Quote:
Originally Posted by DanEC
I would go with something of medium strength (similar to grade 5 bolts). High strength - grade 8 stuff is more brittle and you want something that will take a hit and deform a little rather than shear off.
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The above statement is 100% untrue and nothing but an internet myth, however, even an ungraded bolt will be stronger than your bumpers so I would worry more about fit than bolt grade. Mcmaster has a wide range of sleeve materials from aluminum to stainless and in a range of wall thicknesses to suit the look you want.
In the case of my bumpers, they are made from 18 gage cold rolled and the mounts are 18 gage hot rolled. The whole mess can be moved by hand and even an aluminum bolt is stronger than the bumper and mount.