 is the pinnacle of Reynolds ferrous steels.
It allows frame builders to make very strong, stiff frames with a low frame weight
It can be used in a pure 853 frame to produce a very stiff, light frame with excellent performance for a pure road bike."
853 Steel - Seamless Air-Hardening Heat-Treated Steel (reynoldstechnology.biz)
It is stronger, but that's not the same thing as stiffness.
All steel has the same stiffness. Some are stronger, and can be drawn into thinner tubes which will reduce stiffness. Larger diameter tubing will restore stiffness, allowing high stiffness and low weight in comparison to less fancy steel. What reynolds means when they say 853 'allows frame builders to make very strong, stiff frames with a low frame weight' is that the stronger 853 steel can be made into thin/oversize tubing that attains strength/stiffness of smaller diameter tubing that is thicker.
A straight gauge frame of 531 in 0.9mm is stiffer than double butted 0.8mm/0.5mm 853 of the same diameter because the 531 tubing is thicker throughout. But by increasing the diameter of the 853 tubing, you can create a tube that is both stiffer and lighter than the 531. The greater strength of 853 allows for this.