As steel is generally considered essentially immune from fatigue within its elastic limit in real world conditions, I would be surprised to see a properly built and used (only deformations within its elastic limit) 753 frame last any less time than an equivalent 531 frame of thicker guage pipe.
Barring corrosion, crashes or other abuse and assuming the tubes ween't overheated during brazing, shouldn't a frame constructed of 753 or other light guage tubeset last virtually forever with no change in its physical properties?
Kurt Sperry Bellingham WA Incorrect. Steel fatigues when stressed above it's ENDURANCE limit which is less than the yeild or plastic limit. Also this is not average stress but stress at discontinuities or stress concentrations where cracks will initiate. I would not expect a light gage steel frame to last as long as a heavier gage steel frame under high stress. I would assume that a 753 frame will out last a 531 frame of simular gage tubes but the extra strength material is used to enable using lighter tubes. I had a Columbus ALLE R tubed Concorde which failed at the seat tube BB junction a case of using a lower strength material with lighter gage(I think they used SL gages) which lead to a short life. I am not knowledgeable enough about 753 to be sure but I think there were various gages of the 753 tubeset available. Brian Blum in Berkeley
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