While researching for my sliders, I found this very educational article on RockCrawler.com:
http://www.rockcrawler.com/techrepor...ners/index.asp
Very interesting read. Hopefully, this will help you pick the right kind of bolts for your rig or accessories (winches, bumpers).
Basically, Grade 8 bolts are stronger than Grade 5 in every measurable way. Grade 8 bolts are NOT brittle.
Here is the conclusion at the end of the article:
Getting back to the original question,