Thanks, I learned some metallurgy today from several people's informative responses about different types of steel. If I am reading the bolt-grade-chart correctly in your Bolt-Grad-Chart link correctly , a 12.9 grade bolt actually looks somewhat stronger than grade 8 steel (once you convert between megaPascals and pounds per square inch). I'll see what I can find in 12.9 or grade 8 bolts in my local hardware stores. I think the Campy bolt is M8 x 1 threaded with a 6 mm allen key head. According to Velobase, Campy switched to a wider diameter bolt with an 8 mm allen key head in their second generation Chorus seat posts. Shear strength varies with square of bolt diameter, so I assume they were trying to improve the strength of this component as they updated the group in later years.