We deal with a slightly different standard of bolt in the structural steel industry, however strength characteristics are very similar. A grade 5 bolt has the same basic chemical and physical strengths and properties as an A325 structural bolt which is used in the vast majority of structural connections of any steel building. Grade 8 bolts are comparable with the rarely used A490 bolt, which are used in situations to sustain large dynamic loading. The chemical makeup of a grade 8 bolt is such that it makes it more brittle than that of a grade 5, therefore it is more susceptible to brittle fracture than a grade 5. A grade 5 bolt with a tensile strength of 120,000psi and yield strength of 92,000psi is quite adequate to sustain the loads applied in this friction type connection. Just my though, which means about this much..