The American Racing produced magnesium wheels for Cobras (leaf spring cars) had bolt in forged steel adapters. The adapters were/are much stronger than original AC Cars rear street car hubs. (SAI and AC both came up with stronger alloy rear hubs for racing.)
The original "sports car" design five spoke wheel assembly had bolts into the magnesium center hub from the rear. That arrangement seemed to work well for most applications. I have known owners that have used them for street and road courses for decades without problems.
Legend says and modern owner experiences agree that rear wheels used in serious drag racing would wallow the bolts in the magnesium wheel. The fix was rotate the adapters and bolt through them and use standard magnesium wheel washers and lug nuts. When SAI’s second drag Cobra was prepared it received the new ‘bolt through’ design wheels. The adapters were the same.
