Current Projects chat and miscellany

i was under the impression that 7075 was the best but am happy to be corrected.

Then let me correct you; there is no such thing as 'best', just the best compromise between various properties. In general, frame tubes are 7005 or 6061, although 7003 and one or two other 6000 series alloys have been used. For a frame, post weld properties are important, which is why they use 7005 and not one of the stronger 7000 series alloys commonly used for parts which don't need welding, such as 7075. All else being equal, 7005 > 6061, but things are not always equal - 7005 is a more expensive material, so a manufacturer could spend more on fabrication with the cheaper alloy and come up with a similar end result at a similar total price. The dominance of particular alloys in the cycle industry is less to do with rigorous optimisation of designs and more to do with marketing and availability of suitable materials from mills supplying bigger industries.