from bmx action jan 83 quadangle test
"reynolds 531 tubing was developed specifically for bikes.its available either butted or straight.
the quadangle uses straight tubing.
531 manganese-moly is an alloy.an alloy is nothing more than a mixture of metals to achieve a specific purpose.
like aluminium alloy is very light,chrome-moly is also an alloy.
the metals that are to be combined in a certain alloy are super heated to their melting points,then mixed,then cooled.
and ,if you dont mind a bit of over simplication,thats it,you,ve got your alloy.
manganese-moly is an alloy of cobalt,high speed steel,manganese,molbdenum,nickel,silicon and tungsten.
according to the folks at reynolds,531 tubing will retain a greater amount of its tensile strength after welding than chrome-moly will.
it will also absorb a greater amount of flex stress without fatigue failure.
or to put it another way (again according to reynolds),with manganese-moly you get more strength per pound frame weight than with chrome-moly,or the same strength with less frame weight"
hope it all makes sense