Re: Running Board Brackets
Because of the localized stress I would use at least a grade 5 and probably a grade 8 bolt. You can calculate it by using the weight of the person stepping on the running board and multiplying it by the length of the lever arm. Because of the other bracket taking some of the load as well as the fender, I would reduce the calculated load by maybe a factor of 4 to get close. I don't remember the allowable stress values for each of the materials but they are fairly easy to find. On my coupe both sides were broken and I had to replace the brackets. In addition I added a washer to the bolt head and the nut to spread the stress. I am pretty sure that this was overkill.
Vic
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