Originally Posted by
Duragrouch
I'll check... my 89 Cannondale was 6061-T6, but that requires post-heat-treatment after welding. Most have gone to 7005 because it doesn't need that IIRC, so less distortion in frame (see link below). I think 7005 is also a bit higher strength. Dahon Mariner, they just call the material "Dalloy Sonus", so no clue, but highly likely 7005 like other bike makers. A big no-no decades ago was 7075, not weldable so often glued into lugs, and it was also more "notch sensitive", susceptible to fatigue failure at a serious scratch.
Thread that talks about 6061 vs 7005, confirms my memory, see post #6:
https://www.mtbr.com/threads/tempera...minum.1053439/
EDIT: Per my memory, 7005 was *specifically designed* for use in bike frames:
https://en.m.wikipedia.org/wiki/7005_aluminium_alloy
Saw the "Dalloy" in their specs....
meh. 6xxx and 7xxx (generally) can be welded and heat treated, but some Dahons had 4xxx hinges to make them lighter and welding is a major no-no.
My main hinge is clicking again and I'm just about over it.
I'll take one more wack at clean/lube/adjustment before I donate the damn thing.
Almost tempted to find a BMX frame and transfer as much of the components as possible.
(I'll get around to doing a geometry comparison one of these days/weeks/years)
This is likely the end of my second Dahon phase.