Could anyone help me decide on which alloy to choose for a pair of new cranks?
Apparently the Sugino XD2 cranks are being sold in at least 2 versions: the Sugino branded one in cold forged, anodised 6061 aluminium and the Spa Cycles unbranded one in forged, polished 2014 aluminium (also Sugino made, according to pictures of the stamp on the rear of the crank). The latter alloy is claimed to be of higher strength by the shop, but I have no clue if that makes them more suitable for use as year round cranks on a touring bike (mostly in cold, rainy Western Europe with salt on the roads in winter).
Some quotes from around the web about both alloys:
Wikipedia confirms the higher strength of 2000 series:
Ibex Bicycles says 2014 is impossible to weld, while 6061 is. Has anyone ever welded cranks or is this factor of no importance at all?-2000 series are alloyed with copper, can be precipitation hardened to strengths comparable to steel. Formerly referred to as duralumin, they were once the most common aerospace alloys, but were susceptible to stress corrosion cracking and are increasingly replaced by 7000 series in new designs.
-6000 series are alloyed with magnesium and silicon, are easy to machine, and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach.
Tech-faq.com mentions some advantages of anodizing, which sound important for cranks:There are many other aluminum alloys like 7075 and 2014 that are stronger than both 6061 and 7005, but are not appropriate to making bike frames because they are nearly impossible to weld.
So, could anyone push me in the direction of the better choice, please?Anodized aluminum has several advantages that regular aluminum does not. Anodized aluminum has a much more porous surface that allows adhesives, lubricants, and dyes to be absorbed into the alloy. Anodized aluminum also has better natural protection against corrosion and wear, due to its rougher surface and the thick oxide layer that surrounds it. Likewise, anodizing prevents aluminum from cracking or peeling from regular use.
The price difference is not big enough to make it the deciding factor, unless both are equally good.