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Grade 5 Grade 8 Grade 2 Bolts

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A grade 5 bolt (center) will have three radial marks on the hex head. Grade 8 (right) will have six marks. Grade 2 (left) will be unmarked or have some other designator. Stick with Grade 5 or Grade 8 bolts (or equivalent metric grades) for automotive use. Tensile strength is greater than yield strength for a bolt. A common misconception is that it’s better to run Grade 5 bolts as opposed to Grade 8 bolts because a Grade 8 bolt is harder and more prone to snap and break where a Grade 5 will stretch more before breaking. However, the higher grade bolt is considerably stronger in both yield and tensile strength. When in doubt, use Grade 8 or better. fw