Brake drum bolts
Hello,
Just been out in the cold garage to measure some bolts.
The bag of about 100 original ones has two types. One has a round eccentric head and is .311 under the head. the others are hex head with 2 reduced sides, these are .309 under the head.
The round head type appears better quality, if you will forgive the pun all round.
5/16 is .3125, 8mm is .3150 so I would think unless some malefactor opened out the holes it would be no go, but I do not have any to measure to check.
Imperial allen bolts have served me well for more than 30 years, ideally they should be bolts not set screws. The only drum failure so far has been the sprocket flange coming clean off at Cadwell. John.