[Blackbirdws6]

Don't be offended but I'd guess this is just the quality of a cheaper wheel cast and then machined to do it's job. Tolerances won't be perfect. Perhaps the spacers aren't perfectly flat either which could cause uneven stress on the wheel resulting in cracks from you tightening them past recommended. I recall the aluminum wheels in my grandfather's XJS jag being so soft that they would bend if you didn't torque them down right.

In any case, I agree that I'd be concerned with running them with 40 ft lbs on the lugs but going beyond what's recommended could likely lead toward more cracking. Food for thought and recognizing funds aren't there for new wheels. Perhaps fix and sell these and maybe a different set will pop pup that will not be a stretch on the wallet.