631 I think is the new 531.
853 is a lighter (not necessarily better!) tubing than 631. Well, 853 is stronger than 631 and should weight the same, but because 853 is stronger, theoretically, one can build a lighter 853 frame that is higher than a 631 with same strength.
So it actually depends on the frame and how the builder felt about it.
631 I think is the new 531.
853 is a lighter (not necessarily better!) tubing than 631. Well, 853 is stronger than 631 and should weight the same, but because 853 is stronger, theoretically, one can build a lighter 853 frame that is higher than a 631 with same strength.
So it actually depends on the frame and how the builder felt about it.